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Cardiomyopathy 

Cardiomyopathy
Chapter:
Cardiomyopathy
Author(s):

Giovanni Boffa

DOI:
10.1093/med/9780198759935.003.0018
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date: 14 October 2019

Cardiomyopathy

Disease of the heart muscle is referred to as cardiomyopathy. Broadly, there are three main types of functional impairment in cardiomyopathy, although often there is some overlap:

  • Hypertrophic cardiomyopathy (HCM).

  • Dilated cardiomyopathy (DCM).

  • Restrictive cardiomyopathy.

Hypertrophic cardiomyopathy

HCM is characterized by the presence of increased LV wall thickness that is not explained by loading conditions.1 The prevalence of HCM in different adult populations is reported in the range of 0.02–0.23%. In 40–60% of cases, HCM is an autosomal dominant trait caused by mutations in cardiac sarcomere protein genes; in 5–10% of cases, HCM is caused by other genetic disorders, and in 25–30% of cases, it is sporadic. The LV diastolic function is impaired to various degrees in the majority of patients, and about two-thirds of patients have resting or provocable LVOTO. HCM can be asymptomatic or cause a wide range of clinical manifestations: symptoms and signs of HF (secondary to diastolic dysfunction), angina (due to increased myocardial oxygen demand and microvascular dysfunction), arrhythmias, syncope, and SCD.

Management

Management of HCM is directed towards minimizing symptoms and reducing complications. Use of prophylactic drug therapy in asymptomatic or minimally symptomatic patients to prevent or delay disease progression remains unfounded.

  • β‎-blockers: reduce myocardial oxygen demand and improve LV filling via their negative chronotropic and inotropic effects. As a consequence, they may alleviate angina, as well as dyspnoea, and decrease LVOTO. Patients with symptomatic LVOTO should be treated initially with non-vasodilating β‎-blockers titrated to the maximum tolerated dose. Evidence-based data on the relative efficacy of individual β‎-blockers are not available.

There are no data to support the use of antiarrhythmics for the prevention of SCD in HCM. Use of β‎-blockers (and/or amiodarone) is today recommended only in patients with an ICD, who continue to have symptomatic ventricular arrhythmias or recurrent shocks despite optimal treatment. Use of β‎-blockers is recommended for controlling the ventricular rate in patients with paroxysmal, persistent, or permanent AF. Moreover, β‎-blockers are indicated, in addition to an ACEI, for the treatment of HF in patients with HF due to systolic compromise of LV function.

  • CCBs: verapamil or diltiazem can be used when β‎-blockers are contraindicated or ineffective. The benefit of CCBs is thought to derive from their ability to address the hypercontractile systolic function, while improving diastolic relaxation and filling of the LV. Caution is needed when administering these drugs, especially in those with high LV filling pressure, as their vasodilating property may exaggerate the LV outflow gradient. Dihydropyridine CCBs are not recommended for the treatment of LVOTO.

CCBs can be successfully used to treat angina and reduce the ventricular rate in AF.

  • Disopyramide: if β‎-blockers or CCBs alone are not sufficiently effective in reducing the outflow tract gradient, this class IA AAD may be added (titrated up to a maximum tolerated dose of usually 400–600mg/day). Disopyramide can abolish basal LV outflow pressure gradients and improve exercise tolerance.

  • Diuretics: can improve dyspnoea in patients with increased pulmonary capillary pressure due to severely compromised LV diastolic function, and their use is mandatory if signs of fluid retention are present.

  • Infective endocarditis prophylaxis is no longer recommended, even in patients with an outflow gradient.

The role of non-pharmacological treatment is of paramount importance in specific groups of patients. Septal reduction therapy (surgical myectomy or alcoholic ablation) is recommended in very symptomatic patients with an LV outflow gradient of 50mmHg, despite maximum tolerated medical therapy. ICD implantation is indicated in patients who have survived a cardiac arrest due to VT or VF, or who have spontaneous sustained VT causing syncope or haemodynamic compromise.

Cardiac transplantation may be indicated for end-stage patients who meet standard eligibility criteria. Ventricular assist devices can be used as a bridge to heart transplantation or destination therapy in selected patients.

Dilated cardiomyopathy

According to the position statement of the ESC Working Group on Myocardial and Pericardial Disease, DCM is defined by the presence of LV or biventricular dilatation and systolic dysfunction in the absence of abnormal loading conditions or CAD sufficient to cause global systolic impairment. The causes of DCM can be classified as genetic or non-genetic (drugs and toxins, myocarditis, peripartum DCM). Treatment of symptomatic patients should follow the therapeutic algorithm proposed by the 2016 ESC guidelines. The first-line treatment includes diuretics, ACE inhibition (or angiotensin receptor blockade), β‎-blockade, and aldosterone antagonism. The complex neprilysin inhibitor sacubitril/valsartan is recommended to replace ACEIs in patients who remain symptomatic despite optimal treatment. The If channel inhibitor ivabradine should be considered for patients in sinus rhythm and with a resting heart rate of >70bpm.

In symptomatic patients despite optimal medical treatment and with LVEF of <35%, implantation of ICD is recommended, with cardiac resynchronization function if the QRS duration is ≥150ms and in the presence of an LBBB QRS morphology.

LVAD implantation and heart transplantation can be the only solution in advanced HF patients.

Reference

1 Authors/Task Force members, Elliott PM, Anastasakis A, Borger MA, et al. 2014 ESC Guidelines on diagnosis and management of hypertrophic cardiomyopathy. The Task Force for the Diagnosis and Management of Hypertrophic Cardiomyopathy of the European Society of Cardiology (ESC). Eur Heart J 2014;35:2733–79.Find this resource:

Further reading

Pinto YM, Elliott PM, Arbustini E, et al. Proposal for a revised definition of dilated cardiomyopathy, hypokinetic non-dilated cardiomyopathy, and its implications for clinical practice: a position statement of the ESC working group on myocardial and pericardial diseases. Eur Heart J 2016;37:1850–8.Find this resource: