Atrioventricular Optimization Improves Cardiac Resynchronization Response in Patients with Long Interventricular Electrical Delays: A Pooled Analysis of the SMART-AV and SMART-CRT Trials

Background The utility of atrioventricular (AV) optimization (AVO) algorithms remains in question. A substudy of the SMART-AV trial found patients with prolonged interventricular (RV-LV) delays ≥70 ms were more likely to benefit from CRT with AVO. The SMART-CRT trial evaluated AVO based on these results, but the study was underpowered. Objective To increase statistical power, data from SMART-AV patients meeting the inclusion criteria of RV-LV ≥70 ms were pooled with data from SMART-CRT to reassess AVO. Methods SMART-CRT and SMART-AV were prospective, randomized, multicenter clinical trials. Patients in both studies were randomized to be programmed with an AVO algorithm (SmartDelay) or fixed AV delay (120 ms). Paired echocardiograms obtained at baseline and six months were compared, with CRT response defined as ≥15% reduction in left ventricle end systolic volume (LVESV). Results A total of 451 complete patient datasets were pooled and analyzed. The baseline demographics between studies did not differ statistically in terms of age, sex, LV ejection fraction, or LVESV. The AVO group had a greater proportion of CRT responders (SmartDelay: 73.9%, Fixed: 63.1%, p=0.014) and greater changes in measures of reverse remodeling. SmartDelay patients with a recommended sensed AV delay outside the nominal range (100-120 ms) had 2.3 greater odds of CRT response than fixed AV delay patients. Conclusion Greater CRT response and measures of reverse remodeling were observed in patients with SmartDelay enabled versus a fixed AV delay. The present study supports the use of SmartDelay in patients with a CRT indication and interventricular delay ≥70 ms. Clinical Trial Registration ClinicalTrials.gov, NCT00677014 and NCT03089281