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Depression of regional blood flow and wall thickening after brief coronary occlusions
Insights
A 15-minute coronary occlusion in dogs led to reduced myocardial blood flow and impaired heart muscle function. Reperfusion did not fully restore blood flow or function, particularly in the endocardium, for hours.
Area of Science:
- Cardiovascular Physiology
- Myocardial Ischemia and Reperfusion
Background:
- Coronary artery occlusion triggers ischemia, impacting cardiac function.
- Understanding reperfusion's effects on myocardial blood flow and function is crucial.
Purpose of the Study:
- To investigate the functional and hemodynamic consequences of a 15-minute coronary occlusion and subsequent reperfusion.
- To assess the duration of impaired myocardial blood flow and regional function post-reperfusion.
Main Methods:
- Conscious dogs were instrumented to measure left ventricular pressure, dP/dt, regional wall thickening, electrograms, and myocardial blood flow.
- Coronary occlusion was maintained for 15 minutes, followed by reperfusion.
- Measurements were taken during occlusion, reperfusion, and for several hours afterward.
Main Results:
- Coronary occlusion significantly reduced regional myocardial blood flow and eliminated systolic wall thickening in the ischemic zone.
- ST-segment elevation occurred during occlusion, resolving rapidly after reperfusion.
- Despite rapid resolution of ST elevation and reactive hyperemia, systolic wall thickening and endocardial blood flow remained depressed for over 3 hours post-reperfusion.
Conclusions:
- A 15-minute coronary occlusion followed by reperfusion results in prolonged depression of regional myocardial blood flow, especially in endocardial layers.
- This persistent reduction in blood flow correlates with sustained impairment of regional myocardial shortening and wall thickening.
Abstract:
The effects of a 15-min coronary occlusion and subsequent reperfusion were investigated in conscious dogs previously instrumented for measurement of left ventricular pressure, dP/dt, regional wall thickening, electrograms, and myocardial blood flow. Coronary occlussion reduced overall left ventricular function only slightly but eliminated systolic wall thickening in the ischemic zone and reduced regional myocardial blood flow in the ischemic zone from 1.04 +/- 0.04 to 0.27 +/- 0.02 ml/min per g and the endo/epi flow ratio from 1.23 +/- 0.04 to 0.44 +/- 0.04, while S-T segment elevation increased from 1.1 +/- 0.3 to 8.2 +/- 0.9 mV. After release of the occlusion, S-T segment elevation disappeared within 1 min while reactive hyperemia in the previously occluded artery and a transient increase in cardiac diastolic wall thickness occurred and then subsided by 15 min. In contrast, systolic wall thickening and the endo/epi flow ratio remained significantly depressed for more than 3 h. Thus reperfusion after a 15 minute coronary occlusion results in a prolonged period of reduced regional myocardial blood flow, particularly in the endocardial layers, which correlates with the prolonged depression of regional myocardial shortening and wall thickening.