Adult congenital heart disease
Summary
The heterogeneity of adult congenital heart disease requires a thorough understanding of cardiac anatomy as well as common surgical and interventional techniques. Echocardiographic studies should be comprehensive and performed in a structured fashion, to avoid missing important anatomical or functional information. The majority of clinical questions can be answered based on the results of echocardiographic studies, but the echocardiographer should be aware of the inherent limitations of the technique and additional image modalities such as cardiac magnetic resonance and computed tomography should be used when appropriate. Assessment of pulmonary artery pressure and pulmonary vascular resistance may be essential and still requires cardiac catheterization.
Introduction
Echocardiography has emerged as the main imaging modality for assessing adults with congenital heart disease. Some lesions such as atrial septal defect (ASD), congenitally corrected transposition of the great arteries (ccTGA), or Ebstein’s anomaly may not uncommonly be encountered undiagnosed in adult life. The majority of cardiac defects, however, are diagnosed in infancy and childhood in industrialized countries. Therefore, the adult cardiologist is mainly faced with a patient known to have congenital heart disease. Nevertheless, the diagnosis may, for historical reasons, be incomplete or sometimes incorrect and has to be established in adulthood. Hence, a thorough understanding of cardiac anatomy is required and especially for describing complex malformations a structured approach (sequential segmental analysis) is recommended. In addition, as many patients have undergone surgical or interventional treatment, anatomy and physiology are different from that encountered in paediatric cardiology. Beyond the echocardiographic characteristics, we provide a description of the anatomy and pathophysiology of the most common malformations, reference to further imaging modalities, and highlight information required for clinical decision making based on current European Society of Cardiology guidelines. The orientation of echo images in congenital heart disease is currently controversial. Paediatric echo labs have, in part, moved to an anatomical orientation. When congenital heart disease is practised in the adult setting, conventional image orientation—as is standard in adult echocardiography—is generally used. Due to the wide variety of congenital heart disease and the complexity of its imaging only an overview of the defects most frequently seen in adults can be provided here.
Shunt lesions
Atrial septal defect
ASD represents one of the most common lesions in adult congenital heart disease patients (accounting for approximately 8% of congenital heart defects). Due to a lack in early symptoms and subtlety of physical findings, ASDs are often undiagnosed until adulthood. Depending on the location of the communication between the atria, several types of ASDs can be distinguished.
The secundum ASD is by far the most common type accounting for approximately 80% of ASDs. It is located within the region of the fossa ovalis (
Fig. 22.1). In contrast to a persistent foramen ovale (PFO) with its valve-like morphology, an ASD even if it is small, is always characterized by a deficiency of atrial septal tissue. This distinction between PFO and small ASD may not be clear on transthoracic echocardiography (TTE) and may require transoesophageal echocardiography (TOE).
The primum ASD is located near the crux of the heart and accounts for approximately 15% of ASDs. Anatomically, it belongs to the group of atrioventricular septal defects (AVSD), also called partial AVSD or partial atrioventricular (AV) canal, in which there is fusion between the bridging leaflets of the common AV valve and the crest of the interventricular septum (IVS), as is discussed in detail later.
The sinus venosus defects are located in the region of the mouths of the caval veins. The superior sinus venosus defect is much more common (approximately 5% of ASDs) than the inferior one (<1%) and is typically associated with partial (sometimes complete) connection of right pulmonary veins to the superior caval vein.
The unroofed coronary sinus is a rare form of ASD, characterized by a communication between the coronary sinus and the left atrium (LA). It is almost always associated with a persistent left caval vein draining to the roof of the LA. Most ASDs occur sporadically and the aetiology is likely multifactorial. Secundum ASDs may be associated with the so-called Holt–Oram syndrome (heart–hand syndrome) characterized by skeletal abnormalities of the upper limb (an autosomal dominant disease).1
Pathophysiology
ASD typically results in left-to-right shunting with the extent depending on right ventricular (RV) or left ventricular (LV) compliance, defect size, and LA or right atrial (RA) pressure. In a simple ASD, the left-to-right shunt is primarily due to the higher compliance of the RV compared to the LV. Relevant shunt generally occurs with defect sizes greater than or equal to 10mm. RV volume overload and pulmonary overcirculation are the consequences. Reduction in LV compliance or any condition with elevation of LA pressure (hypertension, ischaemic heart disease, cardiomyopathy, aortic and mitral valve disease) increases the left-to-right shunt. Reduced RV compliance (pulmonary stenosis [PS], pulmonary arterial hypertension [PAH], other RV disease) or tricuspid valve (TV) disease may decrease left-to-right shunt or eventually cause shunt reversal resulting in cyanosis. With advancing age, LV compliance decreases and shunt volume increases. Clinically, the majority of patients with a secundum ASD present in their 40s or 50s with increasing exercise intolerance, shortness of breath, atrial fibrillation, or right heart failure (HF).2 Although pulmonary artery pressure (PAP) may be normal, some degree of pulmonary hypertension is expected due to increased pulmonary blood flow. Severe pulmonary vascular disease is rare and Eisenmenger syndrome occurs in less than 5% of patients (arguably those with a coexisting genetic predisposition). In addition to supraventricular arrhythmias and right HF, ASDs may cause paradoxical embolism.
Echocardiographic assessment
Current guidelines highlight the central role of echocardiography in establishing the diagnosis and the haemodynamic relevance of the defect. Shunting at the atrial level should be suspected in the presence of unexplained RV dilation ( Fig. 22.2 and Fig. 22.3). Direct defect visualization should be attempted from a parasternal short-axis (PSAX) view, a modified apical four-chamber (A4C)
view (with the probe displaced medially and tilted to align the atrial septum at an angle with the ultrasound beam), and a subcostal view. A suspected defect should be confirmed with colour Doppler (CD) echocardiography, as small signal drop-outs can represent artefacts (especially if atrial septum and ultrasound
beam are in parallel). In some patients the defect cannot be visualized by TTE (especially in the setting of sinus venosus defects) and TOE should be performed. TOE allows for improved visualization of the atrial septum (especially useful if interventional ASD closure is contemplated) and assessment of pulmonary venous return (anomalous pulmonary venous drainage is common in the setting of sinus venosus defects). TOE is superior to TTE with respect to measurement of defect size, assessment of residual septum morphology, and rim size. The defect should not be assumed to be circular and measurement from different views is recommended. Three-dimensional (3D) echocardiography allows appreciation the defect’s shape. Shunt ratio calculations can be attempted from the time-velocity integral of pulmonary and aortic flow and the according cross-sectional flow areas ( Fig. 22.2; Chapter 5, Equations 5.23 and 5.24), but accuracy is hampered by measurement errors, particularly of the pulmonary dimension. Assessment of the RV volume overload (enlargement of the RV with normal or hyperdynamic function) is preferred to estimate the haemodynamic relevance of an ASD. PAP should be estimated from the tricuspid regurgitation (TR) velocity. In the elderly, prior to ASD closure, particular attention should be paid to the LV systolic and diastolic function. Examples are shown in Figs. 22.3 and 22.4.
![Figure 22.2 Echocardiographic shunt quantification by estimating pulmonary to systemic flow ratio (Qp/Qs). Pulmonary (Qp) and systemic (Qs) blood flow equal the product of stroke volume and heart rate. Stroke volume, in turn, can be calculated as the product of the time velocity integral across the right and left ventricular outflow tract (here demonstrated at the level of the pulmonary artery and left ventricular outflow tract) and the cross-sectional area ([diameter/2]2 × π) at the site of velocity measurement (see Chapter Chapter 5 Non-invasive haemodynamic assessment5, ‘Study of valvular stenosis’). The main limitation of this method is inaccurate measurement of the outflow tract and PA diameter. This measurement error is subsequently squared and leads to incorrect Qp/Qs estimates. If this method is used, the results should be checked for plausibility (signs of RV volume overload and increase of flow in the PA). LVOT, left ventricular outflow tract; PA, pulmonary artery, VTI, velocity time integral.](/oso/fullsizeimage?imageUri=%2F10.1093%2Fmed%2F9780199599639.001.0001%2Fgraphic022002-full.jpg&uriChapter=%2F10.1093%2Fmed%2F9780199599639.001.0001%2Fmed-9780199599639-chapter-022)
Chapter 5, ‘Study of valvular stenosis’). The main limitation of this method is inaccurate measurement of the outflow tract and PA diameter. This measurement error is subsequently squared and leads to incorrect Qp/Qs estimates. If this method is used, the results should be checked for plausibility (signs of RV volume overload and increase of flow in the PA). LVOT, left ventricular outflow tract; PA, pulmonary artery, VTI, velocity time integral.
