Hypertrophic cardiomyopathy is a common genetic heart disease characterized by left ventricular hypertrophy in the absence of a valvular, systemic, or metabolic cause. In addition to its hemodynamic consequences, hypertrophic cardiomyopathy predisposes to arrhythmias, including bradyarrhythmias, atrial and ventricular tachyarrhythmias, and sudden death, and, in some, end-stage dilated or restrictive 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 pharmacotherapy, and measures for heart failure.
Hypertrophic cardiomyopathy (HCM) in general is reviewed elsewhere in The Manual. This topic focuses on its arrhythmogenic features. (See also Overview of Arrhythmogenic Cardiomyopathies and Overview of Arrhythmias.)
Hypertrophic cardiomyopathy (HCM) is a genetic disorder of the sarcomere characterized by ventricular hypertrophy with diastolic dysfunction in the absence of increased afterload (eg, not due to valvular aortic stenosis, coarctation of the aorta, systemic hypertension).
Inherited hypertrophic cardiomyopathy is a common (1/200 to 1/500) cardiac disorder (1, 2), usually autosomal dominant with variable penetrance, that affects as many as 20 million people worldwide (2). The underlying etiology is one of more than 2000 reported mutations in multiple genes encoding myofilament proteins of the sarcomere. Genetic testing is positive in 30 to 60% of patients with hypertrophic cardiomyopathy (3).
The phenotype is very diverse but typically is characterized by left ventricular hypertrophy often accompanied by left ventricular outflow tract obstruction, atrial tachyarrhythmias, ventricular tachyarrhythmias, end-stage dilated or restrictive cardiomyopathy, or sudden death. (4). Although the left ventricular hypertrophy is typically asymmetrical, with the anterior septum and anterior free wall hypertrophied much more than is the posterior wall, subtypes with concentric left ventricular hypertrophy or isolated left ventricular apical hypertrophy are also 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.)
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 (2). Atrial fibrillation is also very frequent (prevalence approximately 20%) and may be particularly poorly tolerated secondary to aggravation of ventricular diastolic dysfunction by rapid ventricular rates (2).
Symptoms and signs, when present, often are exertional and include dyspnea, chest pain (usually resembling typical angina), palpitations, and syncope. Syncope may be caused by arrhythmia or outflow tract obstruction.
General references
1. McKenna WJ, Judge DP. Epidemiology of the inherited cardiomyopathies. Nat Rev Cardiol. 2021;18(1):22-36. doi:10.1038/s41569-020-0428-2
2. Maron BJ. Clinical Course and Management of Hypertrophic Cardiomyopathy. N Engl J Med. 2018;379(7):655-668. doi:10.1056/NEJMra1710575
3. Girolami F, Gozzini A, Pálinkás ED, et al. Genetic Testing and Counselling in Hypertrophic Cardiomyopathy: Frequently Asked Questions. J Clin Med. 2023;12(7):2489. doi:10.3390/jcm12072489
4. Ottaviani A, Mansour D, Molinari LV, et al. Revisiting Diagnosis and Treatment of Hypertrophic Cardiomyopathy: Current Practice and Novel Perspectives. J Clin Med. 2023;12(17):5710. doi: 10.3390/jcm12175710.
Diagnosis of Hypertrophic Cardiomyopathy Arrhythmias
History and physical examination including a 3-generation family history
Echocardiography, and often cardiac MRI
ECG, ambulatory rhythm monitoring, exercise testing
Genetic testing
Screening of first-degree relatives
The diagnosis of hypertrophic cardiomyopathy is suggested by an ECG showing left ventricular hypertrophy and by characteristic clinical findings on physical examination. A 3-generation family history should be obtained (1).
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 performed if required to establish the diagnosis or to quantify left ventricular scarring when needed to further assess risk of sudden cardiac death. Left heart catheterization may also be performed to clarify the presence of degree of LV outflow tract obstruction.
