Systolic Anterior Motion (SAM) Complicating Mitral Valve Repair: Current Concepts of Intraoperative and Postoperative Management.

Mitral valve repair is the gold standard for treatment of degenerative mitral regurgitation, such as that caused by leaflet prolapse, flail or annular dilatation. A variety of surgical techniques allow surgeons to achieve a high rate of success with mitral valve repair, even in complex cases, and mitral valve repair is associated with better long-term outcomes than valve replacement. However, in the setting of mitral valve surgical repair, systolic anterior motion (SAM) is a complication that determines the dynamic anterior movement of the mitral valve towards the interventricular septum during systole, and creates a left ventricular outflow tract obstruction associated with residual mitral regurgitation. Awareness of risk factors for SAM influences operative planning for repair. Predictors of SAM are known and can be definitively evaluated with intraoperative transesophageal echocardiography, but SAM still complicates mitral valve repair and, if untreated, negatively impacts short-term and long-term outcomes. A stepwise approach in SAM correction is advocated, consisting of medical therapy with aggressive volume-loading and beta-adrenoceptor blockade, but severe or persistent SAM requires surgical revision with a second cross-clamping or a redo procedure. The correct choice of surgical technique requires a deep understanding of the anatomical substrate of SAM, as SAM can be due to different mechanisms that require tailored surgical correction to avoid ineffective or potentially dangerous procedures. This paper reviews the mechanisms and predictors of SAM and summarizes the current concepts of intraoperative and postoperative SAM management.