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Congenital heart disease in the adult 

Congenital heart disease in the adult

Chapter:
Congenital heart disease in the adult
Author(s):

S. A. Thorne

DOI:
10.1093/med/9780199204854.003.1612_update_002

Update:

March 2014 – this chapter has been extensively revised, with new figures to explain and describe the classification of congenital heart disease.

Updated on 29 Oct 2015. The previous version of this content can be found here.
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date: 25 March 2017

Adults with congenital heart disease are a growing population, and now outnumber children with congenital heart disease in the United Kingdom. Many patients with repaired hearts can now, with specialist care, expect to live a normal or near normal lifespan. Other survivors have complex, surgically altered hearts and circulations that reflect the surgical and interventional practices of the preceding two decades. Their long-term outlook is unknown and they remain at lifelong risk of complications that may require further intervention. The organization of services to provide specialist care is key to their long-term survival.

The language of congenital heart disease

The classification and description of complex congenital heart disease can appear intimidating, but should be easily understood by using a simple physiological approach that takes into account whether a condition is cyanotic or acyanotic, whether there is a shunt, and the implications of the morphology for pulmonary blood flow.

The description of the congenitally malformed heart is aided by a sequential segmental analysis of the relationship of the three cardiac segments, which makes it possible to understand and describe how a complex heart is connected. The three segments to be considered are: (1) the atriums; (2) the ventricles; (3) the great vessels. The next step is to describe how each segment connects to the others.

Cyanosis and pulmonary hypertension

Cyanosis occurs as a result of a right to left shunt, with its natural history determined by the pulmonary blood flow. If pulmonary blood flow is limited (e.g. by pulmonary stenosis in the presence of a large ventricular septal defect), then pulmonary blood flow and arterial oxygen will be low, as will pulmonary artery pressure. Cyanotic patients with low or normal pulmonary artery pressure are usually amenable to surgical repair that abolishes the cyanosis. By contrast, if the pulmonary circulation is unprotected (e.g. if the defect includes a large ventricular septal defect and no pulmonary stenosis), then pulmonary blood flow will be high and at high pressure, pulmonary vascular remodelling will occur, and—without intervention—pulmonary vascular disease will eventually develop (pulmonary arterial hypertension; the Eisenmenger syndrome). Once pulmonary vascular disease is established, it is not possible to repair the defect and abolish the right-to-left shunt.

The right ventricle

Preservation of ventricular function is fundamental in allowing long-term survival with a good quality of life. The right ventricle is a key factor in the long-term outcome of many congenital cardiac conditions. It may fail as a result of either long-standing pressure or volume overload. (1) Pressure loading—this occurs in patients in whom the right ventricle supports the systemic circulation, such as those with congenitally corrected transposition of the great arteries, and in those who underwent interatrial repair (Mustard or Senning operation) of simple transposition of the great arteries. The right ventricle is hypertrophied, and ultimately fails, with tricuspid regurgitation secondary to annular dilatation hastening the decline. (2) Volume loading—this commonly occurs as a result of pulmonary regurgitation secondary to pulmonary valvotomy or repair of tetralogy of Fallot in early life. There may be no audible murmur because there are often only remnants of pulmonary valve tissue, such that the regurgitant flow is laminar. Partly because of the lack of physical signs, and partly because pulmonary regurgitation is usually tolerated for many years before the right ventricle begins to fail, patients may present very late with a very dilated and impaired ventricle. Long-standing large atrial septal defects produce similar right ventricular volume loading effects. The right ventricle may be inherently abnormal, as in Ebstein’s anomaly where a combination of a functionally small ventricle and volume loading from tricuspid regurgitation may cause the right ventricle to fail.

The Fontan circulation

Hearts which have only one functional ventricle present a particularly difficult challenge. Patients are cyanosed, and only a few will reach adulthood if left unoperated. The ultimate aim for patients with only one functional ventricle is a Fontan circulation: a palliative approach that reduces ventricular volume loading and abolishes cyanosis. It is critically dependent on a low pulmonary vascular resistance, hence early control of pulmonary blood flow is paramount. If pulmonary blood flow is too high, it is controlled by placing a pulmonary artery band: i.e. by the creation of iatrogenic, protective pulmonary stenosis. If pulmonary blood flow is too low, the infant will not thrive, and pulmonary blood supply is augmented by means of a systemic to pulmonary artery shunt. There are many variations of the Fontan operation, but all involve the separation of pulmonary and systemic circulations by using the single ventricle to support the systemic circulation and by connecting the systemic veins directly (or via the right atrium) to the pulmonary artery. There is thus no ‘pump’ in the pulmonary circulation, so although cyanosis is abolished, the Fontan circulation is one of a chronic low-output state. Thus, although the Fontan approach enables most patients with a single ventricle to reach adulthood, they have a fragile circulation and will develop a range of complications. They are particularly at risk if they have a tachyarrhythmia or acute noncardiac illness, since they tolerate such insults poorly and are dependent on their medical teams’ understanding of their circulation to ensure good hydration, avoidance of vasodilatation, and rapid restoration of sinus rhythm.

Tachyarrhythmia

Tachyarrhythmias are a major cause of sudden death in patients with congenital heart disease, with scar-related atrial tachyarrythmias being common in those who have had previous cardiac surgery, and probably a commoner cause of death than ventricular arrhythmias. Atrial tachyarrhymias are the reason that patients who underwent interatrial repair (Mustard or Senning operations) of transposition of the great arteries are the congenital cardiac group with the highest incidence of sudden death. Their surgically created atrial ‘baffles’ mean that atrial function is abnormal, and ventricular filling is impaired, particularly at high heart rates. Atrial flutter is common post Mustard or Senning, and patients are usually able to conduct 1:1 at a rate of 300 bpm, resulting in cardiovascular collapse. Correct management is rapid restoration of sinus rhythm, followed by flutter ablation. Patients with a Fontan circulation are similarly vulnerable to interatrial re-entry tachyarrythmias. Ventricular and atrial tachycardias may both occur in most survivors of complex congenital heart disease, particularly after repair of tetralogy of Fallot. If ablation is not successful, consideration should be given to an internal cardioverter defibrillator.

Pregnancy and contraception

Most women with congenital heart disease wish to consider pregnancy. For most this can be undertaken with only a small increased risk, but for some pregnancy carries a significant risk of complication, long-term morbidity, and death. Outcomes can be optimized by preconception counselling and specialist joint cardiac and obstetric care. Access to safe and effective contraception is important to allow patients to avoid potentially high risk pregnancies. Oestrogen-containing preparations are not suitable for those at risk of intracardiac thrombus or who have a right-to-left shunt; long-acting progestogen-only methods offer safe and effective alternatives

Heart failure and end-of-life care

As the population of adults with congenital heart disease ages, so the number developing heart failure increases. Conventional heart failure drugs have not been shown to have much benefit in this situation, and there is a lack of clear guidance as to who will benefit from interventions such as cardiac resynchronization therapy. Cardiac transplantation is associated with a worse early mortality than acquired heart disease, but the long-term outcome is as good. Transplantation is limited both by suitability of the recipient with a complex, surgically modified heart, and by donor availability. Services caring for patients need to develop a robust end-of-life pathway that focuses on symptoms and quality of life, and runs in parallel with other therapies.

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