Improvement of ST Segment Depression by Gradual Recruitment of Collateral Circulation

Abstract

The purpose of the present study was to document that the coronary collateral vessels do not open immediately upon the occurrence of myocardial ischemia. A multistage bicycle exercise was performed to determine a maximal tolerable work load until the onset of angina and significant ST segment depression in 10 patients with well-developed collateral circulation. On a different day, exercise with the maximal tolerable work load was repeated for a comparable exercise duration. In 2 of the 10 patients, anginal pain was gradually alleviated despite the continuation of exercise with fixed work load. The extent of ST segment depression at 3 min of exercise with fixed work load was 0.20 ± 0.10 (SD) mV, significantly (p < 0.05) greater than 0.16 ± 0.08 mV at the end of exercise with fixed work load. In contrast, the rate-pressure product was smaller at 3 min than at the end of exercise with fixed work load (20,900 ± 5,500 vs. 22,700 ± 5,700 mm Hg · beats/min; p < 0.05). In 5 patients without well-developed collateral circulation, the extent of ST depression changed in parallel with changes in rate-pressure product during exercise with fixed work load. Thus, it is concluded that the delayed collateral opening plays a critical role in the pathogenesis of myocardial ischemia in patients with a totally occluded coronary artery.