Abstract
Background Delayed enhancement ( DE ) on magnetic resonance imaging is associated with ventricular arrhythmias, adverse events, and worse left ventricular mechanics. We investigated the impact of DE on cardiac resynchronization therapy ( CRT ) outcomes and the effect of CRT optimization. Methods and Results We studied 130 patients with ejection fraction ( EF ) ≤40% and QRS ≥120 ms, contrast cardiac magnetic resonance imaging, and both pre- and 1-year post- CRT echocardiograms. Sixty-three (48%) patients did not have routine optimization of CRT . The remaining patients were optimized for wavefront fusion by 12-lead ECG . The primary end point in this study was change in EF following CRT . To investigate the association between electrical dyssynchrony and EF outcomes, the standard deviation of activation times from body-surface mapping was calculated during native conduction and selected device settings in 52 of the optimized patients. Patients had no DE (n=45), midwall septal stripe (n=30), or scar (n=55). Patients without DE had better ∆ EF (13±10 versus 4±10 units; P<0.01). Optimized patients had greater ∆ EF in midwall stripe (2±9 versus 12±12 units; P=0.01) and scar (0±7 versus 5±10; P=0.04) groups, but not in the no- DE group. Patients without DE had greater native standard deviation of activation times ( P=0.03) and greater ∆standard deviation of activation times with standard programming ( P=0.01). Device optimization reduced standard deviation of activation times only in patients with DE ( P<0.01). Conclusions DE on magnetic resonance imaging is associated with worse EF outcomes following CRT . Device optimization is associated with improved EF and reduced electrical dyssynchrony in patients with DE .