Near-infrared Fluorescence Imaging During Ex Vivo Lung Perfusion: Noninvasive Real-Time Evaluation of Regional Lung Perfusion and Edema

Objective: Ex vivo lung perfusion (EVLP) is an excellent platform to evaluate donor lung function before transplantation, but novel methods are needed to accurately confirm transplant quality. Near-infrared fluorescence (NIRF) imaging with indocya-nine green (ICG) has been used in various clinical perioperative applications to eval-uate tissue perfusion. We used NIRF imaging during pig and human EVLP to evaluate donor lung perfusion and edema.Methods: Pig lungs with various degrees of lung injury (n = 10) and human lungs rejected from clinical transplantation (n = 3) were imaged during EVLP using intra-vascular ICG and a SPY Elite (Stryker) NIRF imaging unit. Optimal ICG and imaging conditions, and perfusion and edema quantification methods, were established. Pig lung transplants with extended graft preservation (n = 5) and control native lungs (n = 6) were also imaged.Results: A single ICG dose resulted in sustained donor lung NIRF throughout the EVLP. Even and homogenous ICG signal was demonstrated in areas of normal lung. Low NIRF was present in regions with poor tissue perfusion, and rapid, intense ICG accumulation occurred in damaged and edematous areas. Segmental perfusion defects were common in the peripheral and elevated regions of the lungs, and serial imaging showed gradual perfusion recovery during EVLP. Impaired microvascular reperfusion, indicated by a decreased NIRF ingress rate, was detected in trans-planted pig lungs early after reperfusion.Conclusions: NIRF imaging enables noninvasive real-time evaluation of lung perfu-sion and edema during EVLP. Prospective clinical studies are needed to determine the role of NIRF imaging in donor lung assessment and selection, and prediction of posttransplant outcomes. (J Thorac Cardiovasc Surg 2022;164:e185-203)