Echocardiography and treatment decision
Current guidelines recommend ASD closure in patients with a significant shunt defined by signs of RV volume overload irrespective of symptoms. Thus, the decision is generally based on echocardiographic assessment. However, in the few patients in whom echo detects high PAP (>50% of systemic pressure) cardiac catheterization with pulmonary vascular resistance calculation is indispensable for further decision making. If resistance exceeds 5 Wood units (but less than two-thirds of systemic vascular resistance), closure should only be performed if vasoreactivity can be demonstrated after vasodilator challenge or with specific pulmonary hypertension therapy. According to current guidelines ASD closure is also reasonable in patients with previous paradoxical embolism. In the current era, secundum ASDs are generally closed interventionally if TOE demonstrates suitability (ASD with stretched diameter below 38mm and adequate rim of approximately 5mm, although no such rim may be required towards the aorta). TOE and intracardiac echocardiography (ICE) are also particularly helpful for monitoring the catheter intervention. Interventional closure is not an option for patients with sinus venosus or primum ASD (AVSD) and these patients must be referred for surgical closure.
Ventricular septal defect
VSD represents the most common congenital cardiac malformation (accounting for approximately 30% of congenital heart defects). It may be isolated or associated with other conditions, such as tetralogy of Fallot (see later).
Depending on the location of the defect within the IVS ( Fig. 22.5) and the relationship to the so-called membranous septum, VSDs are classified as:
◆ Perimembranous defects (also named paramembranous or conoventricular VSDs).
◆ Muscular defects.
◆ Doubly committed VSD (also called supracristal, subarterial, conal, or infundibular VSD).
text). MS; membranous septum; PV; pulmonary valve.Perimembranous defects border the membranous septum (hence the name) and represent the most common form of VSD (accounting for approximately 80% of defects). The membranous septum forms part of the fibrous body of the heart and borders, both the aortic valve (AoV) and the TV. Perimembranous VSDs, thus, are subaortic and subtriscupid and characterized by fibrous continuity between the AoV and the TV. The defect, however, can extend into the inlet or outlet part of the IVS.
Muscular VSDs account for approximately 15–20% of VSDs and are completely surrounded by ventricular musculature. They can occur within the inlet, apical (trabecular), or outlet portion of the RV. Muscular VSDs can be multiple and if present in large numbers produce the so-called Swiss-cheese septum.
Doubly committed VSDs are characterized by fibrous continuity between the AoV and pulmonary valve (PV) and are located directly beneath the semilunar valves. In normal hearts the PV is supported by a sleeve of free-standing infundibular muscle and is located above the level of the other valves. Therefore, such defects can only occur if there is intrinsic malformation of the RV infundibulum. These defects are relatively rare in Europe (only approximately 5% of VSDs) but are reported to be relatively common in southeast Asia (approximately 30% of VSDs). These defects are typically associated with aortic cusp prolapse (usually the right) and aortic regurgitation (AR) which may be progressive. A deficiency of the AV component of the membranous septum, the so-called Gerbode defect, is a communication between the LV and RA.
The type of VSD has implications for the cardiac surgeon as the location of the conduction system is different between defects, and muscular defects are more likely to close spontaneously.
AR due to prolapsing of the right or non-coronary cusp of the AoV is a recognized complication of doubly committed VSDs and less common in perimembranous VSDs. A double chambered RV represents a rare complication that may develop over time especially in perimembranous VSDs. In this condition, hypertrophy of muscular bundles divides the ventricle into a high-pressure inflow and low-pressure outflow chamber.
Pathophysiology
The direction and magnitude of the shunt depends on the size of the defect and the pulmonary vascular resistance. Small restrictive VSDs are occasionally associated with endocarditis; however, survival of patients has been demonstrated to be comparable to that of the general population. If not operated upon, patients with a large left-to-right shunt may die of intractable HF early in life. Patients who survive this period gradually become less symptomatic because pulmonary blood flow decreases, a consequence of pulmonary vascular disease that has developed because of excessive pulmonary blood flow and pressure overload. Eventually, Eisenmenger physiology will develop.
Echocardiographic assessment
Except in patients with very limited acoustic windows, TTE almost always permits accurate identification of the defect(s) and the haemodynamic impact. Different planes should be used to image the defect. Useful image planes include the parasternal long-axis (PLAX) view (for perimembranous defects with outlet extension, muscular and doubly committed VSDs), the PSAX view at LVOT level (perimembranous, outlet and doubly committed VSDs), short-axis planes (muscular VSDs), the A4C view (inlet VSD and muscular VSDs), and A5C view (perimembranous and muscular). In addition, subcostal views may be useful in identifying defects. As illustrated in Fig. 22.6, perimembranous and outlet including doubly committed VSDs are difficult to distinguish in the PLAX view. However, in the PSAX view, a perimembranous VSD projects to the area of the TV (10 o’clock position), while a doubly committed VSD is located adjacent to the PV (2 o’clock position). Special attention should be given to identify apically located muscular VSDs as these can be difficult to visualize. Indirect (non-specific) signs for the presence of a haemodynamically significant VSD are LV and LA dilation and an elevated RV pressure. As a consequence Doppler peak velocity of tricuspid or pulmonary regurgitation should be recorded in patients with a VSD. The VSD jet may interfere with TR jet and may make it difficult to measure TR velocity. VSD velocity has been proposed for the
estimation of RV pressure by calculating the LV–RV gradient and subtracting it from the systolic systemic pressure. However, VSD velocity often significantly overestimates the LV–RV pressure difference and such calculations may be misleading.
The size of the VSD should be assessed in different planes (as the defect should not be assumed to be circular) on two-dimensional (2D) echocardiography. A high velocity turbulent flow is suggestive of a restrictive VSD and this should be confirmed by continuous wave (CW) Doppler sampling (velocity > 4m/s). In contrast, large non-restrictive VSDs are characterized by laminar or bidirectional flow, with low velocities. Aneurysmatic accessory TV tissue or, rarely, true aneurysms of the ventricular septum may partially or completely cover perimembranous VSDs and flow within this aneurysm may mimic residual VSDs.3,4 In perimembranous defects and especially doubly committed VSDs, the defect may be partly covered by aortic cusp tissue and this may lead to significant AR. TOE plays a minor role in the assessment of VSDs and may be useful in assessing patients with very poor acoustic windows or to distinguish between a suspected VSD and a ruptured sinus of Valsalva. Examples of VSDs are shown in Fig. 22.7.
Echocardiography and treatment decision
Current guidelines recommend VSD closure in patients with significant left-to-right shunt and signs of LV volume overload (with or without symptoms). Patients with progressive AR due to prolapsing of aortic cusps into the defect should be considered for surgery to prevent a need for AoV replacement. All this information can basically be provided by echo. However, in patients with Doppler-estimated PAP greater than 50% of systemic pressure, invasive assessment of PAP and vascular resistance are indispensable. It has been suggested that patients with VSD and established pulmonary hypertension should be considered for closure if there is preserved net left-to-right shunting and pulmonary pressures or pulmonary vascular resistance do not exceed two-thirds of the systemic value.
Atrioventricular septal defects
AVSDs are characterized by a common AV junction with deficient AV septation. The prevalence of the condition among patients with congenital heart disease is reported to range from 2.9–7.4 %.5 In contrast, the prevalence of AVSDs in patients with Down syndrome is around 30%.6
The main anatomical features of the condition are a common ovoid-shaped AV junction, a defect of the inlet ventricular septum, a five-leaflet common valve (left and right mural leaflet, right anterosuperior leaflet, and superior and inferior bridging leaflet), and an unwedged aorta with an elongated LVOT (i.e. gooseneck deformity). Traditionally, AVSDs have been classified into partial (also called primum ASD or partial AV-canal) and complete forms. It is now recognized that partial AVSDs represent AVSDs with fused superior and inferior-bridging leaflets and attachment of these bridging leaflets to the scooped out crest of the ventricular septum. These patients, therefore, have two valve orifices (albeit with a common AV junction) and present with atrial shunting, only. There is, however, a continuum between partial and complete forms. There may be a VSD that is completely or partially covered by valve tissue forming an aneurysmatic basal inlet ventricular septum with or without a restrictive VSD. This is called intermediate AVSD and may—as is a partial AVSD—be encountered unrepaired in adults.
Pathophysiology
The pathophysiology of the condition is largely dependent on the magnitude of atrial and ventricular left-to-right shunting (size of the ASD and the inlet VSD) and severity of AV valve regurgitation. Whereas a patient with predominant atrial shunting will present with RV enlargement (ASD like), LV and atrial enlargement is a hallmark of predominant shunting at ventricular level. In patients with a common AV valve, biventricular enlargement is to be expected. The left-to-right shunt results in increased pulmonary blood flow. Significant shunt at ventricular level typically leads to pulmonary vascular disease with a high likelihood of eventually developing suprasystemic PAP resulting in shunt reversal and cyanosis (i.e. Eisenmenger syndrome). This is particularly common in patients with Down syndrome. Cyanosis can occasionally also occur independently of Eisenmenger syndrome due to streaming effects of venous blood across the defect leading to systemic desaturation.
