Left ventricular lead position, mechanical activation, and myocardial scar in relation to left ventricular reverse remodeling and clinical outcomes after cardiac resynchronization therapy: a feature-tracking and contrast-enhanced cardiovascular magnetic resonance study

Background: Late mechanical activation (LMA) and viability in the left ventricular (LV) myocardium have been proposed as targets for LV pacing during cardiac resynchronization therapy (CRT). Objective: The purpose of this study was to determine whether an LV lead position over segments with LMA and no scar improves LV reverse remodeling (LVRR) and clinical outcomes after CRT. Methods: Feature-tracking and late gadolinium enhancement images were analyzed retrospectively in patients with heart failure (HF) (n = 89; mean age 66.8 ± 10.8 years; LV ejection fraction = 23.1% ± 9.9%) who underwent cardiovascular magnetic resonance (CMR) scanning before CRT implantation. Lead positions were classified as concordant (no scar and LMA [time to peak systolic circumferential strain]) or nonconcordant (scar and/or no LMA). Results: LVRR occurred in 68% and 24% of patients with concordant and nonconcordant LV lead positions, respectively (P <.001). Over a median of 4.4 years (range 0.1-8.7 years), LV lead concordance predicted cardiac mortality (adjusted odds ratio [aOR] 0.27; 95% confidence interval [CI] 0.12-0.62) and cardiac mortality or HF hospitalizations (aOR 0.26, 95% CI 0.12-0.58). "No scar" in the paced segment predicted cardiac mortality (aOR 0.24; 95% CI 0.11-0.52) and cardiac mortality or HF hospitalizations (adjusted aOR 0.24; 95% CI 0.12-0.49). Conclusion: LV lead deployment over nonscarred LMA segments was associated with better LVRR and clinical outcomes after CRT. LVRR was primarily related to LMA, whereas events were primarily related to scar. These findings support the use of late gadolinium enhancement CMR and feature-tracking CMR in guiding LV lead deployment.