The physiological response of the heart to segmental myocardial resection

Abstract

In 28 dogs the right and left ventricular stroke work, dp/dt and ventricular function curves (VFC) were obtained before and after resection of a segment of the anterior wall of the left ventricle. In 9 experiments, acute ischemia of the segment was produced by ligating the anterior descending branch of the left coronary artery. In all dogs cervical vagotomy was done before or after ischemia or resection. In normal hearts, after resection, marked depression in VFC were noted. After vagotomy the VFC showed a shift to the left. After ischemia, there was a significant decrease in stroke work but with a nonsignificant shift to the left of the VFC after vagotomy. In the majority of dogs, upon increasing the ventricular end-diastolic pressure, heart rate deceleration and peripheral vasodilation occurred. After ischemia, the magnitude of this response showed a greater decline with an occasional change in the pattern of these parameters which was not altered by vagotomy. After resection of the ischemic area in two thirds of the dogs the VFC showed improvement with a shift to the left. These experiments indicate that in spite of the operative trauma the immediate performance of the post-ischemic heart in the absence of the ischemic segment is somewhat improved. The results also suggest that the cardiac and extra-cardiac reactions, due to the stimulation of induced ventricular ischemia receptors, are not totally mediated via the vagus nerve and they remain active after removal of the ischemic segment.