Key Points:

1. HCM — defined as left ventricular (LV) hypertrophy (maximal wall thickness, 15 mm) without LV dilatation and without cardiac or systemic conditions that can explain the extent of the hypertrophy — is a common genetic cardiovascular disease, affecting approximately 600,000 individuals in the U.S. (0.2% of the population).

2. The prognosis of HCM is highly variable; many affected individuals have a normal life expectancy. Three distinct (but potentially interrelated) sequelae are:

SCD 

Heart failure due to dynamic LV outflow obstruction and associated mitral regurgitation 

Atrial fibrillation (AF) and related thromboembolic complications 

3. Clinical screening, including electrocardiography and echocardiography, is recommended for all first-degree relatives of patients with HCM (Class I).

4. Genetic testing is not recommended (Class III) unless the index patient has a definitive pathogenic mutation.

5. The value of pharmacotherapy aimed at HCM is unclear (Class IIb). Asymptomatic patients should not be considered for septal reduction therapy, regardless of the severity of LV outflow tract (LVOT) obstruction (Class III).

6. Beta-blockers, titrated to a resting heart rate of 60 to 65 beats per minute, are recommended for treatment of angina or dyspnea in adults with obstructive or nonobstructive HCM. Verapamil should be considered in patients who do not respond or who have contraindications to beta-blockers (Class I).

7. Nifedipine or other dihydropyridine calcium-channel blockers; digitalis in the absence of AF; disopyramide without concomitant beta blockade; and positive inotropes are all potentially harmful to patients with HCM (Class III).

8. Septal reduction therapy should be considered only in patients with severe, drug-refractory symptoms and a resting or provoked LVOT gradient of at least 50 mm Hg (Class I). Surgical septal myectomy is generally preferred when septal reduction is appropriate; alcohol septal ablation can be considered in patients with serious comorbidities or a strong aversion to surgery (Class IIa).

9. ICD therapy is recommended in patients with prior cardiac arrest or sustained ventricular tachycardia (VT) (Class I); in those with a history of SCD in a first-degree relative, marked LV hypertrophy, or recent unexplained syncope (Class IIa); and in those with nonsustained VT or an abnormal blood-pressure response to exercise (Class IIa or IIb, depending upon the presence of other risk modifiers, including marked LVOT obstruction).

10. Patients with HCM should not participate in intense competitive sports (e.g., basketball, soccer, or tennis), whether or not they have LVOT obstruction, prior septal reduction therapy, or an ICD (Class III).

Comment: The writing group appropriately acknowledges that the evidence is limited regarding the screening, prognosis, and therapy for this heterogeneous condition. Indeed, not a single Class I recommendation is assigned a level of evidence of A. Nevertheless, the guidelines provide comprehensive consensus recommendations for the diagnosis and treatment of HCM as well as for the screening of patients' relatives. Given the prevalence of HCM in the community, the authors' call for a more-robust evidence base is compelling.

— Frederick A. Masoudi, MD, MSPH, FACC, FAHA

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