PO-02-152 EFFECTS OF SYMPATHETIC STIMULATION ON REPOLARIZATION AND ARRHYTHMOGENESIS DURING LEFT LATERAL MYOCARDIAL ISCHEMIA

Abstract

Left stellate ganglion stimulation (LSGS) is arrhythmogenic during acute myocardial ischemia of the anterior wall of the left ventricle. We hypothesized, as a counterpart, that right stellate ganglion stimulation (RSGS) is proarrhythmic when ischemia is produced by occlusion of the circumflex coronary artery. In 7 anesthetized female open-chested pigs, ventricular repolarization was measured in unipolar electrograms from 128 epicardial sites on the left lateral ventricular wall in an electrode grid of 14x30 mm (interelectrode distance 2 mm). Seven subsequent episodes of 5 minutes of acute ischemia (5 minutes occlusion of the circumflex coronary artery with 20 minutes reperfusion). Right atrial pacing was performed throughout the experiment at cycle length of 450 ms. The second occlusion served as a control. During the third and fourth occlusion, left or right stellate ganglion stimulation (LSGS or RSGS), respectively, was initiated after 3 minutes of ischemia for 30 seconds. The protocol was repeated after decentralization of both stellate ganglia and bilateral cervical vagotomy. Between 3 and 5 minutes of ischemia, RSGS caused a median of 9 (interquartile range 3-12), ventricular premature beats and in 2 instances ventricular tachycardia and fibrillation. The number of ventricular premature beats was significantly less during LSGS and control conditions (Figure, panel A), during which no ventricular tachycardia or fibrillation occurred. Following decentralization, RSGS was no longer significantly more arrhythmogenic than LSGS or control conditions (Figure, panel A). Additionally, we found that LSGS-induced changes in repolarization are evident in non-ischemic tissue, but not in ischemic tissue, during coronary occlusion (Figure, panel B, note the overlapping T-waves in the ischemic region). LSGS no longer has an effect on myocardium that has been ischemic for 3 minutes by occlusion of the circumflex coronary artery. RSGS was arrhythmogenic in this setting, while LSGS was not. This supports the clinical findings that bilateral sympathectomy is superior to left sympathectomy alone.