Dynamic narrowing of left ventricular outflow tract-Possible mechanism of latent left ventricular outflow tract obstruction.

It has been reported that left ventricular outflow tract (LVOT) obstruction can be provoked in patients even without significant left ventricular hypertrophy. We experienced a 74-year-old man with mild degree of left ventricular hypertrophy and latent LVOT obstruction which was successfully treated by alcohol septal ablation. LVOT was not narrow at end-diastole, but proximal septum was protruding further into LVOT during the ejection period, producing a dynamic narrowing of the LVOT. Alcohol septal ablation did not reduce the interventricular septal thickness nor enlarge LVOT. However, it limited the excursion of proximal septum. The effect of the treatment suggested the importance of the dynamic nature of LVOT in the mechanism of latent LVOT obstruction in this case.