We have read with interest the article concerning atrioventricular conduction disturbances secondary to implantation of the CoreValve transcatheter aortic valve (Medtronic CoreValve System [MCS]) published by López-Aguilera et al1 in Revista Española de Cardiología. After congratulating the authors for adding to the evidence regarding this feared complication, we believe that some of our reflections on the timeline of these disturbances would be highly pertinent.
The implantation of MCS prostheses has been related to the need for pacemaker implantation in up to 35% of patients.2 This high rate is due to the development of a complete atrioventricular block (CAVB) during or after valve implantation. The early timing of pacemaker implantation, sometimes within the same procedure, could be due to the lack of data on the time course of CAVB secondary to valve implantation, which may have influenced the reported rates. However, there is a growing body of evidence of the temporality of these disturbances. A number of authors have reported that around 50% of the patients treated with the MCS prosthesis eventually returned to their normal rhythm,3,4 suggesting that perhaps the causal mechanism of the CAVB is only temporal. This was pointed out by López-Aguilera et al1 upon observing the improvement in the electrophysiological parameters just days after the procedure.
On the other hand, there is a group of patients treated with the MCS prosthesis who require a pacemaker during long-term follow-up. Although several authors consider CAVB to be related to valve implantation if it occurs within 30 days,5,6 it is difficult to set an exact time limit on the causality of valve implantation in the development of CAVB. Importantly, the percentage of patients treated with the MCS prosthesis who require a pacemaker during the first year of follow-up is higher than that expected for a population of similar age and characteristics.7,8 In this respect, López-Aguilera et al1 found that 3.8% of the patients treated with MCS prostheses required a pacemaker sometime after the second month of follow-up due to the development of CAVB, and that 1.1% needed it because of symptoms associated with significant alterations in a late electrophysiological study. Thus, there appears to be a causal relationship between valve implantation and the development of CAVB during long-term follow-up. This theory may be supported by the fact that some authors have demonstrated the protective role of pacemaker implantation against sudden death in patients treated with transcatheter aortic valve prostheses.9
To correctly select those patients who require a permanent pacemaker after valve implantation, is it essential to establish a time limit prior to undertaking pacemaker implantation, since the CAVB may be reversible. It is also necessary to define the predictive factors related to the development of a late CAVB. Thus, patients who present with factors that are clearly recognized in the medical literature to be predictive of CAVB after transcatheter aortic valve implantation, such as right bundle branch block and the depth of valve implantation, will require close follow-up.
CONFLICTS OF INTERESTC. Morís is a proctor for the CoreValve system and a member of Medtronic's Latin American Advisory Board.