1349194 - Hemodynamic forces predict left ventricular remodeling following cardiac resynchronization therapy in heart failure with left bundle branch block

Patients with heart failure and left bundle branch block (LBBB) may benefit from cardiac resynchronization therapy (CRT), but current selection criteria are imprecise and many patients have limited treatment response (1). The use of imaging to improve prediction of CRT response has been repeatedly attempted with some success (2), however not yet gained wide acceptance. Hemodynamic force (HDF) analysis of ventricular blood flow is a novel marker of cardiac function, suggested to convey unique information about the coupling between ventricular motion and the resulting blood flow patterns (3). The aim of this study was therefore to investigate left ventricular HDF computed from cardiac magnetic resonance (CMR) imaging as a marker for CRT treatment response.

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). Viability was assessed by late gadolinium enhancement imaging. Left ventricular HDF were computed based on the Navier-Stokes equations, using a previously validated module in the software Segment v3.3 R10057 (Medviso, Lund, Sweden) (4). Measurements were analyzed in three orthogonal intraventricular directions, and reported as root mean square values in median [interquartile range]. The ratio of transversal to longitudinal HDF 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. For reference values, we analyzed HDF in eight healthy subjects matched for sex and age at the group level. 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 (ROC) analysis for prediction of CRT response.

Results:

At follow-up 6 ± 2 months post CRT, 15 patients were classified as responders and 7 as non-responders. Non-responders had smaller HDF than responders in the inferior-anterior direction in systole (0.055 [0.027] vs 0.070 [0.032], p=0.04), and in the apex-base direction in diastole (0.087 [0.018] vs 0.11 [0.046], p=0.047). Non-responders had larger diastolic HDF ratio than responders (0.89 [0.45] vs 0.67 [0.20], p=0.004) (Figure 2). 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 (p=0.003) and controls (p=0.008), but not for non-responders (p=0.8) (Figure 2).

Conclusion:

Hemodynamic force ratio is a potential marker for identifying patients with heart failure and LBBB who are unlikely to benefit from CRT. Larger-scale studies are required before implementation of HDF analysis into clinical practice.