pressure across the wall of a cardiac chamber or of a blood vessel. In the heart, transmural pressure is the result 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. Given that the pericardial pressure normally approximates zero, the filling pressure usually equals ventricular diastolic mean pressure, obviating the complexities of measuring pericardial pressure.