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Oxygen consumption and coronary reactivity in postischemic myocardium
D D Laxson1, D C Homans, X Z Dai
1Department of Medicine, University of Minnesota Medical School, Minneapolis.
Circulation Research
|January 1, 1989
Summary
Postischemic myocardial contractile dysfunction in dogs did not decrease oxygen consumption. However, coronary reactive hyperemia was reduced, indicating altered vascular function despite preserved blood flow.
Area of Science:
- Cardiology
- Physiology
- Vascular Biology
Background:
- Myocardial stunning, or reversible contractile dysfunction, occurs after ischemia.
- Understanding coronary vascular responses during stunning is crucial for cardiac health.
- Previous studies have yielded conflicting results on oxygen consumption and blood flow during myocardial stunning.
Purpose of the Study:
- To investigate coronary vascular responses in stunned myocardium in awake dogs.
- To determine if postischemic contractile dysfunction affects myocardial oxygen consumption and vasodilator reserve.
- To assess changes in coronary reactive hyperemia and adenosine-induced vasodilation.
Main Methods:
- Chronically instrumented awake dogs underwent sequential coronary artery occlusions.
- Left anterior descending coronary artery blood flow, pressures, and myocardial segment shortening were measured.
- Regional myocardial blood flow was quantified using microspheres; oxygen consumption and vasodilator reserve were determined.
Main Results:
- Sequential occlusions induced progressive myocardial stunning, reducing contractile function by 63%.
- Despite reduced function, coronary blood flow and myocardial oxygen consumption remained unchanged.
- Coronary vasodilator reserve was unaltered, but reactive hyperemia intensity and duration were decreased, while peak flow was preserved.
Conclusions:
- Postischemic myocardial contractile dysfunction in awake animals is not associated with reduced myocardial oxygen consumption.
- The relationship between coronary blood flow and oxygen utilization remains intact.
- While vasodilation to adenosine is normal, coronary reactive hyperemia is impaired in stunned myocardium.