Response to Letter Regarding Article, “Clinical Impact of Persistent Left Bundle-Branch Block After Transcatheter Aortic Valve Implantation With CoreValve Revalving System”
Authors: Francesco Bedogni, Azeem Latib, Federico De Marco, Mauro Agnifili, Jacopo Oreglia, Samuele Pizzocri, Roberto A. Latini, Stefania Lanotte, Anna Sonia Petronio, Marco De Carlo, Federica Ettori, Claudia Fiorina, Arnaldo Poli, Silvia Cirri, Stefano De Servi, Angelo Ramondo, Giuseppe Tarantini, Antonio Marzocchi, Rosario Fiorilli, Silvio Klugmann, Gian Paolo Ussia, Corrado Tamburino, Francesco Maisano, Nedy Brambilla, Antonio Colombo, Luca Testa
Journal: Circulation (2013)

We appreciate the interest of Prinzen et al about our article, 1 but some of their comments need to be addressed.Prinzen et al analyzed a mixed population of patients treated with CoreValve or Edwards Sapien prostheses. 2 Of note, their different influence on the cardiac conduction system is well known, 3 with the CoreValve being more prone to determine conduction disturbances as a consequence of the larger frame.Accordingly, we decided to specifically focus on the CoreValve, pooling >800 patients, which is more than double the population considered by Prinzen et al.It is clear that the internal and external validity (ie, the extent of systematic biases and the generalizability of the results) are highly affected by the sample size.Prinzen et al excluded patients who underwent pacemaker implantation within 30 days after transcatheter aortic valve replacement, which, in our opinion, makes little sense because the left bundle-branch block (LBBB) usually develops immediately and its short-term effect was unclear.The latter was one of the aims of our study.We excluded those who were implanted urgently within 48 hours, and, among the remaining patients, those showing a new-onset LBBB had a higher risk of pacemaker implantation within the first month after transcatheter aortic valve replacement.As for these points, Prinzen et al suggest that a considerable proportion of patients with LBBB was protected against bradyarrhithmic death.The logical consequence of this hypothesis is that the very tight follow-up we implemented for those patients was very successful and should be advocated on a routine basis.As for the diagnostic issue, the citation from Prinzen et al has little to do with the transcatheter aortic valve replacement scenario, and the criteria we used are accepted worldwide.With respect to the QRS duration in patients with LBBB, we found that the widening of the QRS was remarkable, reaching a mean duration of 142 ms (range of 130-155 ms).Prinzen et al probably interpreted 130 ms as the 25th percentile; it was instead the lower limit.Thus, their doubts seem groundless.Prinzen et al probably misinterpreted also the percentage of LBBB in our study: it was 43.2% (ie, close to the 51% they reported).This percentage decreased afterward, which is consistent with data from the literature.In conclusion, logistic EuroSCORE in our study was higher: this is a consequence of the fact that only patients at a very high or prohibitive risk for surgery were included.In such a population, which is supposed to be the real transcatheter aortic valve replacement population, it is conceivable that other predictive factors play a critical role in determining the prognosis.