Aim: 

To investigate the effects of chronic exercise on the modification of the spectral characteristics of ventricular fibrillation (VF) produced by acute myocardial ischemia, on the basis of the reported relation between the decrease of VF frequency induced by ischemia and the metabolic myocardial damage.

Methods: 

Seven rabbits were exercised following a chronic exercise protocol on treadmill (trained group) and another seven rabbits (control group) were housed during the training period. When the chronic exercise program was finished, rabbits were anaesthetized, sacrificed and the heart 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 triggered by pacing at increasing frequencies and myocardial ischemia was induced through circumflex coronary artery occlusion. DF of VF was determined by spectral analysis. VF was recorded before and at different times after coronary occlusion (15, 30, 45, 60, 90, 120, 150, 180, 210, 240, 270, and 300s). An ANOVA test (repeated measures) was applied to compare DF of VF through time.

Results: 

In control hearts, DF of VF decreased (p<0.05) 15s after coronary occlusion with respect to basal value (12.920.4 versus 14.070.8Hz), and the DF decrease was maintained during the five minutes after coronary occlusion. Acute coronary occlusion did not modify DF of VF in the trained group.

Conclusion: 

The maintenance of the DF of FV after acute coronary occlusion exhibited by physical training can be the expression of a protective effect on ischemic myocardial damage.

Supported by MEC (DEP2006-56208-C03-01 and SAF2007-62412).