Obstructive hypertrophic cardiomyopathy: pathophysiology and diagnosis

Hypertrophic cardiomyopathy (HCM) is a genetic cardiac disorder characterized predominantly by left ventricular (LV) hypertrophy, frequently leading to dynamic obstruction of the left ventricular outflow tract (LVOT). Obstructive HCM is driven by structural abnormalities including asymmetric septal hypertrophy, systolic anterior motion of often elongated mitral valve leaflets, and alterations in the mitral sub-valvular apparatus such as displaced or hypertrophied papillary muscles. Pathophysiological mechanisms underlying HCM include hypercontractility due to increased actin-myosin cross bridges, myocyte hypertrophy and disarray, interstitial fibrosis, and coronary microvascular dysfunction-which contribute variably to disease expression, impaired myocardial relaxation, ischemia, fibrosis, and arrhythmogenesis. Diagnosis relies on integrating clinical presentation, physical examination, electrocardiographic features, genetic testing, and advanced imaging techniques. Transthoracic echocardiography remains the primary diagnostic and monitoring tool, accurately assessing patterns of hypertrophy, dynamic LVOT gradients, mitral valve abnormalities, and ventricular function, including strain imaging for early functional impairment. Cardiac magnetic resonance imaging complements echocardiography, providing superior anatomical delineation, precise quantification of LV mass, detection of apical and distal-dominant forms, identification of fibrosis via late gadolinium enhancement, and detailed tissue characterization. This review emphasizes the complex interplay of genetic, structural, and functional elements in obstructive HCM, underscoring the importance of comprehensive evaluation to facilitate individualized and effective therapeutic decisions.