Forward Dynamics: Modern Insights into Mitral Systolic Anterior Motion

Systolic anterior motion (SAM) of the mitral valve can occur either in association with or in the absence of hypertrophic obstructive cardiomyopathy (HOCM). SAM induces dynamic left ventricular outflow tract obstruction (LVOTO) and, in the majority of cases, is associated with a substantial degree of mitral regurgitation (MR) that significantly impacts patient morbidity and mortality. This narrative review explores the contemporary understanding of the pathophysiology, diagnosis, and management of SAM, focusing particularly on surgical strategies and the novel therapeutic class of cardiac myosin inhibitors. Extended septal myectomy remains the gold-standard treatment for HOCM-related SAM, yielding superior long-term outcomes compared to alcohol septal ablation (ASA). Advanced imaging modalities, including three-dimensional transesophageal echocardiography (3D-TEE), enable precise pre-operative characterization of the mitral valve apparatus. Some patients may benefit from septal reduction strategies while concomitant mitral valve interventions are generally reserved for highly selected cases with intrinsic valve pathology or persistent residual SAM, thereby avoiding unnecessary valvular manipulation and its potential hemodynamic risks. Mavacamten, a selective cardiac myosin inhibitor, represents an important advance in pharmacological management, achieving a mean LVOT gradient reduction of 37.2 mmHg in symptomatic patients. Furthermore, data from the MARVEL registry confirm the real-world clinical efficacy of mavacamten in obstructive hypertrophic cardiomyopathy, with 86% of patients successfully down-staged to NYHA functional class I–II. Although ASA serves as a viable alternative to surgery, it entails a higher risk of conduction abnormalities requiring permanent pacemaker implantation and subsequent re-intervention. Beyond classical hypertrophic SAM, this review addresses the diagnosis and management of post-mitral repair complications and non-hypertrophic variants. Optimal management and risk stratification remain an evolving field requiring a multidisciplinary Heart Team approach, leverage of advanced imaging, and adoption of novel medical therapies. Interventional strategies must be carefully tailored to maximize the efficacy-to-safety profile on an individualized patient basis.