Echocardiographic assessment
Adults with complete AVSD will, in general, present after repair. If not repaired they are likely to present with Eisenmenger syndrome. The AVSD should be assessed in different views. In the A4C view the defects of the atrial and ventricular septum can normally be clearly visualized. In addition, this view is helpful in quantifying AV valve regurgitation and in assessing ventricular and atrial dimensions. In this view the loss of offset between the TV and MV (in normal hearts the TV inserts more apically compared to the MV) can be displayed and the common AV valve may be apparent. Septal malalignment with straddling and overriding valves should be assessed. Parasternal and subcostal views should be used to visualize the elongation and curvature of the LVOT (obstruction should be excluded). Visualization of the common AV junction and the five-leaflet AV valve should be attempted in the PSAX view. It should be noted that unlike in the normal heart, the LV papillary muscles are abnormally arranged (located in anteroinferior and posterosuperior positions). In some patients chordae converge into one major papillary muscle and this is often called a parachute MV. Further possible anomalies include a double orifice left AV valve. The parasternal and possibly subcostal short-axis views demonstrate the three zones of apposition of the left AV valve and this has been referred to as cleft MV. However, in the setting of AVSD the terms MV and TV should be avoided as this represents a common valve and bears little resemblance to normal AV valves.
In the setting of right AV valve regurgitation, the RV systolic pressure should be estimated. In patients with cyanosis, where abnormal streaming of blood is suspected, a contrast study should be considered. Examples are shown in Fig. 22.8.
Echocardiography and treatment decisions
Surgery is indicated in most patients with AVSD and significant shunts. Echocardiography provides the essential anatomical and functional information. However, in patients with Doppler-estimated PAP greater than 50% of systemic pressure invasive assessment of PAP and vascular resistance are indispensable. Surgical repair should not be attempted in patients with established Eisenmenger physiology.
Re-intervention primarily for residual AV-valve regurgitation, less commonly residual shunting is also primarily guided by echocardiography.
Persistent ductus arteriosus
The arterial duct represents an essential structure of the fetal circulation connecting the left PA with the descending aorta and allowing blood to bypass the lungs. Postnatal functional duct closure occurs within hours after birth, and the duct is normally converted to a fibrous ligament within the first year of life. A persistent ductus arteriosus has been reported to account for approximately 2.4% of patients with congenital heart disease. It represents a vessel with various configurations between the left PA and the descending aorta, distal to the left subclavian artery.
Pathophysiology
Failure of the duct to close results in shunting from the aorta to the pulmonary circulation. The pathophysiology varies depending on PDA size. Small ducts remain generally asymptomatic, while moderate and large PDAs lead to LA and LV volume overload as well as pulmonary hypertension, eventually culminating in shunt reversal and development of Eisenmenger syndrome in patients with large ducts. Further complications include an elevated risk of endarteritis and the potential for aneurysm formation (rare).
Echocardiographic assessment
The PDA should be visualized in a PSAX view ( Fig. 22.9). In addition, a high left parasternal view can be attempted. This shows the characteristic diastolic flow in the PAs on CD echocardiography. The Doppler signal normally reveals a systolic-diastolic flow, however in patients with elevated PAPs the diastolic component may be missing. The diagnosis of a PDA in patients with established Eisenmenger syndrome and slow bidirectional flow can be challenging. Beyond the direct assessment of the duct,
the echocardiographic study should focus on assessing LV dimensions and function as well as estimating PAP (using TR velocity and PDA velocity). PA dilation is typically seen. Pulmonary hypertension and Eisenmenger syndrome may lead to RV hypertrophy, dilation, and ultimately failure. Adults with a small PDA typically present with normal ventricles and PAP. Patients with a moderate PDA may present either with predominant LV volume overload (when they develop HF they may be misdiagnosed as cardiomyopathy) or with predominant PAH and the signs of RV pressure overload (may be misdiagnosed as idiopathic PAH).
Echocardiography and treatment decision
Closure is indicated in patients with a PDA and LV volume overload and can be considered in patients with a small PDA and a continuous murmur with device closure being the method of choice. Echocardiography provides the required information. However, if PAP is estimated to be greater than 50% of systemic, invasive measurement of PAP and pulmonary vascular resistance should be performed. Closure is indicated if PAP and resistance are below two-thirds of systemic levels and should be considered in patients with higher PAP but still left-to-right shunt or demonstrated vasoreactivity. In patients with a small silent duct (visible on echo but without murmur) and those with established Eisenmenger syndrome, PDA closure is not recommended.
Obstructive lesions
Left ventricular outflow tract obstruction
Left ventricular outflow tract obstruction (LVOTO) is most commonly due to valvular aortic stenosis (AS) (accounting for approximately 75% of cases); however, it can also occur at sub- or supravalvular levels and at multiple levels simultaneously (e.g. in Shone syndrome).
Valvular aortic stenosis
The normal AoV is tricuspid. Bicuspid aortic valves are relatively common (the reported prevalence in the normal population ranges from 1–2%) and accounts for the vast majority of congenital cases of valvular AS. Unicuspid or quadricuspid valves are very rare, but when present, may also be associated with congenital AS. Genetic abnormalities have been related to bicuspid aortic valves, and biscupid aortic valves are associated with abnormalities of the aortic wall and are linked to aortic coarctation.7,8 The progression of AS in this setting may be related to mechanical changes due to abnormal valvular shear stress; however, it is nowadays appreciated that pathophysiology of calcific AS represents an active process related to inflammation and fibrosis.9,10
Echocardiographic assessment
Qualitative and quantitative echocardiographic assessment of AS is described in Chapter 14a. The diagnosis of a primary bicuspid valve is often difficult to establish, once secondary calcification and severe stenosis have occurred. TOE is helpful for morphological assessment of the AoV. While highest transvalvular velocities in acquired AS are most frequently obtained from an apical or right parasternal approach, the suprasternal approach is, however, frequently best in congenital AS.
Echocardiography and treatment decision
Diagnostic criteria and therapeutic options for severe AS are largely identical to those used in patients with acquired heart disease (see Chapter 14a). Unlike in elderly patients with calcific AS, however, balloon valvuloplasty may represent a treatment option in selected patients with valvular stenosis and without significant calcification or relevant regurgitation.
Subaortic stenosis
The spectrum of subaortic stenosis ranges from isolated subvalvar fibrous ridges or diaphragms to a diffuse tunnel-like narrowing of the LVOT associated with a hypoplastic aortic root. In addition, subaortic stenosis can occur in patients with an AVSD, a VSD, or Shone syndrome, or may develop after previous surgical repair of these lesions.
Echocardiographic assessment
The subaortic stenosis can usually be well visualized from the PLAX and the A5C view. CD is helpful to recognize the level of velocity increase below the valve. If TTE is inconclusive, TOE should be performed ( Fig. 22.10). In addition to the morphology and the location of the stenosis, Doppler echocardiography should be used to measure peak and mean gradients across the stenosis. Aortic valve morphology and the degree of AR should be assessed as well as LV function and LV hypertrophy which may be out of proportion considering the LVOT gradient.
Echocardiography and treatment decision
Indications for surgical resection of the membrane are based on symptoms, the severity of the obstruction (mean gradient >50mmHg), the presence of AR and its progression, and the presence of LV hypertrophy. Since no prosthetic material is required, surgery may be considered even in asymptomatic patients without LV hypertrophy and with a normal exercise test when the mean gradient is more than 50mmHg. Although diagnostic information required for the treatment decision can be provided by echo, Doppler may in this setting not uncommonly overestimate the LVOT gradient and confirmation by invasive measurement may be required.
Supravalvular aortic stenosis
Compared to valvular or subvalvular AS, supravalvular stenosis is relatively rare. The lesion is typically localized above the aortic sinuses at the level of the sinotubular junction. Most commonly, the lesion occurs as an hourglass deformity with dilation of the distal aorta, although it can also be localized or diaphragmatic. Most often it is seen in patients with Williams–Beuren syndrome, a syndrome characterized by various vascular stenoses associated with typical facial characteristics, although it can also occur sporadically.
Echocardiographic assessment
The supravalvular stenosis can usually be visualized in a PLAX view with focus on the ascending aorta. Doppler echocardiography should be used to measure peak and mean gradients across the stenosis; however, it should be noted that Doppler gradients tend to overestimate the degree of obstruction and they may require invasive confirmation before treatment is contemplated. CD imaging is also helpful in assessing the origin of flow acceleration in relation to the AoV. LV function, degree of hypertrophy, and dimensions should be assessed. Given the generalized nature of the disease a detailed assessment of the aorta (including abdominal aorta) and pulmonary arteries is recommended which requires additional imaging modalities such as cardiac magnetic resonance (CMR) and computed tomography (CT).
Echocardiography and treatment decision
Treatment indications include symptoms in the presence of a mean gradient above 50mmHg, LV dysfunction, and severe hypertrophy. Asymptomatic patients with gradients higher than 50mmHg and no other criteria for intervention may be considered for surgery when the expected risk is very low. Echocardiography can commonly provide the diagnosis. However, prior to surgery additional imaging modalities and invasive evaluation are generally required.
