Background: Exercise training leads to an improvement of the coronary collateral circulation. However, clinical relevance of coronary collaterals is still controversial with the association between collateral growth and ischemic threshold still unclear.
Purpose: We aimed to investigate in the impact of exercise training on the ischemic threshold. In addition, we elucidated the association between the change in coronary collateral growth and ischemic threshold.
Methods: We randomized 60 patients with significant CAD (FFR≤0.75) to high-intensity exercise (group A, 20 patients) or moderate-intensity exercise (group B, 20 patients) for 4 weeks or to a control group (group C, 20 patients). At baseline and after 4 weeks, the coronary collateral flow index (CFI) was measured invasively and the ischemic threshold was assessed in ergospirometry expressed in heart rate and watt.
Results: Four weeks of exercise training resulted in a significant increase in ischemic threshold as compared to usual care with no difference between the high- and moderate-intensities. Spearman rank correlation revealed a significant association between the change in CFI and change in ischemic threshold after 4 weeks (Spearman correlation coefficient 0.425, p=0.006). Mean heart rate at ischemic threshold assessed in ergospirometry at baseline was 113±18 bpm with no statistical differences between groups (P=0.30). At 4 weeks, we observed a significant increase in heart rate at ischemic threshold in patients who underwent exercise training compared to the control group (group A compared to group C: P=0.015; group B compared to group C: P=0.001) with no difference between high- and moderate intensities (P=1.0). In detail, after 4 weeks, mean heart rate at ischemic threshold increased from 118±19 bpm to 132±20 bpm in group A and from 107±22 bpm to 132±21 bpm in group B. We noted no change in mean heart rate at ischemic threshold after 4 weeks in group C (from 116±13 bpm to 117±13 bpm).
Conclusion: High- and moderate-intensity exercise training for 4 weeks resulted in a significant increase in ischemic threshold. In addition, we observed a significant correlation between change in CFI and change in ischemic threshold after 4 weeks (P=0.034, correlation coefficient 0.336).