An oversized allograft is associated with improved survival after lung transplantation for idiopathic pulmonary arterial hypertension

Abstract

Background: Idiopathic pulmonary arterial hypertension (IPAH) is associated with high short-term mortality after bilateral lung transplantation (BLT). Previous studies have suggested that oversized allografts are associated with improved outcomes and that this association was strongest within the first year after transplant. We hypothesized that oversizing the allograft is associated with improved survival after BLT for IPAH.

Methods: All adults in the United Network of Organ Sharing lung transplant registry who underwent first-time BLT for IPAH between October 1989 and April 2010 were studied. Lung size mismatch was assessed by calculating the predicted total lung capacity (pTLC) ratio of the donor to the recipient. The cohort was divided evenly into "undersized" (pTLC ratio less than the median pTLC ratio) and "oversized" (pTLC ratio exceeding the median pTLC ratio). Risk of death after BLT was analyzed using Kaplan-Meier survival and Cox proportional hazards models.

Results: The mean pTLC ratio was 0.93 ± 0.10 in the 302 undersized patients compared with 1.24 ± 0.14 in the 302 oversized patients. Cohorts had comparable baseline characteristics. Median survival was 831 days longer in the oversized cohort (2,166 vs. 1,335 days, p = 0.006). In a multivariate model controlling for sex mismatch, recipient factors, acuity, donor factors, and transplant factors, oversizing was associated with decreased hazard for death at 5 years (hazard ratio, 0.73; 95% CI 0.56-0.96, p = 0.02).

Conclusion: Oversizing the allograft is associated with improved survival after BLT for IPAH. In the setting of donor organ shortages and waiting list mortality, it is not practical to intentionally oversize the allograft. However, the pTLC ratio could provide further refinement in the peri-transplant risk assessment.

Keywords: idiopathic pulmonary arterial hypertension; lung size mismatch; lung transplant outcomes; lung transplantation; predicted total lung capacity.