The duration of coronary occlusion influences adrenergic contributions to reperfusion ventricular arrhythmias

Abstract

To study the role of the adrenergic nervous system in the genesis of nonlethal reperfusion arrhythmias, the proximal left anterior descending coronary artery was occluded for either 1 or 3 hours in 48 open-chest dogs anesthetized with alpha-chloralose. Heart rate was controlled (90 to 110 beats/min) by bilateral vagotomy and continuous right vagal stimulation. Dogs were treated with either saline, timolol (0.1 mg/kg), or prazosin (0.5 mg/kg) 15 minutes prior to reperfusion. Reperfusion after 1 hour of occlusion in saline-treated dogs evoked sustained polymorphic ventricular tachycardia (204 +/- 9 beats/min) that reverted to sinus rhythm by 15 minutes of reperfusion. The maximum rate of ventricular tachycardia was significantly reduced by both prazosin and timolol. Both drugs also caused about a 50% reduction in the total number of ectopic beats in the first 10 minutes of reperfusion. With a 3-hour occlusion, reperfusion in saline-treated dogs caused sustained polymorphic ventricular tachycardia (135 +/- 15 beats/min) which persisted for several hours. Neither timolol nor prazosin significantly altered the ventricular ectopic rate in these dogs. Furthermore, bilateral stellate transection, left stellate stimulation, isoproterenol (0.5 mg/kg), or methoxamine (100 ug/kg) all failed to alter the ventricular ectopic rate in the saline-treated dogs. Ventricular ectopy induced by reperfusion after a 1- or 3-hour occlusion was overdriven in all dogs by rapid atrial pacing. The results suggest that the nature of reperfusion-induced ventricular ectopy is highly dependent upon the preceeding duration of coronary occlusion.(ABSTRACT TRUNCATED AT 250 WORDS)