Understanding important factors for arrhythmogenicity associated with transcatheter aortic valve implantation including left bundle branch block: Authors’ reply

We thank Kashkosh and colleagues1 for their interest in our study reporting the arrhythmic burden at 2-year follow-up in patients with new-onset left bundle branch block (LBBB) after transcatheter aortic valve replacement (TAVR) using an implantable cardiac monitor.2 The management of new-onset LBBB patients remains as an unmet need in the TAVR field. Following hospital discharge, new-onset LBBB has been associated with a two-fold increased risk of advanced conduction disturbances requiring permanent pacemaker implantation.3 Kashkosh and colleagues1 suggested a lack of negative clinical impact of new-onset LBBB following TAVR. However, a recent meta-analysis including close to 8000 patients showed an increased risk of death in new-onset LBBB patients, resolving the previous controversial data regarding the clinical outcomes in this context.2 On the other hand, the resolution of new-onset LBBB is observed in up to 20–30% of the patients at 1-year of follow-up, underscoring the complexity and variability [from HAVB (high-degree atrioventricular block) to electrocardiogram (ECG) normalization] in this group of patients.4 Kashkosh and colleagues1 also comment on two aspects regarding new-onset LBBB after TAVR: the depth of valve implantation and the type of transcatheter heart valve (THV) system. The depth of implantation is a well-known factor associated with new-onset LBBB after the procedure.5 However, its potential role on the regression of the LBBB or progression to HAVB during follow-up has not been demonstrated to date. A recent study including patients with new-onset LBBB after TAVR failed to identify any clinical or ECG variable (including implantation depth) associated with LBBB recovery over time.4 More data are needed focusing on the clinical, ECG, and procedural variables associated with LBBB recovery at follow-up in these patients. On the other hand, Kashkosh and colleagues stressed the potential benefits of the self-expandable Evolut/Evolut Pro THV system (e.g. less patient–prosthesis mismatch in small annulus) assuming an increased rate of new-onset LBBB. The use of the self-expandable Evolut/Evolut Pro system has been associated with a higher incidence of new-onset LBBB after the procedure.5 However, this aspect was out of the focus of our study, which evaluated exclusively the late arrhythmic events. Of note, no differences between valve types (self-expanding vs. balloon-expandable) were observed in late bradyarrhythmic events up to 2-year follow-up. In conclusion, more evidence including large prospective cohorts with uniform management is needed to better understand the factors for arrhythmogenicity in patients with new-onset LBBB after TAVR.6 Meanwhile, we agree with Kashkosh and colleagues that a closer follow-up including ambulatory ECG monitoring during the early period after discharge may be useful in such patients. Conflict of interest: Dr. Rodés-Cabau has received institutional research grants from Medtronic, Edwards Lifesciences, and Boston Scientific. The rest of authors have not reported any potential conflict of interest with respect to this paper.