Aortic coarctation
Aortic coarctation is characterized by a narrowing of the aorta close to the area where the arterial duct inserts (distal to the origin of the left subclavian artery) and accounts for approximately 5–8% of all congenital heart defects. Morphologically the lesion can occur either as a localized obstruction (the more common form, ranging in severity from a discrete shelf to a fibrous diaphragm with a pin-hole orifice) or as a hypoplastic aortic segment. Traditionally, aortic coarctation has been classified into pre-, para-, and postductal forms. This is, however, of limited relevance in adults, where the duct is almost always closed and ligamentous. It has been emphasized that the condition is part of a generalized arteriopathy and is commonly associated with other lesions of the aorta, such as a bicuspid AoV (up to 85%), hypoplasia of the arch, additional stenotic areas within the aorta, and anomalies of the head and neck vessels including intracranial aneurysms. Aortic coarctation is more common in patients with Turner or Williams syndrome, congenital rubella syndrome, neurofibromatosis, and Takayasu disease.
Pathophysiology
Severe aortic coarctation will manifest in infancy, while patients with less severe forms or significant collateral circulation may only be diagnosed in adulthood. Signs and symptoms of aortic coarctation in these patients include upper body arterial hypertension, reduced lower body perfusion (cold feet, leg claudication), HF (as a consequence of increased afterload, ventricular hypertrophy and LV failure), aortic dissection (due to increased blood pressure and intrinsic aortic wall abnormalities such as cystic media necrosis11), endocarditis and intracranial haemorrhage (as a consequence of hypertension and due to associated intracranial aneurysms12). The severity of these second organ complications depends on the degree of narrowing and upper body blood pressure.
In the presence of a significant collateral circulation, the gradient across the stenosis may be reduced. Even after surgical or interventional therapy, significant coarctation may recur and signs and symptoms are similar to those discussed for native coarctation. Aortic aneurysms may develop after surgical correction (especially after patch aortoplasty). Upper body arterial hypertension is frequent even after repair without significant re- or residual coarctation. It has been suggested that this is due to abnormal aortic compliance and wave reflection at the site of coarctation repair (and use of prosthetic material) as well as intrinsic endothelial dysfunction in this setting.13,14
Echocardiographic assessment
Echocardiographic assessment should focus on the site of coarctation as well as on possible associated lesions and complications. The aortic coarctation can be visualized from a high PLAX view or a suprasternal view. Depending on the quality of the acoustic window it may provide important anatomic information (localized fibrous shelf or hypoplastic aortic arch), demonstrate turbulent flow at the site of coarctation, and allow the measurement of vessel dimensions. While high systolic velocities are commonly found on CW Doppler, this does not represent a reliable sign of significant coarctation. More characteristic of severe coarctation are high Doppler velocities that continue throughout the cardiac cycle, resulting in a diastolic run-off or diastolic tail phenomenon ( Fig. 22.11). Although a recent study suggested that measurements based on this phenomenon may have nearly ideal diagnostic performance in distinguishing patients with or without significant coarctation, this sign requires preserved proximal aortic compliance (i.e. aortic Windkessel effect) to produce sufficient diastolic forward flow and thus may be false negative in patients with very stiff or hypoplastic proximal vessels.15 In addition, the presence of extensive collaterals makes Doppler signs of coarctation generally unreliable.
Assessment of the LV with quantification of LV hypertrophy is of particular importance. Evaluation of the AoV (bicuspid), the ascending aorta, and the aortic arch are essential part of the echocardiographic work-up.
Echocardiography and treatment decision
In the current era, interventional angioplasty with or without stent implantation has become the treatment of choice for adults with native or re-coarctation at most centres if anatomically suitable.10,16 If morphology appears not suitable for catheter intervention, surgical repair (including ascending-to-descending aorta conduits in complex cases) should be considered.
Intervention is recommended in patients with arterial hypertension and a non-invasive pressure difference greater than 20mmHg between upper and lower limbs. Hypertensive patients should be considered for intervention independently of the gradient if there is more than 50% aortic narrowing relative to the aortic diameter at the diaphragm (on CT, CMR). Whether such patients should be treated without hypertension remains more controversial. Although echocardiography may provide the diagnosis in most patients, the information for treatment decision requires additional imaging with CMR and/or CT as well as assessment of the pressure difference between upper and lower limbs.
Right ventricular outflow tract obstruction
Right ventricular outflow tract obstruction (RVOTO) can occur at subvalvular, valvular, or supravalvular levels. Subvalvular stenosis is frequently associated with other conditions such as double-chambered RV or tetralogy of Fallot. Double-chambered RV represents a rare complication (3–10%) in patients with a (a mainly perimembranous) VSD. Due to hypertrophy of muscle bundles in the direction of the VSD jet, the RV is separated into a low and high pressure chamber. Infundibular stenosis is part of tetralogy of Fallot but may also occur in patients with valvular PS.
Valvular PS is by far the most common type of RVOTO (80–90%) accounting for approximately 9% of congenital heart defects.2 In the majority of cases there is a preserved mobile valve with fused commissures and an obstructed central opening. In this setting the valve leaflets are thin and there is doming of the valve in systole. A dysplastic pulmonary valve, with myxomatous and poorly mobile leaflets is less common (15–20%). Very rarely, valvular PS may be due to a bicuspid pulmonary valve. Valvular PS is frequently associated with post-stenotic dilation of the pulmonary trunk or the pulmonary arteries (mainly in the doming form of PS).
Supravalvular PS or PA stenosis is caused by narrowing of the main pulmonary trunk, PA bifurcation, or pulmonary branches. It is commonly associated with tetralogy of Fallot, Williams–Beuren syndrome, or Noonan syndrome. Stenosis of the main PA may be secondary to previous placement of a pulmonary band.
Pathophysiology
Significant RVOTO leads to increased RV afterload causing RV hypertrophy and this may induce an additional component of subvalvular (dynamic) RVOTO. Symptoms include angina, dyspnoea, dizziness, or syncope, although patients with mild or moderate stenosis usually remain asymptomatic.
Echocardiographic assessment
Echocardiography can visualize the level of RVOTO, delineate PV anatomy, assess RV hypertrophy, and identify coexisting lesions ( Fig. 22.12). Visualization of RVOTO should be initially attempted from a PSAX view, although modified views such as subcostal short-axis views or an A5C view with anterior angulation may be helpful. On 2D echocardiography the morphology of the PV (doming, dysplastic, etc.) should be assessed. In addition, post-stenotic pulmonary dilation should be visualized. If echocardiography cannot provide all morphological details—which is not uncommon—CMR is used to complement the information. CD flow demonstrates narrow turbulent flow across the stenosis and can be used to delineate the level of stenosis. CW Doppler measurements allow assessment of the severity of the stenosis. According to current guidelines RVOTO is considered mild when the peak gradient across the valve is less than 36mm Hg (peak velocity <3m/s), moderate from 36–64mmHg (peak velocity 3–4m/s), and severe when the gradient is greater than 64mm Hg (peak velocity >4m/s). Doppler measurements may be unreliable particularly in patients with tubular lesions, stenoses in series (overestimation of gradient), and in double-chambered RV where it is in general not possible to align jet and Doppler beam (underestimation of gradient). The severity of obstruction should therefore always be confirmed by estimating the RV pressure from TR velocity. RV hypertrophy should be visually quantified and RV systolic function assessed. In patients with previous pulmonary valvotomy the degree of pulmonary regurgitation should be assessed.
Echocardiography and treatment decision
Balloon valvotomy is recommended for patients with significant valvular PS (doming form). In patients with peripheral PS balloon dilation and stent implantation are usually advocated. Surgery represents the mainstay of therapy for all other forms of RVOTO and patients with dysplastic or hypoplastic PVs.
Intervention is recommended with a Doppler gradient higher than 64mmHg regardless of symptoms as long as no valve replacement is required. Asymptomatic patients who require valve replacement should have a RV pressure greater than 80mmHg (i.e. TR velocity >4.3m/s). A Doppler gradient less tan 64mmHg may justify intervention in the presence of symptoms related to RVOTO or decreased RV function or relevant arrhythmias. A more aggressive approach is advocated for patients with a double-chambered RV (due to the progressive nature of the disease). In many patients this information can be provided by echocardiography. If morphology is insufficiently demonstrated, CMR (or CT) may be required. If severity is uncertain invasive confirmation is required (particularly in asymptomatic patients).
It has been suggested that treatment of peripheral PA stenosis should be considered, if diameter narrowing exceeds 50%, RV systolic pressure is above 50mmHg and/or lung perfusion abnormalities are present. Echo can only provide part of this information and additional diagnostic modalities are required.
