UC Irvine

Pulmonary vascular distensibility (α) is a marker of the ability of the pulmonary vasculature to dilate in response to increases in cardiac output, which protects the right ventricle from excessive increases in afterload. α measured with exercise predicts clinical outcomes in pulmonary hypertension (PH) and heart failure. In this study, we aim to determine if α measured with a passive leg raise (PLR) maneuver is comparable to α with exercise. Invasive cardiopulmonary exercise testing (iCPET) was performed with hemodynamics recorded at three stages: rest, PLR and peak exercise. Four hemodynamic phenotypes were identified (2019 ECS guidelines): pulmonary arterial hypertension (PAH) (n = 10), isolated post-capillary (Ipc-PH) (n = 18), combined pre-/post-capillary PH (Cpc-PH) (n = 15), and Control (no significant PH at rest and exercise) (n = 7). Measurements of mean pulmonary artery pressure, pulmonary artery wedge pressure, and cardiac output at each stage were used to calculate α. There was no statistical difference between α-exercise and α-PLR (0.87 ± 0.68 and 0.78 ± 0.47% per mmHg, respectively). The peak exercise- and PLR-based calculations of α among the four hemodynamic groups were: Ipc-PH = Ex: 0.94 ± 0.30, PLR: 1.00 ± 0.27% per mmHg; Cpc-PH = Ex: 0.51 ± 0.15, PLR: 0.47 ± 0.18% per mmHg; PAH = Ex: 0.39 ± 0.23, PLR: 0.34 ± 0.18% per mmHg; and the Control group: Ex: 2.13 ± 0.91, PLR: 1.45 ± 0.49% per mmHg. Patients with α ≥ 0.7% per mmHg had reduced cardiovascular death and hospital admissions at 12-month follow-up. In conclusion, α-PLR is feasible and may be equally predictive of clinical outcomes as α-exercise in patients who are unable to exercise or in programs lacking iCPET facilities.