Effects of bilateral and unilateral stellate stimulation on canine ventricular refractory periods at sites...

The efffects of unilateral right, unilateral left, and bilateral stellate stimulation on ventricular refractory periods at sites of overlapping cardiac sympathetic innervation were studied in 11 pentobarbital anesthetized dogs. The stellates were stimulated with 10 Hz pulses 4 msec in duration with intensities strong enough to produce T wave changes in a vertical ECG lead and just below the intensity at which control of drive of the ventricle at a 400-msec cycle length was lost. Refractory periods shortened more with left stellate stimulation, 17.8 +/- 5.9 msec (mean +/- SD) than with right stellate stimulation, 10.3 +/- 5.1 msec, P less than 0.001. During bilateral stimulation, shortening of refractory periods was no greater whether stimulation was applied first to the left and then right stimulation was added, 19.7 +/- 6.9 msec, or the stimulation was applied first to the left and then right stimulation was added, 18.3 +/- 6.5 msec. The shortening of refractory periods with bilateral stellate stimulation was not significantly different from that with left stellate stimulation alone. The results of this study suggest that ventricular recovery properties in areas of overlapping cardiac sympathetic innervation are less influenced by increases in tone of the right sympathetics than by increases in left sympathetic tone. In addition, the findings indicate that a bilateral increase in cardiac sympathetic tone has no greater effect on recovery properties than the effects of the left cardiac sympathetics alone.