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Improvement of ST segment depression by gradual recruitment of collateral circulation
1Second Department of Internal Medicine, Toyama Medical and Pharmaceutical University, Japan.
Insights
Coronary collateral vessels do not open immediately during myocardial ischemia. Delayed collateral opening is critical in the development of ischemia in patients with totally occluded coronary arteries.
Area of Science:
- Cardiology
- Physiology
Background:
- Myocardial ischemia occurs when blood supply to the heart muscle is insufficient.
- Coronary collateral circulation is a network of vessels that can supply blood to ischemic areas.
- The timing of collateral vessel activation is crucial for understanding ischemic heart disease.
Purpose of the Study:
- To investigate the immediate response of coronary collateral vessels during myocardial ischemia.
- To determine if collateral vessels open instantaneously upon the onset of ischemia.
- To elucidate the role of delayed collateral opening in the pathogenesis of myocardial ischemia.
Main Methods:
- Multistage bicycle exercise tests were conducted in 10 patients with well-developed collateral circulation.
- Maximal tolerable workload was determined based on angina and ST segment depression.
- Exercise at a fixed workload was repeated to assess collateral response over time.
Main Results:
- In patients with well-developed collaterals, anginal pain gradually subsided during sustained exercise.
- ST segment depression was significantly greater at 3 minutes compared to the end of exercise.
- Rate-pressure product was lower at 3 minutes than at the end of exercise, indicating a delayed hemodynamic response.
Conclusions:
- Coronary collateral vessels do not open immediately upon the onset of myocardial ischemia.
- Delayed collateral opening plays a critical role in the pathogenesis of myocardial ischemia, particularly in cases of totally occluded coronary arteries.
- These findings have implications for understanding and managing ischemic heart disease.
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 less than 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 less than 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.