Introduction

Hypertrophic cardiomyopathy (HCM) is a genetic disease of cardiac muscle with a wide range of structural and functional abnormalities leading to symptoms of dyspnea, angina, and syncope. The many names that have been attributed to what is now known simply as hypertrophic cardiomyopathy reflect evolving understanding of the pathophysiology. Previous designations include functional aortic stenosis, muscular subaortic stenosis, idiopathic hypertrophic subaortic stenosis, and hypertrophic obstructive cardiomyopathy (HOCM). Currently, experts prefer a simpler nomenclature of hypertrophic cardiomyopathy with or without obstruction. Available therapies, both medical and surgical, have expanded over the last half-century, and HCM is now a treatable disease with favorable outcomes. Practice guidelines recommend initial medical management of symptomatic patients with obstructive HCM initially using nonvasodilating beta-blockers titrated to effectiveness or maximally tolerated doses.[1] In patients for whom beta-blockers are ineffective or not tolerated, substitution with non-dihydropyridine calcium channel blockers (eg, verapamil, diltiazem) is recommended, and for those who have persistent severe symptoms attributable to left ventricular outflow tract (LVOT) obstruction despite beta-blockers or non-dihydropyridine calcium channel blockers, either adding disopyramide in combination with 1 of the other drugs, or septal reduction therapy (SRT) by myectomy or alcohol septal ablation should be considered. A recently FDA-approved oral myosin inhibitor, mavacamten (Camzyos^®) has been shown in a randomized trial to reduce LVOT gradients and improve symptoms in patients who would otherwise be eligible for SRT.[2],[3] However, the long-term safety and effectiveness of mavacamten have not been established, and the use of the drug is costly and requires careful echocardiographic surveillance for systolic dysfunction.

As discussed below, transaortic septal myectomy is the preferred method of SRT for most symptomatic patients with obstructive HCM. Early surgical approaches aimed at alleviating left ventricular outflow tract (LVOT) obstruction were hampered by a lack of understanding of the anatomy and pathophysiology of obstructive HCM. With the advent of Doppler echocardiography and, more recently, cardiac MRI, surgeons can precisely assess the location and degree of obstruction, left ventricular size and function, and morphology and function of the mitral valve.