Tailoring of the AV interval during left bundle branch pacing. Playing with fusion: a new approach beyond out-of-the-box programming

Background Optimization of biventricular pacing for cardiac resynchronization therapy with fusion (fusion-optimized intervals method) has been shown to result in better left ventricular remodeling. However, information regarding the programming of the auriculoventricular (AV) interval during left bundle branch pacing (LBBP) is scarce. Purpose Assess with ECG imaging the electrical benefit of optimization of the AV interval during LBBP. Methods Retrospective analysis of prospectively collected data. Pilot study including 10 patients who received LBBP with resynchronization therapy indication and had normal AV conduction, sinus rhythm, and left bundle branch block in the context of the LEVEL-AT trial. Assessment of the QRS duration and ventricular activation time was performed during optimization of the AV interval. The optimization process was performed starting with a short AV interval with LBBP and looking for the fusion band with progressive prolongation of the AV interval in 10-ms increments. Results Median age was 62 years (Q1-Q3, 57–74 years), 40% were women, 20% had ischemic cardiomyopathy, and baseline LVEF was 29% (23%–36%). The baseline median QRS duration was 178 ms (168–187 ms), with a left ventricular activation time of 99 ms (90–109ms), a right ventricular activation time of 42 ms (34–71 ms), and a total ventricular activation time of 111 ms (105–131 ms). A non-tailored AV programming showed a QRS measured from intrinsic deflection of 142 ms (137–149 ms); when a tailored AV was programmed, the median QRS decreased to 124 ms (116–130 ms); measures from spike are shown in Table 1. Ventricular activation times showed shortening with a tailored approach (Table 1, Figure 1). Conclusion AV interval settings during LBBP may need to be individualized to optimize resynchronization, rather than relying on out-of-the-box programming.Tailoring the AV interval during LBBP.