Twelve‐Lead ECG Optimization of Cardiac Resynchronization Therapy in Patients With and Without Delayed Enhancement on Cardiac Magnetic Resonance Imaging

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.