Purpose: This study tested the hypothesis that exercise training improves myocardial blood flow and regional myocardial contractile function in a lateral border zone located adjacent to the ischemic zone during coronary artery occlusion. Methods: Fourteen dogs were subjected to either 12 wk of dynamic exercise training or cage rest. Dogs were anesthetized and instrumented to assess regional myocardial contractile function (percent segment length shortening and rate of shortening) and regional myocardial blood flow (tracer microspheres) in the central ischemic, lateral border, and nonischemic zones. Measurements were made preocclusion and at 2 min and 3 h after occlusion of the left anterior descending coronary artery (CAO). Results: Contractile function and regional myocardial blood flow were not affected by CAO in the nonischemic zone in both cage-rested and exercise trained dogs. Regional myocardial contractile function and blood flow in the lateral border zone were significantly higher in exercise trained dogs compared with cage-rested dogs, both at 2 min and 3 h after CAO. Ischemic dysfunction was similar in the central ischemic zone in both cage-rested and exercise trained dogs both at 2 min and 3 h after CAO. Regional myocardial blood flow was similarly reduced in the ischemic zone in both groups after 2 min of CAO, but was significantly higher in the inner (subendocardial) region of the exercised trained hearts after 3 h (P < 0.05). Conclusion: These data suggest that there was greater border zone perfusion in exercise trained animals during prolonged CAO, which was associated with significantly improved myocardial contractile function.
- Myocardial blood flow
- Radioactive microspheres
- Regional myocardial contractile function
- Segment length shortening