Actual Size Mismatch in Lung Transplantation for Restrictive Lung Disease

Abstract

<h3>Purpose</h3> Donor to recipient <i>predicted</i> total lung capacity (TLC) ratio is increasingly used for size matching in lung transplantation. This can overlook significant reductions in the <i>actual</i> TLC frequently seen in restrictive lung diseases. Forced vital capacity (FVC) is a useful surrogate for actual TLC, with proportionate decreases with progression of restrictive conditions. Analyzing donor predicted:recipient actual FVC could better predict actual lung size mismatch. <h3>Methods</h3> The UNOS database was used to identify 7,572 patients with restrictive lung disease undergoing isolated bilateral lung transplantation from 2005 to 2021. Lung size mismatch was quantified by donor:recipient FVC ratio, and patients were divided into quintiles. Multivariable cox regression was used to assess the relationship between size mismatch and all-cause mortality, adjusting for patient, donor and center baseline characteristics including lung allocation score (LAS) and degree of recipient FVC decline. Restricted cubic splines were used to assess the non-linear relationship between the FVC ratio and relative mortality hazard. Median follow-up was 2.6 (range 0-15) years. <h3>Results</h3> The median age of the cohort was 59 (Interquartile range (IQR) 53-64) years, 32.5% (n=2,464) were female and the median LAS was 47.1 (IQR 39.7-67.3). The median FVC ratio was 2.4 (range 1.1-5.3). Overall unadjusted 10-year survival was 37.3% (95% confidence interval (CI) 35.5-39.2). The primary cause of death was graft failure in 19.0% (n=532) cases. The highest quintile of FVC ratio was an independent predictor of mortality in multivariable analysis (hazard ratio 1.2, 95% CI 1.1-1.4). Spline analysis indicated that an FVC ratio >3.45 predicted significantly worse survival (Figure 1), corresponding to the 1,043 (14%) most oversized patients. <h3>Conclusion</h3> Oversizing with respect to FVC results in worse long-term survival despite adjustment for baseline characteristics, emphasizing the importance of considering recipient actual TLC in donor-recipient matching.