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Increased protection of the ischemic myocardium by decreased aortic pressure
1Department of Geriatrics, Keio University School of Medicine, Tokyo, Japan.
Insights
Elevating aortic pressure can worsen myocardial oxygen supply during acute myocardial ischemia. Reducing systemic blood pressure before reperfusion therapy may enhance myocardial protection in patients with acute myocardial ischemia.
Area of Science:
- Cardiovascular Physiology
- Myocardial Ischemia Research
Background:
- Elevated aortic pressure increases myocardial oxygen demand and supply.
- The net effect of increased aortic pressure on myocardial protection during ischemia is unclear.
Purpose of the Study:
- To review existing data on aortic pressure's effect on coronary circulation and ischemic myocardium.
- To propose a strategy for enhancing myocardial protection during acute myocardial ischemia.
Main Methods:
- Review of published data on coronary pressure-flow relationships.
- Analysis of effects on ischemic myocardium in canine models.
Main Results:
- Aortic pressure elevation shifts the coronary pressure-flow line rightward, indicating a worsened oxygen supply/demand ratio.
- Early reperfusion is the primary method for protecting ischemic myocardium.
Conclusions:
- Aortic pressure elevation can be detrimental to the oxygen balance in ischemic myocardium.
- Reducing systemic blood pressure until reperfusion therapy is initiated may improve myocardial protection in acute myocardial ischemia.
Abstract:
The elevation of aortic pressure increases myocardial oxygen consumption and increases the blood supply to the myocardium. It is not obvious whether elevated systemic arterial pressure would enhance or diminish myocardial protection during acute myocardial ischemia. This report reviews previously published data on the effects of aortic pressure elevation on the coronary pressure-flow relationship, and on the ischemic myocardium in the dog. The shift of the maximally-dilated coronary pressure-flow line to the right on the pressure-flow diagram is an indication of the deterioration of the oxygen supply/demand ratio caused by aortic pressure elevation. The only maneuver recognized for protecting the ischemic myocardium is early reperfusion. In patients with de novo acute myocardial ischemia, we propose that myocardial protection can be enhanced by reduction of systemic blood pressure until coronary reperfusion therapy is initiated.