Complex congenital heart disease
The segmental approach
Although isolated congenital heart defects (such as simple shunt lesions and obstructive lesions) can be characterized by describing their anatomical position within the normal heart, this approach fails in complex congenital heart disease. Some complex cardiac malformations tend to occur in combination and can be described as a syndrome or using eponymous titles. However, a systematic approach is required to unequivocally describe all individual lesions that can coexist in a malformed heart and all their possible combinations. The sequential segmental analysis provides such a framework for describing complex malformation in a systematic fashion. It is equally applicable to patients with simple isolated defects and those with the most unusual complex malformations. In clinical practice it is often avoided in patients with simple defects (such as secundum ASD), though this is only acceptable if a rigorous analysis has been performed, to exclude associated malformations and to ascertain that the arrangement of the cardiac chambers and their connection is normal (i.e. there is—as described later—situs solitus as well as atrioventricular and ventriculoarterial concordance).
For the sequential segmental analysis, the heart is divided in three segments: the atrial chambers, the ventricles, and the great arteries. First, the position of the (morphological) atrial chambers is examined. The most constant feature to distinguish the morphologically right from the morphologically left atrium is the atrial appendage. The LA appendage is long and tubular, whereas the right appendage is triangular in shape with a broad base and a terminal crest. In addition, the coronary sinus is a specific feature of the morphologically LA. Fortunately, the arrangement of the atria is generally consistent with the arrangement of thoracic and abdominal organs. Therefore, radiological assessment of the morphology of the bronchi and imaging of the abdominal organs helps to determine atrial arrangement. There are four possible combinations:
◆ Situs solitus (morphologically LA on the left, morphologically RA on the right).
◆ Situs inversus (morphologically RA on the left, morphologically LA on the right).
◆ Situs ambiguous (isomerism): LA isomerism (two morphologically LAs) and RA isomerism (two morphologically RAs).
As discussed earlier this normally coincides with the arrangement of the bronchi (the left bronchus being long, whereas the right main bronchus short) and the abdominal organs (liver and stomach) ( Fig. 22.13). Mirror imaged arrangement of the bronchi and the abdominal organs would suggest situs inversus, whereas two morphologically left bronchi with a central liver would suggest LA isomerism. Furthermore, the location of the aorta and inferior vena cava (IVC) below the diaphragm (relative to each other and the spine) is generally related to atrial situs. Normally, the aorta is located posterior
and to the left of the IVC. In atrial situs inversus these positions tend to be inversed (aorta to the right). In patients with isomerism, the great vessels lie to the same side of the spine. In patients with RA isomerism, the aorta is located posterior and to the right of the IVC, whereas in patients with LA isomerism, the IVC is generally interrupted and continued via an azygos vein. As a consequence, the aorta lies anterior to the vein. As a general rule (with exceptions), RA isomerism is associated with asplenia and LA isomerism with polysplenia. Also, patients with RA isomerism have total anomalous pulmonary venous connection, whereas LA isomerism is associated with interruption of the IVC and venous return passing via the azygos or hemiazygos veins (a persistent left superior vena cava is frequently found).
text).
Next, the position of the (morphological) ventricular chambers is examined. Various features may distinguish the morphologically right from the morphologically LV. These include:
◆ The RV is characterized by a grossly trabeculated apex and moderator band while the LV is rather smooth.
◆ The hinge point of the septal leaflet of the TV (indicating the RV) is more apically positioned than the hinge point of the MV (echocardiographically recognisable from an A4C view) (see
Fig. 22.18 in ‘Congenitally corrected transposition of the great arteries’ section).◆ There is septal attachment of the tricuspid but not of the MV.
◆ There is fibrous continuity between the anterior leaflet of the MV and the AoV, whereas the PV is elevated by muscular infundibulum above the levels of the other cardiac valves (although the presence of an infundibulum is not necessarily linked to ventricular morphology).
Having identified the ventricular chambers, the connection between the atria and the ventricles is described. In patients with a morphologically left and right atrium and a morphologically left and right ventricle the connection can be concordant (normal) or discordant (abnormal). In patients with isomeric atria, the connections cannot be described as concordant or discordant. Instead connection is mixed and the ventricular topology—the spatial relationship of one ventricle to the other—needs to be described. This is based on the concept of chirality (handedness). If the palm of the right hand could be placed on the septal surface of the RV with the wrist is at the apex, thumb in the inlet and the fingers in the outlet, this is described as right-hand pattern. In patients with a univentricular heart, the connection between the atria and the dominant ventricle can be described as double inlet ventricle, absent right AV, or absent left AV connection. In this setting the morphology of the dominant ventricle needs to be delineated.
Next the junctions between the atria and ventricles should be described. This includes presence of two distinct valves or a common valve, valve morphology, imperforate valves where appropriate as well as straddling and overriding of valves.
As a last step, the ventriculoarterial junctions are analysed and the arterial relationship is described. The ventriculoarterial connection can be concordant, discordant, or double-outlet (with the greater part of both valves supported by one ventricle). The aorta is identified as the vessel giving rise to the coronary arteries and usually the three arch arteries, the PA as the vessel bifurcating into the right and left PA. If one of the vessels occurs in isolation, this is described as single aortic or pulmonary trunk. Alternatively, a common trunk can exist, giving rise to the aorta, the coronaries and at least on pulmonary vessel. The arterial relationship should be described in anterior–posterior and right–left coordinates (e.g. aorta anterior and to the right of the pulmonary artery).
Finally, although not part of the morphology of the heart, its position within the chest should be described (heart located in the left or right chest or midline = laevocardia, dextrocardia or mesocardia), and the location of the apex specified (directed to the left, right, or the midline).
Tetralogy of Fallot and pulmonary atresia with ventricular septal defect
Tetralogy of Fallot represents the most common cyanotic congenital cardiac defect and accounts for approximately 6.8% of congenital heart defects. The defect consists of a non-restrictive VSD (approximating in size the diameter of the aortic root and in 80% perimembranous), overriding aorta, RVOTO and secondary RV hypertrophy. Anatomically, the hallmark of the defect is the anterocephalad deviation of the outlet septum. This abnormal position of the outlet septum accounts for the overriding aorta, and together with the hypertrophy of the septoparietal trabeculations, for the commonly present subpulmonary stenosis. The RVOTO, however, is usually a combination of subpulmonary and valvular obstruction, occasionally also associated with supravalvular PS. The malformation is part of a spectrum that ranges from non-restrictive VSD with overriding aorta but without relevant outflow tract obstruction (so-called Eisenmenger complex) to pulmonary atresia with VSD. In addition, as the degree of aortic overriding varies, the defect forms part of a spectrum with double outlet RV (aortic overriding >50%). Tetralogy of Fallot can be associated with right aortic arch, anomalous coronary arteries, and additional ASD (pentalogy of Fallot) or VSDs. It is increasingly recognized that 15–20% of cases17 are linked to a microdeletion of a region on chromosome 22 (22q11, previously called Di George syndrome) which generally occurs sporadically but carries a 50% of transmission risk to the offspring and is frequently associated with psychiatric disease.
Pulmonary atresia with VSD shares the intracardiac anatomy with tetralogy of Fallot but the RV and the PAs are not directly connected. In the presence of a non-restrictive VSD, these patients generally have a good sized RV and are candidates for biventricular repair. The PAs can be unifocal with confluent good sized PAs supplied by a patent arterial duct; multifocal, with confluent but hypoplastic PAs, supplied by multiple aortic-pulmonary collaterals (MAPCAS); or (at the worst end of the spectrum) multifocal with non-confluent arteries supplied by MAPCAS. Depending on the pulmonary anatomy establishing a connection between the RV and the pulmonary vascular bed is sometimes a challenge.
Pathophysiology
Patients with uncorrected tetralogy of Fallot are cyanotic. Although the non-restrictive VSD and overriding aorta predispose to cyanosis, its severity mainly depends on the degree of infundibular stenosis. Infants with severe infundibular stenosis develop cyanosis hours after birth. In children with less severe infundibular stenosis at birth, development of cyanosis may be delayed to childhood or occasionally patients continue to have only mild cyanosis (so-called pink tetralogy). In the current era patients generally undergo reparative surgery at presentation or when they become symptomatic. Attacks of severe cyanosis are a feature of tetralogy of Fallot, commonly occurring between the age of 6–24 months. Such cyanotic attacks would prompt reparative surgery. Longstanding cyanosis and increased RV afterload also impact on RV function and may predispose to higher incidence of ventricular dysfunction, RV failure and sudden cardiac death, supporting the current practice of early reparative surgery. The patients with tetralogy of Fallot repaired a few decades ago—and now attending adult congenital heart disease services—may have undergone palliative surgery previous to any reparative operations (if any). These early palliations, aimed at increasing pulmonary blood flow, include Blalock–Taussig (BT), Waterston and Potts shunts (for explanation, see later). Palliative procedures may cause PA stenosis or kinking. They lead to LV volume overload and if sized too large to pulmonary vascular disease. As a consequence these procedures have been largely abandoned and primary repair between 6–18 months of age is the rule nowadays, performed with very low perioperative mortality. Reparative surgery consists of VSD closure and relief of the RVOTO and is currently generally performed via a transatrial–transpulmonary approach. In contrast, repair was previously done via a right ventriculotomy and commonly a transannular patch was placed for complete relief of RVOTO. This approach generates an arrhythmogenic substrate in the infundibulum and leads to severe PR.
