Effects of exercise on the coronary and collateral vasculature of beagles with and without coronary occlusion.

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Abstract
The purpose of this study was to determine if exercise stimulates coronary collateral vessel growth and if exercise after coronary occlusion can promote additional collateral growth. One group of 10 beagles served as control. The second group considered of 10 normal beagles exercised at 50% of maximum O2 consumption 7 days/week for 6 weeks. In the third group, the circumflex was occluded (Ameroid method) in eight beagles for 5 months. In the fourth group, seven beagles were exercised for 8 weeks following 3 months of circumflex occlusion. The coronary and collateral circulation was assessed, using an isolated heart preparation. It was found that exercise did not stimulate collateral growth in normal beagles. However, exercise after coronary occlusion doubled collateral conductance to be impaired vascular bed compared to animals with only coronary occlusions. Our study shows that, in beagles with coronary occlusion, exercise after a 3-month convalescent period promotes epicardial and intramyocardial (septa) collateral growth. Coronary reserve in the trained animals returned to 52% of initial capacity vs. 34% for the untrained animals.