[Walk-through phenomenon by gradual recruitment of collateral circulation]

The present study was performed to investigate whether coronary collateral vessels open immediately after occurrence of myocardial ischemia. Multistage bicycle exercise was performed to determine the maximum tolerable workload until the onset of angina and significant ST segment depression in 10 patients with well-developed collateral circulation. On a different day, exercise using the maximum tolerable workload was repeated for comparable exercise durations. In two of the 10 patients, anginal pain was gradually alleviated despite the continuation of exercise using the fixed workloads. The extent of ST segment depression during three min exercise with the fixed workload was 0.20 +/- 0.10 (SD) mV, which was significantly (p less than 0.05) greater than 0.16 +/- 0.08 mV at the end of exercise with fixed workload. By contrast, the pressure-rate product was smaller at three min than at the end of exercise using the fixed workload (20,900 +/- 5,500 vs 22,700 +/- 5,700 mmHg-beats/min; p less than 0.05). It was concluded that delayed collateral openings play a critical role in the pathogenesis of the walk-through phenomenon.