Influence of Sympathetic Nerve Activity on Ventricular Arrhythmogenicity in the Dog with Chronic Hypokalemia

Abstract

To examine the influence of sympathetic nerve activity on ventricular arrhyth mogenicity in the dog with chronic hypokalemia, an electrophysiologic study was performed before and after bilateral stellectomy (BS) in 10 dogs with chronic hypokalemia (2.8 ± 0.1 mEq/L), which was created by feeding a low-potassium diet and by administering furosemide over a four-week period, and the results were compared with those obtained from 10 dogs with normokalemia (4.7 ± 0.3 mEq/L) from being fed an ordinary diet over a four-week period.

Before BS the incidence of electrically induced ventricular arrhythmias was higher in the hypokalemic than in the normokalemic dogs. After BS it was decreased considerably in the hypokalemic but not in the normokalemic dogs. Heterogeneity of effective refractory period (ΔERP), which was determined as the difference between the longest and shortest effective refractory periods in three sites of the right and left ventricles, was greater in the hypokalemic than in the normokalemic dogs before BS. The ΔERP decreased slightly in the two groups both before and after BS. There was, however, no significant difference in ΔERP in the two groups both before and after BS. Ventricular fibrillation threshold (VFT) was significantly lower in the hypokalemic dogs than in the nor mokalemic dogs before BS (p< 0.005). VFT was elevated in the two groups after BS. Percent increase in VFT after BS was significantly greater in the hypoka lemic than in the normokalemic dogs. In conclusion, sympathetic nerve activity may play an important role in the increase in ventricular arrhythmogenicity in the presence of chronic hypokalemia.