Objectives: 

Chronic exercise exhibits myocardial electrophysiological protective effects. It has been implicated IKATP blockade in the protective effect of exercise, in cases of activation of that current (i.e.: acute ischemia). Indeed, the administration of glibenclamide, an oral antidiabetic sulfonylurea class and also blocker of the above mentioned current, has electrophysiological effects similar to physical exercise in acute ischemia of myocardium. The aim of the present study is to analyze the effect of chronic exercise and glibenclamide on the frequency of myocardial activation during ventricular fibrillation(VF) under normoxic conditions, in order to evaluate the existence of electrophysiological similarities between the two situations (training and glibenclamide treatment), as it occurs in acute regional ischemia.

Materials: 

NZW rabbits (n=9) were submitted to a six-week exercise program, and 11 rabbits (glibenclamide 10mM group) and 11 rabbits (control group) were not trained. After this period, rabbits were anaesthetized (ketamine 10 mg/kg i.v.), euthanized and the hearts excised, isolated and perfused in a Langendorff system. A pacing electrode and a plaque with 256 recording electrodes were positioned on the left ventricle. VF was induced at increasing frequencies and the VF dominant frequency(DF) was determined after 5 min of the arrhythmia under normoxic perfusion. An ANOVA test was applied (significance p<0,05).

Results: 

Mean DF of VF was lower in the trained group than in the control group (12,67±0,65 n=9 vs. 14,58±1,66Hz n=11) and trended (p=0,06) to be lower than in the glibenclamide group (12,67±0,65 n=9 vs. 13,91±1,61Hz n=11). No differences were observed between control and glibenclamide group.

Conclusions: 

Physical training produces electrophysiological effects that decrease VF frequency in normoxic conditions. Unlike what happens in acute ischemia, glibenclamide does not exert the same effects as exercise in normoxic situation.

Support: DEP2010-22318-C02-01, PROMETEO2010/093