Hemodynamic Forces from 4D Flow Magnetic Resonance Imaging for Optimised Prediction of Cardiac Resynchronisation Therapy Outcome

Background Patients with heart failure and left bundle branch block (LBBB) may receive cardiac resynchronisation therapy (CRT), but many patients have limited treatment response (1). The use of imaging to optimise patient selection has been repeatedly attempted with some success (2), and scar detected on late gadolinium enhancement (LGE) imaging has been associated with reduced response rates (3). Intraventricular hemodynamic force (HDF) analysis has been suggested as a novel marker for assessment of patients eligible for CRT (4). The aim of this study was therefore to investigate if septal scar from LGE or left ventricular HDF computed from cardiac magnetic resonance (CMR) imaging can improve prediction of CRT outcome. Methods Patients with heart failure, EF<35% and LBBB (n=22) underwent CMR with 4D flow at 1.5T or 3T (Achieva, Philips Healthcare) prior to CRT (Figure 1). Scar was assessed by LGE. Left ventricular HDF were computed based on the Navier-Stokes equations, using a validated module in the software Segment v3.3 R10057 (Medviso, Lund, Sweden) (5). Forces (N) were analysed in three orthogonal directions as root mean square (RMS) and peak values, reported in median [interquartile range]. Transversal/longitudinal HDF ratio was calculated for systole and diastole. Echocardiography was performed before and six months after CRT, and patients with end-systolic volume reduction ≥15% at follow-up were defined as responders. The Mann-Whitney U test was used for group comparisons, Fisher’s exact test for binary categorical data, Wilcoxon test for paired comparisons, and receiver operating characteristic analysis for prediction of CRT response. Results There was no difference between responders and non-responders in LGE (Table 1). Non-responders had smaller HDF than responders in the inferior-anterior direction in systole (RMS: 0.055 [0.027] vs 0.070 [0.032], p=0.04; peak: 0.11 [0.069] vs 0.15 [0.083], p=0.03), and in the apex-base direction in diastole (RMS: 0.087 [0.018] vs 0.11 [0.046], p=0.047). Non-responders had larger diastolic HDF ratio than responders (RMS: 0.89 [0.45] vs 0.67 [0.20], p=0.004; peak: 1.1 [0.51] vs 0.57 [0.40], p=0.01) (Figure 1). Receiver operating characteristic analysis of diastolic HDF ratio found an area under the curve of 0.88 (p=0.005). Identification of non-responders using diastolic HDF ratio with a specificity of 100%, resulted in a ratio of >0.87 for non-responders, with a sensitivity of 57%. Intragroup comparison found higher HDF ratio in systole than diastole for responders but not for non-responders (Figure 1). Conclusions Prediction of left ventricular remodelling following CRT may be optimized by hemodynamic force analysis from 4D flow CMR, while septal scar from LGE was not found indicative of CRT outcome in this pilot study. Larger-scale studies are required before clinical implementation of HDF analysis.Table 1Figure 1