Paradoxical Increase in Left Ventricular Outflow Tract Gradient in a Patient Undergoing Mitral Valve Repair and Septal Myectomy

The Doppler-derived gradient depends on the magnitude of the flow across a narrowed orifice and the alignment of the Doppler with the flow. Septal myectomy is indicated in symptomatic obstructive hypertrophic cardiomyopathy (HCM) patients with peak instantaneous gradient > 50 mmHg. Chordal rupture has been reported infrequently in obstructive HCM patients, which may hide left ventricular outflow tract (LVOT) gradient because of a decreased forward flow across the LVOT, posterior shift of the coaptation point due to flail posterior mitral leaflet widening the LVOT, or absence of systolic anterior motion (SAM). An increase in the flow across the LVOT will occur after mitral valve repair, which may manifest as an increased LVOT gradient. In a clinical scenario of the simultaneous presence of severe mitral regurgitation, severe septal hypertrophy, and low gradient across the LVOT, the dilemma is whether to perform a septal myectomy in addition to MV repair. An unexpected increase in the LVOT gradient occurred despite septal myectomy in a patient with mitral regurgitation after mitral valve repair. We discuss the necessity of septal myectomy in the presence of a low LVOT gradient, severe mitral regurgitation, and posterior shift of the coaptation point due to posterior leaflet flail and chordal rupture.