The autonomic control of the transmural dispersion of ventricular repolarization in anesthetized dogs

Introduction: The initiation of ventricular arrhythmias is in part associat ed with autonomic nervous tone. We investigated the effects of Sympathetic and parasympathetic stimulation on the monophasic action potentials (MAPs) of the epicardium (EPI), mid-myocardial (M) region, and endocardium (Endo) in vivo. Methods and Results: In 12 mongrel open chest anesthetized dogs, both sides of the cervical vagus nerves and stellate ganglia were crushed with a tigh t ligature, Right atrial pacing at 600 msec cycle length was begun after th e sinus nodal area had been crushed. MAPs from the M region were measured b y two needle electrodes that were supported by a W-shaped plastic frame. Th e epicardial, M region, and endocardial MAP durations at 90% repolarization (MAPD(90)) were 287 +/- 7, 315 +/- 7, and 290 +/- 8 msec, respectively, Th e MAPD(90) from M cells was longer than that from Epi or Endo, Sympathetic stimulation shortened MAPD(90) more in the M region (53 +/- 4 msec) than th at in the Epi (27 +/- 3 msec) or Endo (26 +/- 4 msec), The transmural dispe rsion of repolarization during sympathetic stimulation was shorter than tha t of the control. Parasympathetic stimulation did not significantly affect any of the MAPD(90) values, Simultaneous sympathetic and parasympathetic st imulation produced changes not significantly to those produced by sympathet ic stimulation alone, Conclusion: Our results suggest that sympathetic activity can reduce transm ural dispersion of repolarization under autonomic control in the canine hea rt under baseline conditions.