Prognostic Implications of Abnormal Left-Right Lung Perfusion Differential on Routine Post-Transplant Ventilation-Perfusion Scans

Abstract

<h3>Purpose</h3> Lung ventilation-perfusion (VQ) scans can be used to diagnose pulmonary thromboembolic disease as well as for surgical planning and monitoring after lung transplant, but the long-term implications of abnormalities on routine post-transplant studies are unknown. The relative lung perfusion distribution obtained from VQ scans estimates pulmonary blood flow, with up to a 10% difference (55%-45% right-to-left) considered normal. We hypothesized that unbalanced lung perfusion on 3-months post-transplant VQ scans would be associated with poorer long-term survival and increased frequency or severity of chronic lung allograft (CLAD) and baseline lung allograft dysfunction (BLAD). <h3>Methods</h3> We studied routine 3 month VQ scans from double lung transplant recipients in our program between 2004-2016. Abnormal perfusion differential was deemed ≥10%. We used Kaplan Meier estimation with log rank tests to assess the association with survival as well as CLAD onset and Fisher's Exact test and Cochran-Armitage trend testing to test the relationship to baseline lung allograft dysfunction. <h3>Results</h3> Of 340 patients who met inclusion criteria, 169 (49%) had a relative perfusion differential of at least 10% on their 3-months VQ scans. Patients with increased perfusion differential had longer hospital stays (24 days vs. 21 days; p=0.004), poorer overall survival (Figure 1, p=0.011) and increased CLAD onset (p=0.012). Increased perfusion differential was also associated with increased risk of BLAD (42% vs. 32%; p=0.043) and higher grade BLAD (p=0.006). <h3>Conclusion</h3> Abnormal relative lung perfusion differential is common after lung transplant and associated with increased risk of death, poor post-transplant baseline function and CLAD onset. This measurement warrants further exploration as a potential predictor of future lung dysfunction and related risk.