Abstract 17077: Pulmonary Artery Compliance: Resistance is (Not?) Futile

Introduction: Small studies have suggested that low pulmonary artery compliance (PAC) — quantified by dividing stroke volume by the pulmonary artery pulse pressure — is an early indicator of pulmonary hypertension (PH). However, the relationship between PAC and mortality, and the clinical utility of PAC in all-comers remains in question. Research Questions: How does the risk of mortality in all-comers change with PAC? Does the PAC provide prognostic information over established hemodynamics (i.e., pulmonary vascular resistance [PVR], mean pulmonary artery pressure [mPAP])?

Methods: Analysis was conducted on adult patients undergoing right heart catheterization at the University of Pittsburgh Medical Center Presbyterian Hospital 2005 - 2020, excluding those with prior heart/lung transplant, ventricular assist devices, and missing/non-physiologic hemodynamics. A cubic spline model was constructed to describe the relationship between PAC and the predicted risk of death. Multivariable Cox models for mortality were compared by plotting the distribution of 100 Harrell’s Concordance indices derived from Monte Carlo cross-validation. The fully-adjusted model was compared to models with one variable removed, thereby assessing the relative contribution of the withdrawn variable to model performance.

Results: The cohort included 12,948 patients (median age 64, 55% male, 84% White); 29% had combined post- and pre-capillary PH, 24% pre-capillary PH, and 17% isolated post-capillary PH. The predicted risk of mortality 1) increased linearly as PAC decreased below 3 mL/mmHg, 2) tapered for PACs between 3 - 5 mL/mmHg, and 3) remained constant at PACs above 5 mL/mmHg (Figure 1). Removal of PAC from Cox models predicting mortality did not substantially affect model performance (Figure 2).

Conclusions: A PAC below 5 mL/mmHg, and especially below 3 mL/mmHg, is associated with increased mortality; however, PAC does not improve prognostic information over the mPAP and PVR.