CMR Right Ventricular-Pulmonary Arterial Coupling and Right Ventricular Trabecular Complexity: Prognostic in Lung Transplant Assessment?

Abstract

Purpose Right ventricular (RV) function influences prognosis in pulmonary hypertension (PH), but key metrics are not clear. We assessed a cardiac magnetic resonance (CMR) index of RV-pulmonary arterial (PA) coupling as well as right ventricular (RV) trabecular complexity by its fractal dimension (FD), correlating to imaging indices and outcome. Methods Patients underwent CMR to assess biventricular volumes and systolic function. RV FD was assessed on CMR using custom-written code (FracAnalyse). RV-PA coupling was estimated by stroke volume (SV)/ RV end-systolic volume (ESV) ratio. Correlation between variables was assessed with the Pearson correlation test. Survival was analysed using the Cox proportional hazard ratio with the primary outcome of time to death. Results 78 patients were assessed for lung transplantation between 2013-2018, with a median follow up of 18.33 (interquartile range 17.25) months. 93% of the patients had underlying lung disease. 48 out of 62 patients had echo-detected PH (RV systolic pressure of > 35mmHg). Both SV/ESV and RV FD correlated to mean PA pressure (mPAP), RV ejection fraction (EF), indexed RV end-diastolic volumes (RVEDVi) and ESV (RVESVi), and right atrial (RA) area. On univariate analysis, survival was predicted by SV/ESV, RVEF, RVEDVi and RVESVi. Conclusion RV functional adaptation to afterload assessed by CMR predicts survival in patients referred for lung transplant assessment, on univariate analysis. Fractal analysis of RV trabecular complexity correlated with metrics influencing RV remodelling and contractility, but not survival.