IJCS | Volume 32, Nº5, September/October 2019

502 Cedenilla et al. Requirements for permanent pacemaker afterTAVI Int J Cardiovasc Sci. 2019;32(5):492-504 Original Article outflow tract. During implantation, the lower third of the prosthesis may compress the interventricular septum and the conduction system. 19,22,24,36 The Sapien ® prosthesis extends a few millimeters below the annular plane. The lower incidence of conduction disorders with the Sapien ® prosthesis is due to a higher implant and less extension of the prosthesis in the LV outflow tract. 19,22,24 The implantation of larger prostheses was associated with a greater need for pacemakers in this study. The mean prosthesis size of patients who had pacemaker implantedwas significantly higher than that of those who did not have any pacemaker implanted. The implantation of larger prostheses was also a predictor of the need for pacemakers after TAVI in a multicenter study that evaluated 243 patients in the UK. 36 The presence of previous conduction disorders is a risk factor for the development of AVB in both conventional surgery and TAVI. 19,20 In this study, patients with history of first-degree AVB had a 13-fold higher risk of pacemaker implantation compared to those without first-degree AVB. The presence of first-degree AVB before TAVI was also a predictor of the need for pacemakers in the FRANCE-TAVI Registry 16 and in the studies by De Carlo et al. and Bleiziffer et al. 37,38 In this study, patients with QRS complex duration ≥120 ms had a 5-fold increased risk of pacemaker implantation compared to those who did not have the same ECG finding before TAVI. The presence of previous conduction disorders was an independent predictor of the need for pacemakers in a meta-analysis published by Siontis et al. 19 In the multivariate analysis, the only variable considered to be an independent predictor of the need for pacemaker implantation after TAVI was the presence of first-degree AVB before implantation of the prosthesis. It should be noted that this is a retrospective design study that reports the initial experience of a single center with a small sample size. Thus, the multivariate analysis presented has low statistical power, which means that there is a considerable chance of type II error. Despite these limitations, the results found were similar to those described in the literature. Other factors associated with the development of conduction disorders after TAVI, such as depth of self- expanding prostheses and calcification in the outflow tract were not evaluated in this study. The excessively low valve implantation was associated with the development of conduction disorders after TAVI in some series published in the literature. 19,22,24 Piazza described a significant correlation between the depth of the implant in the LVOT and the onset of LBBB after implantation of self-expanding prosthesis. 22 History of conduction disorders after TAVI is not well understood yet, because it is a relatively new technology and further studies are required to say the best course of action to be taken in the development of conduction disorders. Implantation of permanent pacemaker after TAVI is justified among seniors with cardiac structural disease. Potential problems related to the use of provisional transvenous pacemaker, such as ventricular perforation, infection, prolonged immobilization and longer hospital stay, contribute to reduced threshold of indication of permanent artificial cardiac pacing. It is known that displacement of the electrode of the provisional pacemaker can cause catastrophic failures with potentially serious consequences, exposing the patient to the risk of asystole and death. These facts justify the decision of implanting permanent pacemaker earlier, a conduct supported by experts, but not based on the results of randomized studies, as these are not available in this particular situation. 39 On the other hand, implantation of permanent pacemaker is also not risk-free. Elderly patients with multiple comorbidities have an increased risk of hematoma, pocket infection and endocarditis. Besides, cardiac pacingmay lead to interventricular dyssynchrony and worsening of long-term ventricular function. 40 In a sub-analysis of the PARTNER study, the presence of pacemaker was an independent predictor of mortality in one year. 21 In this study, 8 of the 9 patients who died during follow-up had either LBBB or permanent pacemaker. Houthuizen et al. demonstrated an association between new LBBB after TAVI and increased mortality. 25 The 60% increase in 1-year mortality in patients who developed new LBBB after TAVI in the study by Houthuizen et al. suggests that the onset of LBBB after TAVI is a serious complication, which attenuates the benefit achieved by the procedure. It should be noted that in this study the prostheses used were first-generation prostheses. Despite the technological development of the new prostheses and the experience gained with the procedure, the incidence of conduction disorders after TAVI is still a source of concern and has inconsistent results depending on the prosthesis used. The need for a permanent pacemaker