Transplant Size Mismatch in Restrictive Lung Disease.

Abstract

Purpose: To examine the effect of size mismatch on survival in lung transplant (LTx) patients with restrictive lung disease (RLD) using predicted total lung capacity (pTLC). Methods: All single (SOLT) and bilateral (BOLT) LTx for RLD from 1987-2011 in the United Network for Organ Sharing Database were identified. Pediatric, redo, and multi-organ LTx were excluded. Donor pTLC:Recipient pTLC, or pTLC ratio (pTLCr), quantified size mismatch. pTLCr was stratified as: <0.8, 0.8-0.9, 0.9-1.1, 1.1-1.2, and >1.2. A Cox proportional hazards model (CPH) evaluated the independent association of pTLCr with the hazard of death. To determine if there was a dramatic pTLCr critical point, a separate CPH using a linear spline model for pTLCr with 4 knots: 0.8, 0.9, 1.1, and 1.2, was used. Results: 3,532 SOLTs and 3,124 BOLTs for RLD were identified. Median pTLCr for SOLT and BOLT was 1.0 (range 0.69-1.47) and 0.98 (range 0.66-1.45) respectively. pTLCr examined as a categorical variable revealed that undersizing (pTLCr<0.8) for SOLT and moderate oversizing (pTLCr=1.1-1.2) for SOLT and BOLT had a harmful survival effect (Table). CPH with linear spline analysis revealed significant changes in SOLT mortality by variation of pTLCr between 0.8-0.9 and between 1.1-1.2. No specific spline was identified for BOLT (Figure). Conclusions: Patients with RLD who receive a SOLT appear susceptible to the detriments of an undersized or oversized lung based on pTLCr, particularly a pTLCr between 0.8-0.9 and 1.1-1.2. Patients with RLD receiving a BOLT appear at a higher mortality risk with a pTLCr between 1.1-1.2, though no clear spline was identified. Additional information on respiratory mechanics and other mortality risk factors could be incorporated to better define the importance of size mismatch.Table: No Caption available.Figure: No Caption available.