Impact of Mechanical Activation, Scar, and Electrical Timing on Cardiac Resynchronization Therapy Response and Clinical Outcomes

Abstract

Objectives Using cardiac magnetic resonance (CMR), we sought to evaluate the relative influences of mechanical, electrical, and scar properties at the left ventricular (LV) lead position (LVLP) on CRT response and clinical events. Background CMR cine displacement encoding with stimulated echoes (DENSE) provides high quality strain for overall dyssynchrony (circumferential uniformity ratio estimate [CURE, 0–1]) and timing of onset of circumferential contraction at the LVLP. CMR DENSE, late gadolinium enhancement, and electrical timing together could improve upon other imaging modalities for evaluating the optimal LVLP. Methods Patients had complete CMR studies and echocardiography before CRT. CRT response was defined as a 15% reduction in LV end-systolic volume. Electrical activation was assessed as the time from QRS-onset-to-LVLP-electrogram (QLV). Patients were then followed for clinical events. Results In 75 patients, multivariable logistic modeling accurately identified the 40 (53%) of patients with CRT response (AUC=0.95 [p<0.0001]) based on CURE (OR 2.59/0.1 decrease), delayed circumferential contraction onset at LVLP (OR 6.55), absent LVLP scar (OR 14.9), and QLV (OR 1.31/10 ms increase). The 33% of patients with CURE<0.70, absence of LVLP scar, and delayed LVLP contraction onset had a 100% response rate, whereas those with CURE≥0.70 had a 0% CRT response rate and a 12-fold increased risk of death, and the remaining patients had a mixed response profile. Conclusions Mechanical, electrical, and scar properties at the LVLP together with CMR mechanical dyssynchrony are strongly associated with echocardiographic CRT response and clinical events after CRT. Modeling these findings holds promise for improving CRT outcomes.

Cine dyscontractility index: A novel marker of mechanical dyssynchrony that predicts response to cardiac resynchronization therapy

“…We only had access to MRI data prior to CRT implantation-future studies that recruit patients undergoing MRI-conditional device implantation may be able to define changes in dyssynchrony and reverse remodeling of the LV after device implantation. Similarly, the impact of additional information about LV scar location on late gadolinium imaging 6 and/or the LV electrogram timings 8 should be assessed in future work. It is also possible that the index could be improved by further modifications; for example, some studies show that limiting an index calculation spatially to the septal region 24 or temporally to the ejection phase 25 improve predictive value.…”

“…While echocardiographic measures of dyssynchrony have only modest sensitivity and specificity for CRT response prediction in multicenter studies, 5 progress in cardiac magnetic resonance (MR) methods suggests that this modality may prove a more reliable predictor. [6][7][8] Dedicated MR sequences for quantitative assessment of motion include tagged MRI (tMRI) and displacement encoding with stimulated echoes (DENSE). While the strain indices derived by these methods have been used in the research setting, they have not gained wider clinical popularity.…”

Cardiac resynchronization therapy in patients with postero-lateral scar by cardiac magnetic resonance: A systematic review and meta-analysis

“…The 11 included reports [7][8][9][10][11][12][13][14][15][16][17] were all prospective single center studies. These studies enrolled a total of 666 patients who underwent CMR before CRT (the number of patients per study ranged between 12 and 209 patients with the median being 45) ( Table 1).…”

“…The definition below is inconsistent across the eight included studies [7,8,10,11,[13][14][15]17]. Significant scar pacing defined as either:…”

Accelerated Dynamic Cardiac MRI Using Motion-Guided Compressed Sensing with Regional Sparsity

“…Currently, tagged images using two-dimensional (2D) grid tags are typically acquired during a single breathhold (34), whereas common protocols for 2D cine DENSE typically require two separate breathholds, each with 1D displacement encoding (42).…”