Long-term outcome after repair is excellent (35-year survival of approximately 85%). Sequelae and complications, however, are not uncommon and include:
◆ Pulmonary regurgitation (PR): previously considered a benign lesion, it is now recognized that, over time, significant PR induces RV dilation, impaired RV function, represents a substrate for (potentially malignant) arrhythmias, and is accompanied by symptoms of HF. Severe PR is the rule in patients after transannular patch repair. The severity of PR also depends on the compliance (Windkessel function) of the pulmonary circulation and is aggravated by PA stenoses. Echocardiographic quantification of PR is described later. CMR allows quantification of PR based on the regurgitant fraction, with a regurgitant fraction of more than 30–45% generally considered severe to free PR.
◆ RV dilation and dysfunction: this is generally related to severe PR. Due to the multipartite anatomy of the RV, CMR is superior to echocardiography in quantifying RV volumes and function (based on EF) and current guidelines for PV replacement rely on CMR measurements.
◆ Residual VSD: it may occur and the haemodynamic relevance should be assessed (signs of LV volume overload and pulmonary hypertension).
◆ LV dysfunction: it may occur as a consequence of RV dysfunction (ventriculoventricular interaction) and may in itself represent an adverse prognostic marker.
◆ Aortic root dilation with AR: it has been described due to intrinsic aortic wall abnormalities associated with tetralogy of Fallot.
◆ Arrhythmias and sudden cardiac death: approximately 50% of patients die suddenly. The propensity for (malignant) arrhythmias is related to haemodynamic substrates, surgical scars and myocardial fibrosis.
Early management in patients with pulmonary atresia and VSD depends on PA size and anatomy. Patients with confluent, good size PAs and a pulmonary trunk are candidates for a Fallot-like repair using a transannular patch. Patients with good size PAs but without pulmonary trunk undergo repair with a RV to PA conduit. Patients with confluent but hypoplastic PAs generally require an arterial shunt or reconstruction of the RVOT (without VSD closure). This should augment PA growth and be assessed at a later stage for repair using a valved conduit. Patients with non-confluent PAs with adequate, but not excessive, pulmonary blood flow in infancy can survive into adulthood without surgery. Some groups advocate a staged unifocalization approach for this challenging group of patients, eventually aiming for a conduit repair.
Echocardiographic assessment
In patients with uncorrected or palliated tetralogy of Fallot, echocardiography demonstrates the anatomical features described earlier. PLAX and PSAX views demonstrate the perimembranous VSD with overriding aorta, the narrowed RVOT, and valvar stenosis ( Fig. 22.14). The size of the PAs should be assessed. The A4C and A5C views allow assessment of the inflow part of the ventricles and should be used to exclude the presence of an associated AVSD and malformations of the AV valves.
In patients with repaired tetralogy of Fallot, echocardiographic assessment should focus on haemodynamic sequelae, the severity of PR, RV dilation and function (for RV function
assessment see ‘Transposition of the great arteries’). The degree of PR is generally best assessed in a PSAX view. Criteria suggesting severe PR include diastolic flow reversal in the branch pulmonary arteries, a dense PR Doppler spectrum with steep decay, termination of the PR spectrum well before the end of diastole, and a broad regurgitant jet at PV level ( Fig. 22.15). In addition, the degree of residual PS should be quantified, a possible residual VSD should be excluded, RV and LV size and function, the degree of TR, aortic root size, and AR should be assessed.
Some patients have undergone homograft implantation for PR and these should be assessed for homograft degeneration (stenosis or regurgitation) employing modified echocardiographic views as appropriate. Patients after transcatheter PV implantation represent an evolving cohort requiring periodic echocardiographic follow-up.
MAPCAs can be recognized as vessels with continuous turbulent flow by CD imaging.
Echocardiography and treatment decision
Current guidelines recommend PV replacement in symptomatic patients with severe PR and/or PS (defined as a peak gradient ≥64mmHg or a TR velocity >3.5m/s). PV replacement should be considered in asymptomatic patients with severe PR and/or PS and additional criteria such as decreasing objective exercise capacity, progressive RV dilation, progressive RV dysfunction, progressive TR, very severe RVOTO (RV systolic pressure >80mmHg; TR velocity >4.3m/s), or sustained arrhythmias. AoV replacement should be performed in patients with severe AR with symptoms or signs of LV dysfunction or dilation. VSD closure is reasonable in patients with residual VSD and signs of significant LV volume overload. Cut-off values for RV volumes to consider elective PV replacement are based on CMR measures and generally range between 150–170mL/m2 for RV end-diastolic volumes and >80mL/m2 end-systolic volumes. Although echocardiography may, in clear-cut cases, provide sufficient information for the decision to intervene, diagnostic work-up should in general include CMR and, depending on the non-invasive findings, cardiac catheterization may be indicated.
Transposition of the great arteries
Transposition of the great arteries (TGA) is characterized by the origin of the great arteries from morphologically inappropriate ventricles (ventriculoarterial discordance), while there is a normal connection between the atria and the ventricles (atrioventricular concordance). The term TGA should not been used in patients with atrial isomerism, as atrioventricular con- or discordance implies the presence of two different morphological atria. Equally, the term should not be used to simply describe
ventriculoarterial discordance or arterial malposition in patients with complex intracardiac anatomy (such as functionally univentricular hearts). In this setting the sequential segmental analysis should be employed and the position of the great vessels described. Owing to the arrangement of the ventricles (d-loop) the condition is sometimes called d-TGA ( Fig. 22.16).
Clinically, TGA is frequently classified as simple (two-thirds of cases) or complex, based on the presence or absence of significant associated malformations. These commonly include a VSD (approximately 45% of cases), significant LVOTO (approximately 25%) and occasionally aortic coarctation.
Most commonly the aorta is located anterior and to the right of the PA (approximately 95% of cases), although, sometimes it may also be located directly anterior or to the left and in very rare cases even posterior to the PA. Unlike in the normal heart (with cross-over arrangement of the vessels), the great vessels run in parallel (side-by-side arrangement) and this helps to make the echocardiographic diagnosis of the condition. Generally the aorta (arising from the morphological RV) is supported by a muscular infundibulum and the PA is in fibrous continuity with the MV. However, infundibular morphology is variable and there may be bilateral muscular infundibula, especially in the presence of a VSD. The anatomy of the coronary arteries is abnormal and variable.
Pathophysiology and early management
The pulmonary and systemic circulations are arranged in parallel and early survival depends on the presence of associated lesions allowing adequate mixing of blood. In patients without significant intracardiac shunt lesions, a balloon atrioseptostomy is generally performed in the first days of life to allow for shunting after the arterial duct closes. Other palliative measures include the creation of a (modified) Blalock–Taussig shunt to improve pulmonary perfusion. Further management depends on the presence of associated lesions (VSD and PS). In the current era, patients with simple TGA undergo arterial switch operation within the first weeks of life. In the era of atrial redirection operations, repair was generally performed later, but within the first year of life. In patients with complex TGA the Rastelli procedure (or alternatives such as the Réparation à l’ Etage Ventriculaire [REV] or the Nikaidoh Procedure) is commonly performed.
◆ Arterial switch operation: this is the preferred option for patients with simple TGA in the current era. It involves transecting the great vessels above the valve sinus. The arteries are subsequently switched, with the bifurcation of the PAs translocated anteriorly to the aorta (Lecompte manoeuvre). The procedure requires re-implantation of the coronary arteries. The morphologically LV becomes the systemic ventricle, avoiding long-term problems associated with a morphologically right systemic ventricle (see later). Although operative survival is good (>95%) and short- to mid-term results are encouraging, long-term complications include supravalvular PS and PA stenoses, requiring reintervention in as many as 10–25% in some series, aortic root dilation and neoaortic valve regurgitation (generally not more than moderate) as well as coronary artery abnormalities with uncertain long-term impact.
◆ Atrial switch operation: two main variations exist, the Senning and the Mustard operation. Both redirect the blood on atrial level, rerouting the systemic venous blood into the LV and the pulmonary venous blood to the RV (
Fig. 22.17). The Senning operation utilizes autologous tissue from the interatrial septum and atrial wall to redirect the blood, while the Mustard operation involves placing a baffle made of synthetic material or pericardium to reroute the blood. Both operations have been largely abandoned in the current era, but were routinely used before the arterial switch became the procedure of choice in the 1990s. Therefore, the majority of adults with TGA currently seen still underwent an atrial-switch operation. Long-term problems associated with the atrial switch operation are related to the baffle creation, surgical manipulation within the atria as well as the fact that the morphological RV becomes the systemic pumping chamber. Complications include baffle-stenosis (mostly located within the superior limb of the systemic venous baffle), baffle leaks, sinus node dysfunction, atrial arrhythmias, RV dysfunction and dilation, (functional) TR, ventricular arrhythmias and sudden cardiac death.◆ Rastelli procedure in patients with complex TGA: the Rastelli procedure utilizes the VSD as part of the LVOT by placing a synthetic patch or baffle within the RV. Thus, the morphologically LV is connected to the aorta and acts as the systemic ventricle. The PV is oversewn and a valved conduit is implanted to connect the RV to the pulmonary trunk. As the lifetime of the conduit is limited and the patients require re-interventions such as surgical replacement or more recently transcatheter valve implantation.
