Hypertrophic Obstructive Cardiomyopathy (HOCM) is a genetic cardiac disorder characterized by abnormal thickening (hypertrophy) of the heart muscle, predominantly involving the interventricular septum, which results in obstruction of blood flow from the left ventricle to the aorta. It represents a subset of hypertrophic cardiomyopathy (HCM) and is a leading cause of sudden cardiac death in young adults and athletes when undiagnosed.

HOCM is most commonly caused by autosomal dominant mutations in genes encoding sarcomeric proteins, such as beta-myosin heavy chain and myosin-binding protein C. These mutations lead to myocyte disarray, myocardial fibrosis, and impaired ventricular relaxation. The hallmark feature of HOCM is dynamic left ventricular outflow tract (LVOT) obstruction, which worsens during exertion, dehydration, or increased contractility.

The obstruction is often exacerbated by systolic anterior motion (SAM) of the mitral valve, where the mitral leaflet is drawn toward the hypertrophied septum during systole, further narrowing the LVOT and causing mitral regurgitation. This results in elevated intracardiac pressures, reduced cardiac output, and myocardial ischemia despite normal coronary arteries.

Clinical presentation varies widely. Some patients remain asymptomatic, while others develop exertional dyspnea, chest pain, palpitations, dizziness, syncope, or near-syncope. Symptoms often worsen with physical activity due to increased obstruction. Importantly, HOCM may present with sudden cardiac arrest as the first manifestation, particularly in young individuals.

Physical examination may reveal a harsh systolic murmur that increases with maneuvers that reduce preload (e.g., standing or Valsalva maneuver). Diagnosis is primarily established through transthoracic echocardiography, which demonstrates asymmetric septal hypertrophy, LVOT gradient, SAM of the mitral valve, and diastolic dysfunction. Cardiac MRI provides further characterization of myocardial fibrosis and risk stratification. ECG often shows left ventricular hypertrophy, repolarization abnormalities, or arrhythmias.

Risk stratification is central to HOCM management, focusing on predictors of sudden cardiac death such as family history of sudden death, unexplained syncope, severe hypertrophy, ventricular arrhythmias, and extensive myocardial fibrosis.

Management aims to reduce LVOT obstruction, control symptoms, and prevent complications. First-line therapy includes negative inotropic agents such as beta-blockers or non-dihydropyridine calcium channel blockers to reduce heart rate and contractility. In refractory cases, disopyramide may be added.

Patients with severe, drug-refractory symptoms and significant LVOT gradients may require septal reduction therapy, either through surgical septal myectomy or alcohol septal ablation in selected candidates. Implantable cardioverter-defibrillators (ICDs) are recommended in high-risk patients for sudden cardiac death prevention.

With specialized care, early diagnosis, and individualized management, many patients with HOCM can achieve symptom control and long-term survival with preserved quality of life.