The diagnosis may also be made during periodic surveillance of asymptomatic family members of individuals with hypertrophic cardiomyopathy, or during screening of family members following the sudden, unexpected death of a relative. Family members of individuals with hypertrophic cardiomyopathy should have clinical evaluation (ie, to detect symptoms suggestive of arrhythmia and/or heart failure), ECG, and echocardiography. The timing and frequency of family member surveillance is:
For children and adolescents in families with an identified causative gene mutation or with early-onset disease: Beginning at the time of the family member's diagnosis, and then every 1 to 2 years
For other children and adolescents: Beginning no later than puberty, and then every 2 to 3 years
For adults: Beginning at the time of the family member's diagnosis, and then every 3 to 5 years
Although genetic testing has a relatively low sensitivity, it is still recommended to allow cascade screening of family members. Nevertheless, whether genetic findings predict future life-threatening arrhythmias remains unclear. Genotype-positive, phenotype-negative individuals are not considered to have hypertrophic cardiomyopathy but require careful periodic surveillance.
The diagnosis of hypertrophic cardiomyopathy includes considering, and excluding, other disorders that produce similar cardiac findings (phenocopies), including hypertensive heart disease, athlete's heart, cardiac amyloid, and Anderson-Fabry disease (1, 2).
Initial arrhythmia evaluation includes ECG, ambulatory cardiac rhythm monitoring (24- to 48-hour monitors for most patients, longer-term monitors for those at high risk of atrial fibrillation) and exercise testing (1). Subsequent regular (every 1 to 2 years) clinical follow-up also includes ECG, ambulatory rhythm monitoring, and exercise testing, in addition to echocardiography.
Diagnosis references
1. Ommen SR, Ho CY, Asif IM, et al. 2024 AHA/ACC/AMSSM/HRS/PACES/SCMR Guideline for the Management of Hypertrophic Cardiomyopathy: A Report of the American Heart Association/American College of Cardiology Joint Committee on Clinical Practice Guidelines. Circulation. 2024;149(23):e1239-e1311. doi:10.1161/CIR.0000000000001250
2. Ottaviani A, Mansour D, Molinari LV, et al. Revisiting Diagnosis and Treatment of Hypertrophic Cardiomyopathy: Current Practice and Novel Perspectives. J Clin Med. 2023;12(17):5710. doi: 10.3390/jcm12175710.
Treatment of Hypertrophic Cardiomyopathy Arrhythmias
Moderation of physical activity
For atrial fibrillation, antiarrhythmic pharmacotherapy 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, septal alcohol ablation, or cardiac myosin inhibitor therapy)
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). Given the health benefits of exercise, universal restriction is not recommended, and mild to moderate recreational exercise is generally encouraged. Some individuals may reasonably pursue competitive sports or vigorous exercise after careful discussion and consideration of risks and benefits (2, 3).
Standard measures for treatment of hypertrophic cardiomyopathy include beta-blockers and heart rate-limiting calcium channel blockers. These may be beneficial not only for rate and rhythm control, but also to relieve left ventricular outflow tract obstruction or anginal symptoms (1). On occasion, right ventricular pacing is used to treat outflow tract obstruction by purposefully inducing interventricular dyssynchrony. Cardiac resynchronization pacing therapy may be required in patients who have progressed to a dilated cardiomyopathy.
For atrial tachyarrhythmias, standard treatment is used: rate-control with negative dromotropic medications (usually a beta-blocker), rhythm control (usually with amiodarone), and thromboembolic risk reduction (with a direct acting oral anticoagulant as first-line option over warfarin). Patients with hypertrophic cardiomyopathy and atrial fibrillation should receive anticoagulant therapy regardless of their CHA2DS2-VASc score (1).
For ventricular arrhythmias, prevention of sudden death is with an ICD. ICDs are generally recommended for patients with cardiomyopathy and left ventricular ejection fraction of ≤ 35% (4). For patients with hypertrophic cardiomyopathy, the decision to place and ICD should follow a shared decision-making model with careful consideration of risks and benefits (1).
