Figure 1
The ascending aortic flow (A), pressure (B) and LV pressure (C) and the calculation of LV τe (D) in one normal rat. In (B), the red shaded area represents the aortic PTAs and the black line is the Pms. The start and end points of systole for PTAs calculation were identified as the intersection of 2 tangential lines around the foot of pressure waveform and that around the incisura caused by aortic valve closure, respectively. In (C), the red line represents the measured PLV and the green line is its derivative, i.e., dPLV/dt. In (D), the time course of LV isovolumic pressure decline is defined by the pressure point of the peak −dPLV/dt to 10 mmHg above the end-diastolic pressure. The LV τe was calculated as the negative inverse slope of the ln PLV versus t relationship. In this case, the LV τe was 8.84 ms with an r2 of 0.9980 and SEE of 0.42%. LV, left ventricular; PLV, LV pressure; Pms, mean systolic aortic pressure; PTAs, systolic aortic pressure-time area; r2, coefficient of determination; SEE, relative standard error of the estimate; τe, time constant of the LV isovolumic pressure decay.
