The autonomic control of the transmural dispersion of ventricular repolarization in anesthetized dogs.
BACKGROUND
The initiation of ventricular arrhythmias is in part associated 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.


RESULTS
In 12 mongrel open chest anesthetized dogs, both sides of the cervical vagus nerves and stellate ganglia were crushed with a tight ligature. Right atrial pacing at 600 msec cycle length was begun after the sinus nodal area had been crushed. MAPs from the M region were measured by two needle electrodes that were supported by a W-shaped plastic frame. The epicardial, M region, and endocardial MAP durations at 90% repolarization (MAPD90) were 287+/-7, 315+/-7, and 290+/-8 msec, respectively. The MAPD90 from M cells was longer than that from Epi or Endo. Sympathetic stimulation shortened MAPD90 more in the M region (53+/-4 msec) than that in the Epi (27+/-3 msec) or Endo (26+/-4 msec). The transmural dispersion of repolarization during sympathetic stimulation was shorter than that of the control. Parasympathetic stimulation did not significantly affect any of the MAPD90 values. Simultaneous sympathetic and parasympathetic stimulation produced changes not significantly to those produced by sympathetic stimulation alone.


CONCLUSIONS
Our results suggest that sympathetic activity can reduce transmural dispersion of repolarization under autonomic control in the canine heart under baseline conditions.
Second Department of Internal Medicine, Shinshu University School of Medicine, Matsumoto, Nagano-ken, Japan. matakei@hsp.md.shinshu-u.ac.jp
M
M
Takei
Y
Y
Sasaki
T
T
Yonezawa
M
M
Lakhe
M
M
Aruga
K
K
Kiyosawa
D000200:Action Potentials / Q000502:physiology; D000768:Anesthesia, General; D000818:Animals; D001341:Autonomic Nervous System / Q000502:physiology*; D004285:Dogs; D004558:Electric Stimulation; D004594:Electrophysiology / Q000379:methods; D004699:Endocardium / Q000294:innervation / Q000502:physiology; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006352:Heart Ventricles / Q000294:innervation; D008297:Male; D010496:Pericardium / Q000294:innervation / Q000502:physiology; D013233:Stellate Ganglion / Q000502:physiology; D014630:Vagus Nerve / Q000502:physiology; D016276:Ventricular Function