Septal myectomy and myotomy attenuate left ventricular hyper-contractility in a child with hypertrophic obstructive cardiomyopathy.

Septal hyper-contractility is thought to be the principal cause of significant left ventricular outflow tract obstruction (LVOT) and systolic anterior motion (SAM) of the mitral valve by making the distance between the mitral valve and papillary muscle shorter. A seven-year-old patient with severe hypertrophic obstructive cardiomyopathy underwent direct interventricular septal myectomy/myotomy using the resection/crush method to modify hyper-contractility. The procedure successfully reduced the pressure gradient from 180 mmHg to 7.6 mmHg, and systolic anterior movement of the mitral leaflet disappeared. Mitral regurgitation improved from grade 2 to grade 0. Postoperative echocardiographic vector velocity imaging (VVI) study revealed a reduced twist angle, depicting attenuated ventricular contraction power from a maximum twist 17.9° to 7.9°. Perioperative VVI revealed that interventricular septal myectomy/myotomy is useful, not only in reducing LVOT obstruction, but also in reducing hyper-contractility, which increases the distance from the mitral valve to the papillary muscle and relieves SAM.