136-69: Incidence of Super-Response with Optimized Dual Site LV Cardiac Resynchronization Therapy

Purpose of the study: We studied the degree of echocardiographic response in 39 patients who participate in the Dual Site Left Ventricular Pacing study. Method used: Thirty-nine patients (23 male, mean LVEF 27 ± 10, normal sinus rhythm, left bundle branch block, 20 ischemic cardiomyopathy meeting standard cardiac resynchronization therapy (CRT) criteria, were randomized to single LV and RV vs. dual LV and RV CRT, and crossed over after 3 months to the other arm. Medications and AV intervals were carefully optimized. One LV lead was positioned mid or basal lateral, and the other anterior or posterior lateral closer to the apex. Maximal physical LV lead separation was attempted, requiring a positive fixation lead in 15 leads, retaining coronary venous stents in 12 veins, and coronary venoplasty in 4 veins. Echocardiograms performed at baseline, 3 months and 6 months were interpreted by a blinded echocardiographer. An increase in LVEF of >15% was considered response, >30% super-response, and normalization of LVEF hyper-response. Summary of results: There was a statistically significant 44.5% increase in LVEF at 3 months, and a further 7.5% increase at 6 months, in both groups combined. At 6 months, 31 patients (79.5%) had EF increase by >30%. Of these, 11 patients (28%) had LVEF normalize and 4 (10%) had EF increase >15% but <30%, for a total response rate of 90%. Five did not show an increase in EF. All 5 non-responders were male with ischemic cardiomyopathy. Conclusion: There was a large incidence of super- and hyper-response in this population compared to historical controls. The greatest response occurred after 3 months, but with further response at 6 months. Factors likely responsible for improvement include: medical/device optimization, painstaking lead positioning, and dual-site LV pacing.