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Regional load dependence of postischemic myocardium
C W Buffington1, R J Coyle, S Watanabe
1Department of Anesthesiology, University of Pittsburgh, Pennsylvania.
Journal of Cardiac Surgery
|March 1, 1993
Summary
Myocardial contraction decreases after ischemia, with reduced response to preload. Inotropic stimulation partially restored function, but ideal post-ischemic treatment requires low afterload and high contractility.
Area of Science:
- Cardiology
- Physiology
Background:
- Limited research exists on how mechanical load impacts myocardial contraction post-ischemia.
- Understanding these effects is crucial for developing effective treatments for ischemic heart disease.
Purpose of the Study:
- To investigate the influence of preload and afterload on myocardial contraction following ischemia in a canine model.
- To assess the efficacy of inotropic stimulation in restoring cardiac function post-ischemia.
Main Methods:
- Developed a canine model to independently vary preload (left atrial pressure) and afterload (mean arterial pressure) at a constant heart rate.
- Measured systolic contraction and thickening under preischemic and postischemic conditions.
- Evaluated the effects of dobutamine on myocardial function post-ischemia.
Main Results:
- Preischemic systolic contraction increased proportionally with preload.
- Postischemic systolic contractions and response to preload were significantly diminished.
- Dobutamine partially restored systolic thickening but did not reach preischemic levels.
Conclusions:
- Myocardial ischemia markedly impairs contractility and the response to preload.
- Inotropic agents can partially improve function but do not fully reverse ischemic damage.
- Optimal management of postischemic myocardium involves managing mechanical load and contractility.