Impact of the New Pulmonary Hypertension Definition on Heart Transplant Outcomes: Expanding the Hemodynamic Risk Profile

Abstract

Background: At the recent 6th World Symposium on Pulmonary Hypertension (PH), the definition of PH was redefined to include lower pulmonary artery pressures in the setting of elevated pulmonary vascular resistance (PVR). However, the relevance of this change to subjects with PH due to left-heart disease as well as the preoperative assessment of heart transplant (HT) recipients is unknown.

Methods: The United Network for Organ Sharing database was queried to identify adult recipients who underwent primary HT from 1996 to 2015. Recipients were subdivided into those with mean pulmonary artery pressure (mPAP) < 25 mm Hg and ≥ 25 mm Hg. Exploratory univariable analysis was undertaken to identify candidate risk factors associated with 30-day and 1-year survival (conditional on 30-day survival) in recipients with mPAP < 25 mm Hg, and subsequently, parsimonious multivariable Cox proportional hazards models were constructed to assess the independent association with PVR.

Results: Over the study period, 32,465 patients underwent HT, including 12,257 (38%) with mPAP < 25 mm Hg. The median age was 55 years (interquartile range, 47-62) and the median PVR was 1.5 Wood units (WU) (interquartile range, 1-2.2) in recipients with mPAP < 25 mm Hg. After controlling for confounders, PVR was independently associated with increased risk for 30-day mortality (hazard ratio, 1.16; 95% CI, 1.05-1.27; P < .01), but not conditional 1-year mortality (hazard ratio, 1.03; 95% CI, 0.94-1.12; P = .55). PVR ≥ 3 WU was associated with an absolute 1.9% increase in 30-day mortality in those with mPAP < 25 mm Hg, a similar risk to recipients with PVR ≥ 3 WU and mPAP ≥ 25 mm Hg.

Conclusions: Elevated PVR remains associated with a significant increase in the hazard for 30-day mortality after cardiac transplantation, even in the setting of lower pulmonary artery pressures. These data support the validity of the new definition of pulmonary hypertension.

Keywords: heart failure; heart transplants; pulmonary circulation; pulmonary hypertension.