Background: Cardiac resynchronization therapy (CRT) is less effective in patients with mildly wide QRS or non-left bundle branch block (non-LBBB). A new algorithm of every minute's optimization (adaptive CRT: ACRT algorithm) is effective in patients with CRT devices. This study investigated the clinical effect of the aCRT algorithm, especially in mildly wide QRS (120≤QRS<150 ms) or non- LBBB patients receiving CRT. Methods and Results: This study included 104 CRT patients (48 patients using the aCRT algorithm [adaptive group] and 56 patients not using the aCRT algorithm [non-adaptive group]). The primary endpoint was a composite clinical outcome of cardiac death and/or heart failure (HF) hospitalization. During a median follow-up of 700 days (interquartile range 362-1,173 days), aCRT reduced the risk of the clinical outcome, even in patients with mildly wide QRS or non-LBBB (log-rank P=0.0030 and P=0.0077, respectively) by Kaplan-Meier analysis. Use of the aCRT algorithm was an independent predictor of clinical outcomes in the multivariate analysis (hazard ratio (HR) 0.28, 95% confidence interval (CI): 0.096-0.78, P=0.015), the same as in patients with mildly wide QRS (HR 0.12, 95% CI: 0.006-0.69, P=0.015). Conclusions: The new aCRT algorithm was useful and significantly reduced the risk of the clinical outcome, even in patients with mildly wide QRS.
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