Hemodynamic forces from 4D flow magnetic resonance imaging predict left ventricular remodeling following cardiac resynchronization therapy

Abstract

Background: Patients with heart failure and left bundle branch block (LBBB) may receive cardiac resynchronization therapy (CRT), but current selection criteria are imprecise, and many patients have limited treatment response. Hemodynamic forces (HDF) have been suggested as a marker for CRT response. The aim of this study was therefore to investigate left ventricular (LV) HDF as a predictive marker for LV remodeling after CRT.

Methods: Patients with heart failure, EF < 35% and LBBB (n = 22) underwent CMR with 4D flow prior to CRT. LV HDF were computed in three directions using the Navier-Stokes equations, reported in median N [interquartile range], and the ratio of transverse/longitudinal HDF was calculated for systole and diastole. Transthoracic echocardiography was performed before and 6 months after CRT. Patients with end-systolic volume reduction ≥ 15% were defined as responders.

Results: Non-responders had smaller HDF than responders in the inferior-anterior direction in systole (0.06 [0.03] vs. 0.07 [0.03], p = 0.04), and in the apex-base direction in diastole (0.09 [0.02] vs. 0.1 [0.05], p = 0.047). Non-responders had larger diastolic HDF ratio compared to responders (0.89 vs. 0.67, p = 0.004). ROC analysis of diastolic HDF ratio for identifying CRT non-responders had AUC of 0.88 (p = 0.005) with sensitivity 57% and specificity 100% for ratio > 0.87. Intragroup comparison found higher HDF ratio in systole compared to diastole for responders (p = 0.003), but not for non-responders (p = 0.8).

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.

Keywords: Cardiac magnetic resonance; Device response; Heart failure with reduced ejection fraction; Left bundle branch block; Pacemaker.

Fig. 1

Pressure gradients, hemodynamic forces, and blood flow in a patient with heart failure and reduced ejection fraction. Left: The colored field illustrates the relative pressure gradients within the left ventricle at a single point in time. Local hemodynamic forces are illustrated with white arrows, with direction and magnitude indicated for each point. Center: The global force (white arrow) is the sum of all local forces and accelerates the blood flow (red arrow) towards the aorta during early systole. Right: By late systole, the global force is directed in the opposite direction of the flow, thereby decelerating the outflowing blood

Fig. 2

Study design and overview of workflow for hemodynamic force analysis. CMR, cardiovascular magnetic resonance; CRT, cardiac resynchronization therapy; ∆ESV, reduction in end-systolic volume; LBBB, left bundle branch block; TTE, transthoracic echocardiography

Fig. 3

Left ventricular hemodynamic forces over single cardiac cycle. In the apex-base direction, responders typically had a negative impulse at the beginning of systole (1), which is not seen as prominently in non-responders or controls. A subgroup of responders (n = 6) had a pattern with larger force amplitudes in diastole, with an early negative impulse and a late positive impulse (2 and 3). In the lateral wall-septum direction responders and non-responders had force patterns with a larger positive impulse in early diastole compared to controls (4 and 5). In the inferior-anterior direction, responders typically had larger amplitudes throughout the cardiac cycle compared to non-responders and controls

Fig. 4

Root mean square (RMS) left ventricular hemodynamic forces in responders (R, circles) and non-responders (NR, squares) to cardiac resynchronization therapy, and controls (CTL, triangles). Responders had significantly higher systolic HDF in the inferior-anterior direction, and significantly higher diastolic longitudinal (apex-base) HDF compared to non-responders

Fig. 5

Ratio of transversal to longitudinal hemodynamic forces during systole (left) and diastole (center) in responders (R, blue) and non-responders (NR, orange) to cardiac resynchronization therapy, and controls (CTL, green). Whiskers show range. Right: Receiver operating characteristic curve for ratio of transversal to longitudinal root mean square (RMS) forces in diastole. Dashed line of equality

Fig. 6

Paired comparison of transversal to longitudinal root mean square hemodynamic force ratio in responders (left) and non-responders (middle) to cardiac resynchronization therapy, and in controls (right)