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Dynamic Left Ventricular Outflow Obstruction and Systolic Anterior Motion of the Mitral Valve Complicating Surgical Aortic Valve Replacement.

BESIDES PREVENTING REGURGITATION, the mitral valve controls ventricular inflow and outflow patterns. The position and angle of the mitral orifice opening (mitral-aortic annular plane angle 4120 degrees) and the shape of the anterior leaflet, direct ventricular inflow along the posteriorlateral wall, toward the apex, creating a flow vortex that directs flow, unhindered, along the anterior-septal wall into the left ventricular outflow tract (LVOT). During ventricular systole, the annulus contracts across 3 planes, elevating the anterior portion and moving the entire annulus (and leaflets) posterior, thus enlarging the LVOT. Together, blood flows in and out of the ventricle unimpeded. Shapeton et al. presented a case of dynamic left ventricular outflow tract obstruction (dLVOTO) after aortic valve replacement (AVR) for aortic stenosis (AS). Classically, dLVOTO is associated with the obstructive form of hypertrophic cardiomyopathy (HOCM), a “heterogeneous” disease presenting with asymmetric or concentric hypertrophic patterns, both patterns having the ability to cause obstruction to outflow at either the apex, midcavity, or subvalvular regions. dLVOTO at the subvalvular level may be associated with systolic anterior motion (SAM) of the mitral valve, mitral regurgitation (MR), and hemodynamic instability. The case presented reminds us that outflow tract obstruction is not unique to HOCM or mitral valve repair. The occurrence of dLVOTO after AVR has been described in many case reports and case series since the 1980s and 1990s. Most cases occur after AVR for AS; however, cases have been reported in those presenting with aortic insufficiency. An integrated mechanism including ventricular anatomy and the mitral apparatus has been described to explain the occurrence of dLVOTO across different patient types. Two of the unifying features include a short distance between the mitral coaptation point and the ventricular septum (C-Sept distance o2.5 cm) and ventricular hypertrophy (415 mm). A mitral-aortic annular plane angle o120 degrees means that the mitral orifice opens more anteriorly, placing the mitral leaflets nearer to the