Local ventricular repolarization changes due to sympathetic nerve-branch stimulation.

Functional distributions of individual cardiac nerves distal to the stellate ganglia were determined in 30 open-chest, anesthetized dogs by mapping sites of refractory-period shortening during stimulation of the nerves. On the right, recurrent cardiac nerve stimulation produced marked shortening of refractory periods in the interventricular septum, and lesser changes on the anterior heart surface. On the left, ventromedial cardiac nerve stimulation shortened refractory periods in a similar distribution, but changes were not marked as with the recurrent cardiac nerve. The other left-side nerve that produced repolarization changes, the ventrolateral cardiac nerve, produced marked refractory-period changes on the posterior heart surface. Its distribution showed little overlap with that of the ventromedial or recurrent cardiac nerves. T waves inverted in an electrocardiographic Y lead during recurrent cardiac and ventromedial cardiac nerve stimulation, while ventrolateral cardiac nerve stimulation increased the positivity of T waves in that lead. The cardiac distributions of individual nerves documented in this study provide an anatomical basis for localized alterations in ventricular electrophysiologic properties.