Fig. 5. Transpulmonary hysteresis measures pulmonary vascular compliance and predicts right heart tolerance.

Shown is an example of (A) a hysteretic transpulmonary relationship between mean pulmonary artery pressure (mPAP) and left ventricular end-diastolic pressure (LVEDP) across the respiratory cycle in one animal with constant pVAD support at a steady physiological state. A corresponding example of (B) a nonhysteretic transsystemic relationship between mean arterial pressure and right ventricular end-diastolic pressure is similarly shown for one animal with constant pVAD support at steady state. (C) The relationship between pulmonary vascular compliance and area of the transpulmonary hysteresis loops is shown for the spectrum of states modeled in the five animals with pVAD support. N = 23 states modeled, P < 0.001. (D) The resulting correlation between right ventricular stroke work, representing right heart tolerance to pVAD support, and the percent change in transpulmonary loop area across pVAD speed sweeps is presented across the range states modeled in all animals. N = 21 complete pVAD speed sweeps, P < 0.0001. Linear regression was performed to confirm validity of trends. Corresponding curves and the square of the multiple correlation coefficient are denoted for correlations of statistical significance, determined by P value < 0.05.