Left Ventricular Wall‐Motion Changes During Eccentric Ventricular Activation in Hypertrophic Obstructive Cardiomyopathy Patients

Permanent atrial synchronized right ventricular pacing (RVP) has been shown to induce subaortic pressure gradient reduction and to lead to clinical improvement in patients suffering from hypertrophic obstructive cardiomyopathy (HOCM). It has therefore been proposed as an alternative therapy to surgery for patients refractory to drug therapy. The mechanisms underlying these beneficial effects are, however, unclear, but the electrically induced alteration of left ventricular (LV) activation sequence appears to play a major role. In this article, I summarize the data relative to the specific effects of RVP and left bundle branch block on LV contraction in normal subjects and in cardiomyopathies other than hypertrophic. I also review the characteristics of regional wall motion in HOCM, then the current data on left ventricular wall-motion changes during eccentric ventricular activation in HOCM patients equipped with a dual chamber pacemaker. On the basis of the most recent studies, preexcitation of the interventricular septum by a RV apical stimulation alters septal motion by reducing its motility or by inducing a paradoxical motion, which enlarges the LV outflow tract and thereby reduces subaortic obstruction.