Pulmonary Vascular Resistances among Heart Transplant Candidates: Are We Looking to the Right Player?

Abstract

Pulmonary vascular resistances (PVR) are among the key measurements derived from right heart catheterization (RHC) in the prognostic assessment of patients (pts) candidate to Heart Transplantation (HT). PVR however don't account for compliance and pulsatility of pulmonary circulation. Pulmonary arterial compliance (PAC) [stroke volume/pulmonary artery pulse pressure (SV/PAPP)], that is inversely related to PVR, and pulmonary effective arterial elastance (Ea) (sPAP/SV) incorporate compliance and pulsatility of right ventricular afterload. Both predict mortality and need for HT, but they have been studied only in conjunction with other parameters of pulmonary circulation. The aim of this study is to assess the prognostic role of parameters of resistive and pulsatile afterload of right ventricle (PAC, Ea and PVR) together with left ventricle filling pressures and comorbidities in pts referred for HT. All pts undergoing to a RHC between 2004-17 in our Center were included. Hemodynamic parameters and clinical variables were assessed at the first RHC. The primary endpoint was freedom from the combined incidence of death or need for urgent HT at 2 years. 401 pts (82%M, 53±10 yrs, 40.3% CAD, 10.7% on IABP) constituted study population; the incidence of the endpoint was 77.3±2.2%. Among hemodynamic variables, PAC, Ea, pulmonary artery wedge pressure (PAWP), cardiac output (as continuous variables) and PVR >3 WU predicted the endpoint at univariate analysis (p <0.05 for all); at multivariate analysis, only Ea retained statistical significance (HR: 1.02 per 1mmHg/ml increase, p=0.04). High Ea (>0.85 mmHg/ml, median value) predicted the endpoint (HR: 4.2, p=0.04) even after adjusting for clinical variables: GFR < 60 ml/min (HR:3.8), bilirubin > 1.2 mg/dl (HR:7.0), need for IABP (HR:32.6), all p<0.05. Of note, only 15% of pts with high PVRs had low Ea levels, compared to 67% in the low PVR group (p<0.01). A 1 mmHg reduction in PAWP led to an higher reduction in Ea in the group with PVR> 3 than in the group of lower PVR. The assessment of right ventricular afterload through evaluation of pulmonary artery elastance seems to better stratify than PVR the need of HT in patients with severe heart failure. Treatments directed to a reduction of PAWP can significantly modify elastance, especially in pts with high resistive afterload.