Higher rates of pacemaker implantation after rapid-deployment intuity aortic valve replacement: can it be improved?

Recently, Herry et al. [1] reported a higher incidence of permanent pacemaker (PPM) implantation in patients undergoing surgical aortic valve replacement with a rapid-deployment bioprosthesis (RDB) as compared to standard aortic valves, even after propensity matching. Given that previous studies were mostly incomplete (e.g. on the incidence of baseline right bundle branch block) [2] and conclusions did not allow for a reliable analysis of risk factors, this study represents a first but significant step forward in the discussion of this issue. Despite the several study limitations (the ratio between the native aortic annular diameter and the size of the prosthesis was not available), the results are consistent with those of previous analyses in patients undergoing transcatheter aortic valve implantation (TAVI) and sutureless aortic valve replacement (Su-AVR). Similarities are therefore extremely interesting if we consider that—through risk factor analysis and procedural changes—TAVI and Su-AVR could reduce their rates of postoperative PPM implantation in the time [3, 4]. The structure of RDBs is very similar to TAVI and Su-AVR prostheses, all of which are designed for intra-annular positioning with a stent frame that has a radial force for fixation at the annulus. This implies a certain degree of oversizing for all the 3 valve models. The stent of TAVI valves and RDBs is longer and extends below the aortic annulus into the left ventricular outflow tract. The combination of annular calcification with valve oversizing represents a risk factor for the development of atrioventricular block after TAVI [5]. If surgical aortic valve replacement is performed using an RDB, calcifications are removed (at least those protruding or at risk of embolizing). Calcific deposits may however extend into the membranous portion of the interventricular septum, involving the left branching portion of the His-bundle. As reported by Herry et al., the choice of the prosthesis (RDB versus standard aortic valve) was left to the discretion of the surgeon: typically, surgeon prefers for an RDB in the majority of cases if massive calcifications were present. A fair comparison should measure preoperatively the calcium load between groups. Finally, if Su-AVR prostheses and RDBs are used, balloon dilation after stent deployment is performed at 4 atm (which is a pressure equal to 3040 mmHg, or 25 times higher than the normal systolic blood pressure, as recommended by the manufacturer) to enhance complete stent expansion. In a previous study from our group, balloon post-dilation at a lower pressure, along with the adoption of others technical improvements, was associated with a reduced rate of PPM implantation after Su-AVR [4]. Future studies may take advantage from the lessons learned from similar technologies so as to reduce the incidence of PPM implantation after surgical aortic valve replacement with an RDB.