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Hypertrophic Cardiomyopathy Arrhythmias

By

L. Brent Mitchell

, MD, Libin Cardiovascular Institute of Alberta, University of Calgary

Last review/revision Jan 2023
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Any hypertrophic cardiomyopathy can produce cardiac and systemic factors that predispose to arrhythmias, including bradyarrhythmias, atrial and ventricular tachyarrhythmias, and sudden death, and eventually end-stage dilated cardiomyopathy. Arrhythmias may cause palpitations, syncope, and/or cardiac arrest. Diagnosis includes ECG, cardiac imaging, and genetic testing. Treatment is usually an implantable cardioverter-defibrillator (ICD), antiarrhythmic drug therapy, and standard measures for heart failure.

Inherited hypertrophic cardiomyopathy is a common (1/500) cardiac disorder, usually autosomal dominant with variable penetrance. The underlying etiology is one of more than 1500 reported mutations in genes encoding myofilament proteins of the sarcomere, but genetic testing is negative in approximately 2/3 of patients with hypertrophic cardiomyopathy.

The phenotype is very diverse but typically is characterized by left ventricular hypertrophy (LVH) often accompanied by left ventricular outflow tract obstruction, atrial tachyarrhythmias, ventricular tachyarrhythmias, sudden death, and end-stage dilated cardiomyopathy. The LVH is typically asymmetrical, in which the anterior septum and anterior free wall are hypertrophied much more than is the posterior wall. Nevertheless, subtypes with concentric left ventricular hypertrophy or isolated left ventricular apical hypertrophy are recognized. Cardiac function is compromised because hypertrophy results in a stiff, noncompliant left ventricle that resists diastolic filling, elevating end-diastolic pressure and thus increasing pulmonary venous pressure. As resistance to filling increases, cardiac output decreases, an effect worsened by any outflow tract gradient present. Because tachycardia allows less time for filling, symptoms tend to appear (or worsen) mainly during exercise or tachyarrhythmias. (See also Heart failure with preserved ejection fraction Heart failure with preserved ejection fraction (HFpEF) Heart failure (HF) is a syndrome of ventricular dysfunction. Left ventricular (LV) failure causes shortness of breath and fatigue, and right ventricular (RV) failure causes peripheral and abdominal... read more Heart failure with preserved ejection fraction (HFpEF) .)

In regards to arrhythmias, the hypertrophy is associated with myofibril disarray, microvasculopathy, microvascular insufficiency, ischemia, and myocardial scarring, all of which predispose to ventricular tachyarrhythmias and sudden death. Atrial fibrillation Atrial Fibrillation Atrial fibrillation is a rapid, irregularly irregular atrial rhythm. Symptoms include palpitations and sometimes weakness, effort intolerance, dyspnea, and presyncope. Atrial thrombi may form... read more is also very frequent and may be particularly poorly tolerated secondary to aggravation of ventricular diastolic dysfunction by rapid ventricular rates.

Symptoms and signs often are exertional and include dyspnea, chest pain (usually resembling typical angina), palpitations, and syncope. The syncope may be caused by arrhythmia or outflow tract obstruction.

Diagnosis of Hypertrophic Cardiomyopathy Arrhythmias

  • ECG, echocardiography, and often cardiac MRI

  • Often ambulatory cardiac monitoring

  • Rarely, genetic testing

  • Screening of first-degree family members

The diagnosis of hypertrophic cardiomyopathy is suggested by an ECG showing left ventricular hypertrophy and by characteristic clinical findings on physical examination. Diagnosis is confirmed by cardiac imaging, usually transthoracic echocardiography, showing left ventricular hypertrophy, particularly asymmetrical left ventricular hypertrophy. A cardiac magnetic resonance examination using gadolinium is then done to quantify left ventricular scarring, which helps assess risk of sudden cardiac death.

Arrhythmia evaluation usually includes ambulatory cardiac rhythm monitoring and exercise testing.

Patients also should have regular (eg, annual) clinical follow-ups, including ECG, echocardiography, ambulatory cardiac rhythm monitoring, and exercise testing.

