This study indicates that in dogs, ischemic injury to just the ventricular septum has little effect on left ventricular function. The data demonstrate that ischemic injury to either the right ventricular free wall or the ventricular septum alters right ventricular function and/or compliance, suggesting that both regions play a role in maintaining right ventricular performance. That septal contraction supports right ventricular function may explain why in earlier studies, right ventricular pressure development and output were little affected by severe injury to the free wall.