O₂ Extraction During Exercise Determines Training Effect After Cardiac Rehabilitation in Myocardial Infarction

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Correlations between baseline hemodynamic and oximetric variables during an invasive exercise test and an improvement in peak oxygen uptake (peak Vo₂) after exercise training (ET) were examined in 20 patients who participated in a cardiac rehabilitation program after acute myocardial infarction (AMI). Peak Vo₂ significantly increased by 23±21% (p<0.01) after ET and the improvement best correlated with the change in O₂ extraction fraction ([arterial O₂ content - venous O₂ content] / arterial O₂ content) during an exercise test before ET (r=-0.61, p<0.01). Exercise capacity was improved to a greater extent by ET in patients with a smaller increase in O₂ extraction fraction during an exercise test before ET. Thus, O₂ extraction fraction during an exercise test before ET may be a useful predictor of the improvement in exercise capacity after ET in post-AMI patients. (Circ J 2002; 66: 891 - 896)