Objectives: 

The enhanced electrophysiological heterogeneity constitutes a substrate for reentrant arrhythmias as ventricular fibrillation (VF). It has been also reported that physical training could protect against cardiac sudden death, and it has been proposed as an antiarrhythmic intervention, although the exact underlying protecting mechanisms are not completely understood. Moreover it is known that myocardial activation during VF is determined by properties as refractoriness, heterogeneity, etc. Our hypothesis is that chronic physical exercise reduces the complexity of myocardial activation during VF. The demonstration of this hypothesis would imply that the training operated beneficially on determined properties of the electrical activation complexity during VF.

Materials: 

Eight rabbits were trained during six weeks, and nine were housed during the training time. After training period the rabbit hearts were excised, isolated and perfused in a Langendorff system. A pacing electrode and a plaque with 256 recording electrodes were positioned on the left ventricle, and VF was induced. Electrical activation maps were determined during the arrhythmia. Electrical activation maps were determined during the arrhythmia. Activation complexity was expressed by numeric values 1,2,3,4 y 5 depending on the number of activations in a given time. The complexity of maps was determined 5 minutes after VF. A student t-test was applied to compare the complexity. To compare the percentage of complexity levels a squared chi test.

Results: 

The analysis of the activation maps during VF showed lesser complexity in the trained group than control group (41,3±4,9vs.34,6±7,5), with higher 1-2 type maps and lesser percentages of type 3,4 and 5(p=0,005).

Conclusions: 

Chronic physical exercise could operate in a beneficial way on the electrophysiological properties related to the complexity of myocardial activation during VF and thus to the onset of this arrhythmia.

Support: DEP2007-73234-C03-01, Prometeo 2010-093