To evaluate the mechanism of the abnormal motion of the interventricular septum (IVS) seen echocardiographically in some patients with relatively delayed ventricular activation, we simultaneously recorded high-fidelity left and right ventricular pressures and electrograms and echocardiograms of the IVS in nine open-chest dogs. During sinus rhythm and during left IVS pacing, the IVS was activate...
