Effect of Targeting Left Ventricular Lead Position on the Rate of Response to Cardiac Resynchronization Therapy.

Background. Identifying \& optimizing strategies to reduce the burden of heart failure (HF) is vital. Despite advances in pharmacotherapy, patients with HF are at high risk for death \& hospitalization. Over 25% of patients with systolic HF have dyssynchronous ventricular contraction that results in paradoxical septal motion, further impairing left ventricular (LV) function \& HF progression. Cardiac resynchronization therapy (CRT) synchronizes ventricular mechanical activity, improves cardiac output \& reduces HF symptoms. However, \~50% of patients do not clearly respond to CRT. Sub-optimal placement of the LV pacing lead appears to be an important reason for non-response. Screening. Mechanical synchrony is vitally important in optimizing CRT response. Patients will be pre-screened with echocardiograms (echo) \& CRT provided to only those with dyssynchrony. The predicted rate of CRT response in patients pre-screened for dyssynchrony is estimated at 65%. CRT response. The combined use of a valid \& simple measure of functional capacity with a reproducible measure of LV volume is optimal in identifying CRT responders. These outcomes will be assessed using the Specific Activity Scale \& radionuclide angiography (RNA), respectively. Primary hypothesis. Targeted LV lead placement will result in an increased probability of CRT response at 52 weeks vs. usual (lateral wall) lead placement. CRT response will be defined as ≥ 10% relative reduction in LV end systolic volume \& ≥ 1 Specific Activity Scale class improvement.