S2 Evaluation of lung transplant function and detection of CLAD using 129Xe-MRI and LCI

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Introduction Outcomes after LTx are limited by development of Chronic Lung Allograft Dysfunction (CLAD), defined spirometrically as an FEV1 <80% best post-transplant (ISHLT criteria). Lung clearance Index (LCI) is sensitive to early small airway disease. Hyperpolarised-MRI using 129Xe (HPMRI) enables functional imaging of lung disease and is more sensitive than LCI in other conditions, but has limited available literature on detection of CLAD in LTx recipients. Methods Participants were recruited up to 6 years post-LTx and were CLAD-free at time of study entry. LCI and FEV1 were measured at routine serial clinic visits in clinically stable double/heart-lung transplant recipients. MRI was measured within 4 weeks of lung function. Ventilation defect percentage (VDP) and ventilation heterogeneity index (VHI) were calculated from HPMRI. Results 14 patients were assessed with both MRI and LCI: 6F; mean (SD) age 49.8 (12.0); time since transplant 1.9(1.8) years [range 0.46–5.59]. Median (IQR) LCI was 8.2 (7.8–9.1), 13 (93%) were higher than ULN (of 6.8); FEV1%baseline was 90.7 (83.5–95.9). Median (IQR) time between scan and lung function was -5 days (-15.3–6.0). Median (IQR) VDP was 2.6 (1.4–8.9), above ULN (of 2%) in 8 (57%). Median VHI was 8.9.Ventilation defects were widely distributed with no lobar patterns. There were significant correlations between both lung function (LCI and FEV1) and imaging parameters (VHI and VDP), p<0.05. Two patients had CLAD at time of MRI, with FEV1 of 71% and 40% baseline. Both had elevated LCI (12.5, 11.9 respectively) as well as elevated VDP (42.3, 20.7) and VHI (18.8, 16.6) Conclusions HP-MRI can be used to identify ventilation defects in LTx patients. Measures of VDP and VHI correlate well with both FEV1 (%baseline) and LCI. Majority of LTx patients have abnormalities in ventilation imaging (VDP, VHI) or physiology (LCI) even when post-transplant FEV1 is preserved. Longitudinal data are needed to establish if indices derived from HPMRI and LCI precede sustained drops in FEV1, to aid earlier detection of CLAD.

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