Exercise training reduces ischemic myocardial dysfunction.
OBJECTIVE
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).


CONCLUSIONS
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.
Department of Integrative Physiology, University of North Texas Health Science Center, Fort Worth, TX 76107-2690, USA.
M A
MA
Brandt
P A
PA
Gwirtz
D000704:Analysis of Variance; D000818:Animals; D003326:Coronary Circulation / Q000502:physiology; D004285:Dogs; D005080:Exercise Test; D008863:Microspheres; D009200:Myocardial Contraction / Q000502:physiology; D017202:Myocardial Ischemia / Q000503:physiopathology*; D010805:Physical Conditioning, Animal / Q000502:physiology*; D011868:Radioisotopes
D011868:Radioisotopes