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Medical Definition of Transmural pressure
1. Pressure across the wall of a cardiac chamber or of a blood vessel. In the heart, transmural pressure is the resultant of the intracavitary pressure minus the extracavitary (i.e., pericardial) pressure and is the distending, i.e., true filling, pressure of the cardiac chamber of measurement when this is done during diastole. Since the pericardial pressure normally approximates zero, the filling pressure (usually equal to ventricular diastolic mean pressure), obviating the complexities of measuring pericardial pressure. (05 Mar 2000)