Echocardiographic assessment
Echocardiographic finding vary with the type of surgical procedures described previously:
◆ Atrial switch operation (Mustard or Senning operation): the atrial cavity is divided into a systemic and pulmonary-venous chamber. Obstruction of the superior caval vein pathway is relatively frequent. It can be asymptomatic if the blood drains to the IVC via the azygos system. It may be difficult to visualize on TTE (subcostal view) and establishing the diagnosis frequently requires TOE or CMR/CT. Obstruction of the IVC can in general be evaluated by TTE but is less common. Obstruction or narrowing of the venous channels should be excluded, as they are nowadays commonly amenable to percutaneous stent implantation. The venous chambers should be imaged by 2D echocardiography; however, Doppler echocardiography is usually required to fully assess baffle patency as well as leaks. A4C view adjusted and tilted to follow the systemic and pulmonary venous flow to the AV valves, subcostal views and tilted PLAX and PSAX views are helpful. Flow disturbance on CD with non-phasic flow and Doppler velocities greater than 1.5m/s are generally suggestive of an obstruction. Flow velocities in the inferior and superior vena cava should be similar. Pronounced discrepancy in flow velocities, therefore represent an indirect sign of stenosis. Obstructions of the pulmonary venous channel are rare. This should be suspected when there is flow disturbance on CD with non-phasic flow, dilated pulmonary veins and narrowing of the pulmonary venous channel.18,19 A recent study suggested, that routine echocardiographic assessment fails to detect systemic venous baffle obstruction in approximately 50% of patients when compared to invasive haemodynamics and venograms.20 Therefore, additional imaging, primarily CMR, should be used to evaluate venous pathways. Contrast echocardiography may assist in the diagnosis of baffle stenoses; however, its main role is in the assessment of baffle leaks. In the absence of a significant stenoses of the superior baffle, the systemic venous atrium should be contrasted within a few heartbeats after injection of echo-contrast in a cubital vein. If contrast appearance is delayed, and contrast enters the atrium through the inferior baffle, this is suggestive of superior baffle obstruction. If contrast appears in the pulmonary venous chamber and the systemic ventricle within seconds this is suggestive of a baffle leak. TOE is a useful adjunct in identifying pulmonary venous limb stenosis.21 Echocardiography confirms ventricular arrangement. Size and function of the systemic right (subaortic) ventricle should be assessed. Quantification of RV function is usually performed as described in
Chapter 11. Especially in the setting of RV dilation, functional TR is common. It complicates assessment of RV function as afterload is reduced and even minor reduction in RV function may represent significant myocardial dysfunction. In addition, residual VSDs and sub-pulmonary LVOTO (due to leftward bulging of the IVS and systolic anterior movement of the MV) should be excluded. The malposition of the great arteries, with the aorta and PA running in parallel is generally evident on TTE ( Fig. 22.17).◆ Arterial switch operation: echocardiographic evaluation focuses on evaluation of aortic root dimensions, presence and severity of AR, and narrowing of the PA at the anastomotic site or in the branches. Doppler measurements may be useful in assessing the severity of stenosis, but should be cross-checked with systolic RV pressure estimated from TR velocity. In addition, LV function, ostia of the coronary arteries, and their proximal course should be assessed. Stress echocardiography may detect inducible myocardial ischaemia.
◆ Rastelli operation: biventricular function should be assessed. Residual VSDs are often difficult to assess, due to the unusual course of the conduit or patch used to connect the LV to the AoV. Doppler gradients across the conduit may be difficult to measure and may be unreliable. Therefore, RV pressure estimation from TR velocity is of particular importance for assessment of conduit stenosis.
Echocardiography and treatment decision
After atrial switch operation, surgical therapy is recommended for severe TR in symptomatic patients with preserved systolic systemic ventricular function. Stenting should be performed in symptomatic patients with significant baffle obstruction and should be considered in asymptomatic patients. Occlusion of baffle leaks should be performed in symptomatic patients with relevant right-to-left (cyanosis) or left-to-right shunt (HF) and should be considered in asymptomatic patients. Subpulmonary outflow tract obstruction should only be addressed surgically when patients are symptomatic or subpulmonary ventricular function deteriorates. In patients post arterial switch operation, complications such as relevant PS or AR should be addressed according to current guidelines. In patients with previous Rastelli repair, conduit stenosis requires intervention in symptomatic patients with RV pressure greater than 60mmHg (TR velocity >3.5m/s). Intervention should be considered in asymptomatic patients with severe stenosis or regurgitation, if additional criteria are present such as decrease in objective exercise capacity, progressive RV dilation, progressive RV dysfunction, progressive TR, severe RVOTO (RV systolic pressure >80mmHg; TR velocity >4.3m/s) or sustained arrhythmias. Although echocardiography will in many patients provide the first hint that reintervention may need to be considered, final decisions will, in general, require additional diagnostic work-up including CMR (CT) and invasive study.
Congenitally corrected transposition of the great arteries
Congenitally corrected transposition of the great arteries (ccTGA) is a rare condition (approximately 1% of congenital cardiac malformations) characterized by a combination of atrioventricular and ventriculoarterial discordance ( Fig. 22.16). As a consequence, the morphological RV supports the systemic circulation. The great arteries are parallel to each other with the aorta commonly located anterior and to the left of the PA. The majority of patients (approximately 90%) have associated cardiac defects such as VSDs (50%, usually perimembranous), PS (30–50%), malformations of the TV (90% at autopsy, including Ebstein-like malformation), and conduction system abnormalities.
Pathophysiology
The systemic and pulmonary circulations are arranged in series. Early symptoms and haemodynamic problems are due to associated malformations. With time, increasing TR, systemic RV failure and arrhythmias develop even in patients without significant associated malformations.
Echocardiographic assessment
Echocardiography demonstrates the RA, receiving the systemic venous return, draining into the morphologically LV. Usually there is fibrous continuity between the MV and the PV. The LV drains into the PA. The morphological RV has a left hand topology (thus the lesion is commonly called l-TGA) and drains into the aorta (usually anterior and to the left of the PA), which is usually supported by a muscular infundibulum. Echocardiography normally reveals these features. The malformation is easiest recognized in the A4C view when looking at the characteristics of a left versus right ventricle (see ‘Segmental approach’ and Fig. 22.18). Evaluation of the systemic TV is of particular importance. Secondary regurgitation (due to systemic RV failure) may be difficult to separate from organic TR unless Ebstein-like malformation is obvious. Associated lesions including VSD, ASD and RVOTO can be identified. Evaluation of systemic RV size and function should be attempted but remains challenging (see ‘Transposition of the great arteries’).
Echocardiography and treatment considerations
Surgical therapy should be considered for severe TR before systemic ventricular function deteriorates (ejection fraction >45%). Haemodynamically-relevant associated lesions should be addressed. Cardiac resynchronization therapy is experimental. Although echocardiography will in many patients provide the first hint that intervention may need to be considered, final decisions will, in general, require additional diagnostic work-up including in particular CMR.
Ebstein’s anomaly
Ebstein’s anomaly is a malformation of the right heart, characterized by rotation and apical displacement of the tricuspid orifice into the RV. The leaflets are markedly abnormal. The anterior leaflet is frequently large and sail-like with abnormal chordal attachments to the RV wall, whereas septal and posterior leaflets are displaced towards the RV apex and often tethered to the endocardium. This commonly leads to TR (of variable degree), but may occasionally also be associated with tricuspid stenosis (TS). The apical displacement of the functional valve annulus results in an atrialized portion of the RV and variable reduction in the size of the functional right RV. Associated lesions include abnormalities of the mitral valve, shunts at atrial level (ASD or PFO in >50% of patients) and accessory conduction pathways (approximately 25%), as well RVOTO, VSD and coarctation.
Pathophysiology
The pathophysiology is mainly determined by the degree of TR, the degree of atrialization of the RV, contractility of the remaining functional RV and LV, the magnitude of atrial left-to-right or right-to-left shunting, and the presence of relevant arrhythmias. Overall, the haemodynamic and clinical spectrum is broad.
