139 Right ventricular diastolic function in acute pulmonary embolism

Abstract

Background: The effects of acute pulmonary embolism (PE) on right ventricular (RV) diastolic function may be one of the determinants of right heart failure. We analysed the parameters of RV diastolic function in a porcine model of PE by the use of phase plane (PP) analysis. In the PP method, a periodic function is plotted such that the function, RV pressure (P), is the abscissa and its time derivative (dP/dt) is the ordinate. Methods: In six anaesthetised open chest pigs, RV pressure-volume (PV) loops were obtained by the conductance catheter technique. Measurements were realised in basal conditions, and repeated 1 hour after injection of coagulated autologous blood clots (0.3g/kg) in the superior vena cava. PV loops and PP loops were constructed with pressure and volume signals. The parameters of RV diastolic function were calculated from the PV and PP loops. Results: End-diastolic pressure and end-diastolic volume increased respectively from 3.40 ± 2.71 to 6.46 ± 2.36 mmHg (mean ± SD, p < 0.05) and from 60.73 ± 9.65 to 80.45 ± 3.72 ml (mean ± SD, p < 0.05), with no significant change in RV compliance (0,19 ±0.14 and 0.19 ± 0.10 ml/mmHg, mean ± SD). RV peak negative dP/dt extended from 0.39 ± 0.08 to 0.65 ± 0.01 mmHg/msec (mean ± SD, p < 0.01). Monoexponential decay time constant (Tau) did not show significant variation (37.85 ± 6.90 to 41.22 ± 13.98 msec, mean ± SD). The RV relaxation curve in the PP graph was nonlinear and was fitted with a quadratic function (dP/dt = A P2+B P+ dP/dt°). The curvilinearity coefficient (A) and the intercept (dP/dt°) did not change significantly but the second constant (B) significantly decreased from -40.30 ± 13.50 to -56.72 ± 11.60 sec-1 (mean ± SD, p < 0.01). Conclusions: As assessed by PP analysis, acute RV pressure overload by PE induces modifications in RV diastolic function. The right ventricle dilates and its diastolic filling pressure increases. Relaxation time constant calculated with monoexponential decay method, that considers linear relaxation of the ventricle, does not significantly changed. The relaxation curve in the PP graph, however, appears modified, as shown by the higher second constant of the fitted quadratic function. This reflects that the relaxation is non-uniform and that the non-uniformity is modified in acute PE in a such way that Tau would increase in early relaxation while it would decrease in late relaxation.