[Does ST-elevation in stress ECG depend on the extent of collateral circulation?]

As a possible cause of exercise-induced ST-elevation in patients without myocardial infarction, a poor or absent coronary circulation to the poststenotic coronary segment was postulated. To check this thesis, we examined 10 patients (pts.) with ST-elevation, respectively, ST-depression and comparable coronary status (coronary score 12 vs. 12; mean stenosis diameter 86 vs. 85%) and exercise parameters (work load 150 vs. 137.5 Watts; exercise duration 2.8 vs 3.5 min) with regard to their collateral circulation. In the group with ST-elevation there were nine pts. with severe proximal stenosis of the left anterior descending artery (LAD) and one pt. with a stenosis in the middle third of the right coronary artery. The 10 patients with ST-depression had a proximal stenosis in the LAD. The extent of the angiographically seen collaterals was equal in both groups. As a result, this study demonstrates that the size of the collateral circulation has no influence on the exercise-induced ST-elevation. The most plausible cause of exercise-induced ST-elevation is a functional decrease of the lumen of a severe stenosis.