Current perspectives modern hemodynamic evaluation of the pulmonary circulation. Application to pulmonary arterial hypertension and embolic pulmonary hypertension.

The hemodynamic evaluation of the pulmonary circulation normally includes the measurements of mean pulmonary artery pressure and a calculation of pulmonary vascular resistance (PVR). The definition of PVR can be improved by the measurements of pulmonary vascular pressures at several levels of flow to derive a pressure-flow line, and the site of PVR can be identified by the analysis of pulmonary artery pressure decay curves after balloon occlusion. An analysis of the morphology of pulmonary artery pressure and flow waves informs about right ventricular (RV) hydraulic load. As pulmonary hypertension is clinically a right heart failure syndrome, it is important to measure the coupling of RV to pulmonary arterial function. This can be done using a single beat method with sampling and synchronization of instantaneous pulmonary artery flow and RV pressure to calculate a ratio of end-systolic to arterial elastances. The optimal value of this ratio is depressed in minimally symptomatic pulmonary arterial hypertension patients, indicating pending right heart failure.