Effects of CRT Optimization as Assessed by Cardiac MR

This is a prospective, randomized study designed to evaluate if CRT device optimization, guided by electrocardiography, improves cardiac function and clinical outcomes among patients considered non-responders to CRT. All patients will have electrocardiographic assessment of electrical dyssynchrony at a range of device settings using standard ECG machines. All patients will then have a baseline CMR study at baseline CRT programming, underlying rhythm, and optimal settings derived from the electrocardiographic assessment to assess acute effects of CRT optimization on mechanical synchrony, LV regional wall motion, and LV structure/ function. To assess chronic effects of CRT optimization, patients will be randomized in a 1:1 ratio after baseline CMR to either the active comparator arm (baseline CRT programming), or the experimental arm (CRT device programmed to optimal settings derived from the electrocardiographic assessment). Patients will be blinded to randomization. After 6 month, all patients will return for follow up CMR study to assess chronic effects. After follow up CMR imaging, the active comparator group will crossover to the experimental group. After 12 months, all patients will return for follow up echocardiogram to further evaluate the chronic effects of CRT optimization.