15\u2005Cardiac magnetic resonance (CMR) assessment of right ventricular-pulmonary arterial coupling and right ventricular trabecular complexity: impact on prognosis in patients undergoing lung transplant assessment

Abstract

Introduction Right ventricular (RV) function strongly influences prognosis in pulmonary hypertension (PH), but it remains unclear what key metrics are most clinically relevant. The purpose of this study was to assess the clinical relevance of both RV trabecular complexity and adequacy of RV functional adaptation to increased afterload as assessed by CMR in patients undergoing lung transplant assessment. Methods Between 2013 and 2018, 84 consecutive patients underwent lung transplant assessment with echocardiography and CMR (1.5T - Siemens Aera) to assess biventricular volumes and function as well as late gadolinium enhancement (LGE). RV trabecular complexity was assessed by its fractal dimension (FD) on CMR, using freely available code (FracAnalyse). RV functional adaptation to increased afterload was assessed with the RV-pulmonary arterial (PA) coupling index (stroke volume(SV)/end-systolic volume(ESV) ratio). Survival was analyzed using the Cox proportional hazard ratio with the primary outcome of time to death. Results In total 84 patients (median age 53±16 years, 54% male) were included in analysis. Median follow up period was 19.3±17.2 months. Underlying lung disease was recorded in 98% of the study population. Tricuspid regurgitation was echo-detected in 66 patients; 77% (51pts) had echo-calculated pulmonary hypertension (PH) with an estimated RV systolic pressure >35\u2009mmHg and estimated mean PA pressure of 30±10\u2009mmHg. 78.4%, 15.7%, and 5.9% of PH patients were categorized to Groups 3, 5 and 1 of WHO PH classification respectively. Mean LV and RV ejection fraction were 62%±1.07% and 51%±18% respectively. Both SV/ESV and RV FD correlated to mPAP, CMR-derived right atrial area, RVEDVi and RVESVi (table 1). RV FD did not differ significantly in patients with PH. Survival was predicted by SV/ESV ratio, RVEF, indexed RV end-diastolic volume (EDVi), RV end-systolic volume (ESVi), and mPAP on univariate analysis (table 1; SV/ESV carried a hazard ratio of 0.12, p<0.005). Conclusions In patients with underlying lung disease referred for lung transplant assessment, RV functional adaptation to afterload assessed by CMR seems to predict survival. Fractal analysis of RV trabecular complexity correlated with metrics influencing RV remodelling and contractility, although not survival. Assessment in a larger cohort is required to determine utility of these metrics.Abstract 15 Table 1 CMR and echo variables, correlations and outcomes in patients undergoing lung transplant assessment All patients (n =84 ) Alive (n= 70) Dead (n= 14) Alive vs dead p value HR CI p value Mean/ median SEM/IQR Mean/median SEM/IQR Mean/median SEM/IQR Demographics Age (years) 53 16 53 15 50 18 0,26 Gender (M) 46 37 9 0,43 BSA 1,78 0,02 1,78 0,03 1,79 0,05 0,84 Ethnicity overall 0.90 White 72 60 12 African 2 2 0 Afro-Caribbean 6 5 1 Asian 4 3 1 Diagnosis Underlying lung disease overall 0.46 ILD 28 23 5 Emphysema 32 27 5 Cystic Fibrosis 15 14 1 Bronchiectasis 5 3 2 Other 3 2 1 Pulmonary hypertension (echo diagnosis, n =51 ) 51 41 10 0,58 Clinical classification of patients with PH (n =51 ) overall 0.64 Group 1 3 3 0 Group 3 40 32 8 Group 5 8 6 2 Transplanted 22 15 7 0,03 2,06 0.68–6.22 0,20 MRI and Echo indices mPAP 27 11 26 10 33 23 0,04 1,05 1.01–1.09 <0.005 CMR LVEDVI 58 23 59 24 57 19 0,93 CMR LVESVI 22 13 21 13 25 13 0,30 CMR LV StVI 38 1,54 37 1,43 39 6,04 0,63 CMR LVEF 62 1,07 63 1,14 58 2,77 0,06 CMR RVEDVI 72 32 70 28 83 62 0,01 1,03 1.01–1.04 <0.005 CMR RVESVI 41 2,62 37 2,06 64 10,14 0,02 1,03 1.01–1.04 <0.005 CMR RV StVI 37 14 37 13 35 11 0,49 CMR RVEF 51 18 53 15 38 17 ,001 0,94 0.90–0.97 <0.005 CMR 4ch RAArea 16 7 16 6 20 6 0,11 LGE 14 9 5 0,04 2,45 0.79–7.61 0,12 Non-insertion point LGE 7 5 2 0,38 RV-PA coupling SV/ESV 1,03 0,72 1,12 0,67 0,57 0,48 ,001 0,12 0.027–0.52 <0.005 Global FD 1,26 ,004 1,26 ,004 1,26 ,012 0,49 Maximal Basal FD 1,33 ,007 1,32 ,008 1,33 ,017 0,35 Mean Basal FD 1,26 ,006 1,25 ,007 1,28 ,014 0,06 Maximal Apical FD 1,30 ,007 1,30 ,008 1,30 ,016 0,74 Mean Apical FD 1,25 ,007 1,25 ,007 1,25 ,016 0,80 Correlations RV EDVI RV ESVI RV SVI RV EF RA area mPAP SV/ESV r value −0,407 −0,712 0250 0847 −0,231 −0,301 p value <0.001 <0.001 ,022 <0.001 ,042 ,014 Global FD r value ,319 ,303 ,130 -,203 ,280 ,290 p value <0.005 ,005 ,238 ,064 ,013 ,018 Maximal Basal FD r value ,389 ,350 ,226 -,196 ,296 ,267 p value <0.001 <0.005 ,039 ,073 ,008 ,030 Mean Basal FD r value ,401 ,373 ,179 -,215 ,350 ,297 p value <0.001 <0.001 ,102 ,050 <0.005 ,016 BSA: body surface area; ILD: Interstitial lung disease; LVEDVi or RVEDVi: indexed left ventricular or right ventricular end-diastolic volume; LVESVi or RVESVi: indexed LV or RV end systolic volume; LV StVI or RV StVI: indexed LV or RV stroke volume; LVEF or RVEF: LV or RV ejection fraction; LGE: late gadolinium enhancement; FD: fractal dimension; HR: hazard ratio; CI: confidence interval, SEM/IQR: standard error of mean/interquartile\u2009range)