Non-obstructive Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most common genetic cardiomyopathy with a prevalence in the general population of 1:200. Among clinically recognized patients, HCM may be compatible with normal longevity. However, a subset of HCM patients remain at risk for several adverse disease related complications including sudden death, usually in the absence of symptoms, progressive heart failure symptoms and atrial fibrillation with risk of thromboembolic stroke. Initial evaluation of patients with HCM attempts to classify patients as either obstructive HCM or non-obstructive HCM.

At least one-third of HCM patients have the non-obstructive form of HCM with outflow gradient at rest or provoked of <30 mmHg. Diastolic dysfunction appears to be one of the most important determinants of heart failure symptoms in this group. The risk of developing progressive heart failure symptoms for non-obstructive HCM patients is 1.6%/year with approximately 30% of patients at any one point in time symptomatic with NYHA class II or III symptoms.

Therapeutic options are limited for this patient group. Verapamil or β-blockers are generally used for initial therapy for symptomatic patients and may improve exertional
dyspnea through reduction in heart rate and oxygen consumption and possibly due to direct effects on the microvasculature and diastolic filling.

For non-obstructive HCM patients with preserved systolic function (ejection fraction (EF) ≥50%) who develop symptoms refractory to drug therapy, heart transplant remains the only definitive long-term management option.

References: C. Semsarian et al. J Am Coll Cardiol, 65 (2015), pp. 1249-1254; Maron MS et al. Circulation. 2006 Nov 21;114(21):2232-9.