Importance of collateral circulation to preserve the exercise capacity in patients with coronary artery disease

We studied the effects of coronary collaterals on exercise capacity in relation with the coronary flow reserve. Thirty-one patients with single vessel disease of the left anterior descending artery (LAD) were selected using coronary angiography. Thirteen of them had angiographical collaterals. A Doppler coronary catheter was positioned in the proximal portion of the LAD, and the resting and peak coronary flow velocity was measured using an intracoronary injection of 6 ml of contrast material. Peak to resting velocity ratio was calculated as an index of the coronary flow reserve. Multi-stage treadmill exercise ECG test was performed, and the end point of the exercise was 0.1 mV depression of ST segment. The exercise capacity was expressed as the ratio of maximal to resting double product. In patients without collaterals, peak to resting coronary flow velocity ratio was correlated with double product ratio (r = 0.94, p less than 0.01). But in patients with collaterals, double product ratios were higher than those in patients without collaterals. We conclude that coronary collaterals preserve exercise capacity in spite of the low coronary flow reserve in the recipient coronary artery.