Cardiac Oxygen Consumption and Hemodynamics
Cardiac oxygen consumption can be determined from the product of coronary flow and arterio-venous oxygen content difference. To circumvent these preferentially simultaneous but difficult determinations, many indices for estimating oxygen consumption from mechanical variables have been proposed. Heart rate is a primary determinant of oxygen consumption. The second major determinant is tension (stress) generation of the cardiac muscle, mostly measured as ventricular pressure. The most used methods are the (Heart-)Rate Pressure Product (RPP), often used in biochemical studies, and the Tension Time Index (area under pressure during ejection, TTI). Total oxygen consumption depends on ‘unloaded’ contraction, i.e., ‘cell maintenance’, plus excitation-contraction coupling (Ees, the slope of the End-Systolic Pressure-Volume relation), and the Pressure-Volume Area (PVA) that is the sum of external work plus potential energy measurable from the Pressure-Volume Relation.
KeywordsCardiac oxygen consumption Rate pressure product Tension time index Pressure-volume area Potential energy
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