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Abstract:
Analysis of the in situ heart performance has been guided by the concepts of pump and muscle mechanics derived from studies on isolated heart and papillary muscle, respectively. It is occasionally beneficial to evaluate the cardiac performance separately on heart as a pump or as a muscle. Cardiac output is determined by the interaction among preload, afterload and contractility. Thus, it is sometimes difficult to estimate the contractile state of the diseased heart simply from hemodynamic measurements. Therefore, it is necessary to compare hemodynamics between rest and stress states or to apply concepts of "afterload mismatch and preload reserve" as well as end-systolic pressure volume relations in quantitative evaluation of the cardiac performance. Regional wall motion measurements are also useful to detect regional myocardial ischemia.