Because of its low sensitivity, genetic testing is not recommended for patients but may be used to screen family members if a specific mutation in the family is known or for patients with genetic links to a geographic region where a local mutation is known to be present. Family members also should have clinical evaluation (ie, to detect symptoms suggestive of arrhythmia and/or heart failure), ECG, and echocardiography.

Treatment of Hypertrophic Cardiomyopathy Arrhythmias

  • Moderation of physical activity

  • For atrial fibrillation, antiarrhythmic drug therapy and anticoagulation for stroke prevention

  • For ventricular arrhythmias, often an implantable cardioverter-defibrillator (ICD)

  • Heart failure therapy (including transplantation) as required

  • Outflow tract obstruction therapy as required (usually a beta-blocker but sometimes septal myomectomy or alcohol ablation)

Patients with hypertrophic cardiomyopathy have typically been advised to avoid athletic exertion because such activities foster life-threatening arrhythmias and may hasten disease progression. However, current guidelines recommend that patients may continue to pursue recreational athletic activity after a comprehensive evaluation and shared discussion with an expert specialist in hypertrophic cardiomyopathy of potential risk (and the understanding that individual exercise risk cannot be precisely predicted— 1 Treatment reference Any hypertrophic cardiomyopathy can produce cardiac and systemic factors that predispose to arrhythmias, including bradyarrhythmias, atrial and ventricular tachyarrhythmias, and sudden death... read more ).

For atrial tachyarrhythmias, standard treatment is used: rate-control with negative dromotropic drugs (usually a beta-blocker), rhythm control (usually with amiodarone), and thromboembolic risk reduction (usually with warfarin or a direct acting oral anticoagulant).

For ventricular arrhythmias, prevention of sudden death is with an ICD, which is recommended for patients with dilated cardiomyopathy and left ventricular ejection fraction of 35% or less and for patients with sustained ventricular tachycardia/ventricular fibrillation or resuscitated cardiac arrest. Because of the higher risk of sudden death in patients with hypertrophic cardiomyopathy, current guidelines also recommend an ICD for patients with other specific combinations of risk factors (see table ). Antiarrhythmic drugs, usually amiodarone, are used to control frequently recurrent ventricular tachyarrhythmias leading to frequent ICD interventions, particularly ICD shocks.

Standard measures for treatment of hypertrophic cardiomyopathy Treatment Hypertrophic cardiomyopathy is a congenital or acquired disorder characterized by marked ventricular hypertrophy with diastolic dysfunction (eg, due to valvular aortic stenosis, coarctation... read more Treatment include beta-blockers and heart rate-limiting calcium channel blockers. On occasion, right ventricular pacing is used to treat outflow tract obstruction by purposefully inducing interventricular dyssynchrony. Cardiac resynchronization pacing therapy Cardiac Resynchronization Therapy (CRT) The need for treatment of arrhythmias depends on the symptoms and the seriousness of the arrhythmia. Treatment is directed at causes. If necessary, direct antiarrhythmic therapy, including antiarrhythmic... read more may be required in patients who have progressed to a dilated cardiomyopathy. Outflow tract obstruction also may be helped by beta-blockers and sometimes septal reduction therapy (surgical or by alcohol ablation).

Treatment reference

  • 1. Ommen SR, Mital S, Burke MA, et al: 2020 AHA/ACC Guideline for the Diagnosis and Treatment of Patients With Hypertrophic Cardiomyopathy A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines. Circulation 142(25):e533–e557, 2020. doi: 10.1161/CIR.0000000000000937

Key Points

  • Hypertrophic cardiomyopathy is arrhythmogenic, predisposing to atrial and/or ventricular tachyarrhythmias and sudden death.

  • Cases may be inherited or acquired.

  • Diagnosis is by ECG, echocardiography, and often cardiac MRI.

  • Atrial tachyarrhythmias are treated with drugs and ventricular dysrhythmias with an implantable cardioverter-defibrillator (ICD).

  • Exercise is no longer strictly prohibited provided appropriate evaluation and shared decision-making are done.

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