Cardiac energetics using virtual instrumentation: processing pressure-volume diagrams

A virtual instrument was developed using LabView® for analysis of the cardiovascular energetics to supplement a system of left ventricular function analysis. It calculates stroke work (SW), cardiac efficiency (η) and myocardial oxygen consumption (mVO₂). It uses intraventricular pressure and volume signals in normal conditions and during acute preload reduction to determine the Suga-Sagawa straight line (ESPVR). The end diastolic pressure-volume relationship (EDPVR) was constructed using an exponential fitting of the real pressure-volume data. Some details to optimize area calculations are also summarized. Calculated SW using this virtual instrument did not have significant differences against the same parameter calculated with high precision mathematical software in identical PV loops, while the efficiency η yielded an error of +(8.2 ± 1.6)%. As for the accuracy in the area determinations, it is concluded that this virtual instrument constitutes a reliable and simple predictor of the cardiac energetics.