ICD placement in adults with hypertrophic cardiomyopathy is recommended for:
Documented cardiac arrest or sustained ventricular tachycardia
Progression to dilated cardiomyopathy with left ventricular ejection fraction < 35% (based on general heart failure recommendations)
ICD placement in adults with hypertrophic cardiomyopathy is reasonable for:
Sudden death likely due to hypertrophic cardiomyopathy in a first-degree or close relative ≤ 50 years of age
Maximal left ventricular thickness ≥ 3.0 cm
Syncope due to arrhythmia, not neurocardiogenic/vasovagal or related to left ventricular outflow tract obstruction
Left ventricular apical aneurysm with transmural fibrosis/late gadolinium enhancement on MRI
Left ventricular systolic function < 50%
ICD placement in adults with hypertrophic cardiomyopathy may be considered for:
Extensive late gadolinium enhancement on MRI
Nonsustained ventricular tachycardia
This echocardiogram shows severe septal thickening in hypertrophic cardiomyopathy. The dots on either side of the scan are 1 cm apart. Thus, the ventricular septal (VS) thickness is more than 4 cm compared to the posterior left ventricle wall (PW) thickness of 2 cm (asymmetric septal hypertrophy). Because the septal thickness is > 3 cm, this is a reasonable indication for ICD implantation for prevention of sudden cardiac death regardless of other findings.
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For pediatric patients, recommendations for ICD placement are similar but the risk/benefit discussion should include the higher rate of ICD complications, particularly inappropriate shocks, in children (1). (see table ).
European guidelines specifically recommend using the Hypertrophic Cardiomyopathy Risk-Sudden Cardiac Death calculator (qxmd.com/calculate/calculator_303/hcm-risk-scd) to calculate the 5-year risk of sudden cardiac death and guide ICD placement in patients ≥ 16 years old, with consideration of other risk factors and shared decision-making (5).
Antiarrhythmic medications (usually amiodarone, with dofetilide, mexiletine, or sotalol as other recommended options) are used to control frequently recurrent ventricular tachyarrhythmias leading to frequent ICD interventions, particularly ICD shocks (1). Transcatheter ablation of the arrhythmogenic substrate may also be used (1).
Outflow tract obstruction may be helped by beta-blockers and sometimes septal reduction therapy (surgical or by alcohol ablation) or cardiac myosin adenosine triphosphatase inhibition with mavacamten or aficamten (6).
Treatment references
1. Ommen SR, Ho CY, Asif IM, et al. 2024 AHA/ACC/AMSSM/HRS/PACES/SCMR Guideline for the Management of Hypertrophic Cardiomyopathy: A Report of the American Heart Association/American College of Cardiology Joint Committee on Clinical Practice Guidelines. Circulation. 2024;149(23):e1239-e1311. doi:10.1161/CIR.0000000000001250
2. Kim JH, Baggish AL, Levine BD, et al. Clinical Considerations for Competitive Sports Participation for Athletes With Cardiovascular Abnormalities: A Scientific Statement From the American Heart Association and American College of Cardiology. J Am Coll Cardiol. 2025;85(10):1059-1108. doi:10.1016/j.jacc.2024.12.025
3. Lampert R, Ackerman MJ, Marino BS, et al. Vigorous Exercise in Patients With Hypertrophic Cardiomyopathy. JAMA Cardiol. 2023;8(6):595-605. doi:10.1001/jamacardio.2023.1042
4. Al-Khatib SM, Stevenson WG, Ackerman MJ, et al. 2017 AHA/ACC/HRS Guideline for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society. Circulation. 2018;138(13):e272-e391. doi:10.1161/CIR.0000000000000549
5. Arbelo E, Protonotarios A, Gimeno JR, et al. 2023 ESC Guidelines for the management of cardiomyopathies. Eur Heart J. 2023;44(37):3503-3626. doi:10.1093/eurheartj/ehad194
6. Lee MMY, Goldie FC, Henderson AD, Masri A, Olivotto I, Coats CJ. Efficacy and safety of cardiac myosin inhibitors in obstructive hypertrophic cardiomyopathy: Systematic review and comprehensive frequentist and Bayesian meta-analyses of Phase 3 randomized controlled trials. Prog Cardiovasc Dis. 2026;94:16-26. doi:10.1016/j.pcad.2025.10.002
Key Points
Hypertrophic cardiomyopathy is arrhythmogenic, predisposing to atrial and ventricular tachyarrhythmias and sudden death.
Diagnosis is by genetic testing, ECG, echocardiography, and often cardiac MRI.
Atrial tachyarrhythmias are treated with medications and ventricular dysrhythmias with an implantable cardioverter-defibrillator (ICD).
Exercise recommendations are based on thorough evaluation and shared decision-making.
Drug Information for the Topic
