Acute Severe Functional Mitral Regurgitation After Non-Mitral Valve Cardiac Surgery—Left Ventricular Dyssynchrony as a Potential Mechanism

Functional mitral regurgitation (MR) describes valve leakage in the absence of disease or damage to the mitral leaflets or subvalvular apparatus. Significant, new functional MR after cardiopulmonary bypass (CPB) may result from a number of intraoperative processes, including left ventricular (LV) ischemia and enlargement, left atrial enlargement secondary to increased filling pressure, and systolic anterior motion of the mitral valve after mitral repair. Assessment of new MR after CPB is important because it may direct hemodynamic maneuvers or prompt reinitiation of CPB if surgical intervention is deemed necessary. Described extensively in the electrophysiology literature but underreported as a cause of MR after CPB, LV dyssynchrony represents another possible mechanism of functional MR, in which resynchronization of conduction via pacing maneuvers may prove beneficial. Herein, a series of 4 patients in whom new MR was found after non-mitral valve cardiac surgery in the setting of normal LV systolic function is presented, and LV dyssynchrony is proposed as a major contributing factor. The findings suggested that the concomitant observation of new or worsened functional MR, together with normal global and regional LV systolic function, should lead the clinician to consider ventricular dyssynchrony as a possible cause. Attempts to improve or alter ventricular conduction should be considered before contemplating a return to CPB for mitral valve intervention.