Echocardiographic assessment
The level of insertion of the septal leaflet of the TV should be recorded from an A4C view ( Fig. 22.19). An apical displacement—measured as the distance between the hinge points of the septal leaflet of the tricuspid and anterior leaflet of the MV—greater han or equal to 0.8cm/m2 body surface area (BSA) is suggestive of Ebstein’s anomaly. In addition, the size of the anterior leaflet, possible fenestrations, tethering of the septal and posterior leaflet on the septum and ventricular wall should be evaluated in apical, modified (medially angulated) PLAX, and subcostal views. The size of the atrialized and functional RV should be assessed from different views. An area of the functional RV less than one-third of the total RV area is related to worse prognosis and may preclude surgical repair. The severity of TR should be evaluated based on morphology and CD imaging. Systolic flow reversal in the superior and inferior vena cava and hepatic veins can confirm the diagnosis of severe TR. Occasionally redundant anterior leaflet tissue leads to dynamic obstruction of the RVOT and this should be excluded on Doppler echocardiography. Particular attention should be paid to LV size and function, as Ebstein’s anomaly may be associated with LV dysfunction (due to interventricular interaction or intrinsic LV abnormalities, such as non-compaction myocardium). Atrial shunt lesions are common in Ebstein’s anomaly and may cause cyanosis or desaturation on exercise. TOE and/or contrast echocardiography with Valsalva manoeuvre should be used for evaluation.
Echocardiography and treatment decision
TV repair should be performed in symptomatic patients with severe TR if anatomy is suitable and the functional RV is adequate. Repair should be considered independently of symptoms in patients with progressive right heart dilation or reduction of RV systolic function. Generally surgical repair is challenging and should only be performed in centres with specific experience with this complex lesion. Echocardiography in general provides the diagnosis and morphologic characteristics for treatment decision. CMR may be helpful particularly when echo image quality is poor.
Univentricular heart
A wide spectrum of conditions may be associated with a functionally univentricular heart. Although there is only one dominant functional pumping chamber, a second rudimentary chamber is nearly always present. In patients with a functionally univentricular heart, a sequential segmental analysis should be performed due to the complex anatomy and the multitude of associated malformations. Examples of conditions with a functionally univentricular heart include double inlet LV and RV, tricuspid atresia, hypoplastic left heart syndrome, hypoplastic right heart syndrome (e.g. pulmonary atresia with intact ventricular septum variants), and unbalanced AVSDs. These conditions are always associated with additional cardiac lesions including ASD and VSDs, PDA, LVOTO, RVOTO, aortic coarctation, discordant ventriculoarterial connections, atrial isomerism (with associated abnormal systemic venous and pulmonary venous return), and abnormal lung perfusion (such as MAPCAs). The morphology of the dominant chamber should be assessed based on the criteria discussed previously. Although beyond the scope of the sequential segmental analysis, the location of the chambers may provide clues to chamber morphology. The ventricle located anterior and superior is generally a morphological RV, whereas the LV is located posterior. Features of pathophysiological and prognostic importance include the degree of AV valve regurgitation and the presence of a restriction to pulmonary blood flow. Generally, unrestrictive pulmonary blood flow may lead to overt HF due to ventricular volume overload and is associated with the development of severe pulmonary vascular disease which may be prevented by PA banding. Restrictive pulmonary blood flow is generally preferable, but if pulmonary blood flow is too low and cyanosis is severe, a surgical systemic-to-PA shunt (such as a Blalock–Taussig shunt) may have been required.
The double inlet left ventricle (DILV) is the most common form of univentricular heart in adults and is discussed to illustrate some of the principles and pitfalls of echocardiographic evaluation ( Fig. 22.20). The diagnosis implies that more than 50% of the circumference of both AV valves is related to the morphologically LV. The atrial situs should be determined based on morphological features (see earlier), bronchial and abdominal situs. The morphology and function of the AV valve (there can be two valves or one common valve) requires attention. AV valve regurgitation is common and if severe it is prognostically adverse. The rudimentary (morphological right)
chamber is usually located anteriorly and superiorly. The size of the VSD (also called foramen bulboventriculare) connecting the dominant and the rudimentary chamber should be assessed. Most commonly the ventriculoarterial connections are discordant with the aorta arising anteriorly from the rudimentary RV, also called outflow chamber, and the PA from the dominant LV (posteriorly). A non-restrictive bulboventricular foramen is, therefore, required for unobstructed blood flow into the aorta. The degree of PS should be assessed as this has pathophysiologic and prognostic implications.
Patients with functionally univentricular hearts are unsuitable for biventricular repair and a number of palliative procedures have been introduced.
Palliative procedure to reduce pulmonary blood flow
Pulmonary artery banding: a surgically created stenosis of the main PA to protect the pulmonary circulation from pulmonary vascular disease due to high blood flow and pressure. This palliative procedure is used when definitive correction of the underlying anomaly is not possible or not immediately advisable.
Palliative procedures to increase pulmonary perfusion
◆ Blalock–Taussig (BT) shunt: the classic BT shunt represents an end-to-side anastomosis between the subclavian artery and the ipsilateral PA. The modified BT shunt uses interposition of a graft between the subclavian artery and the PA.
◆ Waterston shunt: side-to-side anastomosis between the ascending aorta and the right PA. Due to the high incidence of pulmonary hypertension this procedure has been largely abandoned.
◆ Potts shunt: side-to-side anastomosis between the descending aorta and the left PA. Due to the high incidence of pulmonary hypertension this procedure has been largely abandoned.
◆ Glenn shunt: palliative procedure to increase pulmonary blood flow, and systemic oxygen saturation. A direct anastomosis is created between the superior vena cava and a PA. Modifications include the classic Glenn shunt with end-to-end anastomosis of the superior vena cava to the distal end of the divided right PA and the later modified bidirectional Glenn shunt (or partial cavopulmonary connection) with end-to-side anastomosis of the divided superior vena cava to the undivided PA. A Glenn procedure is nowadays commonly performed as part of a staged palliation for univentricular heart, culminating in a Fontan type palliation. In contrast to arterial shunts, a Glenn shunt avoids systemic ventricular volume overload and is therefore preferable. It requires, however, a low PAP.
Fontan type operations
The essence of Fontan type operations is to divert the systemic venous return to the PA, without the interposition of a sub-pulmonary ventricle. Modifications include:
◆ Classic Fontan: direct anastomosis between RA and PA.
◆ Lateral tunnel Fontan: IVC flow is directed by a baffle within the RA into the lower portion of the divided superior vena cava or the right atrial appendage, which is connected to the PA. The upper part of the superior vena cava is connected to the superior aspect of the PA as in the bidirectional Glenn procedure (
Fig. 22.21). Frequently, a fenestration is created to allow right-to-left shunting to reduce pressure in the systemic venous circuit, at the expense of systemic hypoxaemia. If haemodynamically suitable, the fenestration can be closed later by catheter intervention.◆ Extracardiac Fontan: IVC blood is directed to the PA via an extracardiac conduit. The superior vena cava is anastomosed to the PA as in the bidirectional Glenn shunt.
Echocardiographic assessment
Depending on thoracic situs, the heart may be located abnormally (e.g. right hemithorax) and this may affect acoustic windows and image views requiring CMR. It is recommended to first assess the cardiac anatomy systematically using a segmental approach (see earlier). The morphology and systolic function of the dominant ventricle should be assessed. The degree of AV valve regurgitation should be estimated. In addition, significant regurgitation or stenosis of the arterial valves should be assessed. The size and haemodynamic characteristics of VSDs should be estimated based on CD imaging and Doppler gradients.
In patients with PA banding, the gradient should be estimated to provide information on its efficacy or presence of pulmonary hypertension. Arterial shunt flow can be interrogated (supraclavicular for BT, parasternal for central shunts) but velocity measurements are unreliable for estimation of PAP.
In patients after Fontan palliation the patency of cavo-pulmonary pathways should be evaluated (although this frequently requires TOE and CMR) and the size of fenestrations should be assessed. In patients with classic Fontan the size of the RA may be considerable ( Fig. 22.22) and may lead to mechanical obstruction of pulmonary venous flow.
Echocardiography and treatment decision
Although in some patients with univentricular heart echocardiography may provide a comprehensive evaluation, the frequently limited image quality in adults and missing information on PAP and pulmonary vascular resistance make additional CMR or CT and invasive evaluation necessary for treatment decision.
Personal perspective
Due to advances in surgical and interventional treatment over the last six decades, the majority of children born with congenital heart disease now survive to adulthood. As a consequence, the number of adult patients with congenital heart disease is constantly increasing and currently exceeds the number of children with the condition. The majority of patients requires lifelong follow-up at specialized centres and echocardiography has emerged as the main modality for regular assessment of cardiac and valvular function in this setting. Although patients may require additional invasive and non-invasive investigations (such as CMR and CT), many clinical decisions can be based on the results of echocardiographic studies. With improving image quality, new modalities that assess ventricular function (such as strain and strain rate based on tissue Doppler and speckle-tracking imaging), and the advent of 3D echocardigraphy (offering new ways to assess valvular lesions and to measure ventricular volumes), the role of echocardiography in this evolving population is expected to increase further.
References
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Further reading
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Anderson RH, Baker EJ, Redington A, Rigby ML, Penny D, Wernovsky G. Paediatric Cardiology: Expert Consult – Online and Print, 3rd ed. Edinburgh: Churchill Livingstone, 2009.
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Baumgartner H. ESC guidelines for the management of grown-up congenital heart disease. The Task Force on the Management of Grown-up Congenital Heart Disease of the European Society of Cardiology (ESC). Eur Heart J 2010 Aug 27 [Epub ahead of print].
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