Leadless pacing using the transcatheter pacing system (Micra TPS) in the real world: initial Swiss experience from the Romandie region

We have read with great interest the manuscript by Valiton et al.1 entitled ‘Leadless pacing using the transcatheter pacing system (Micra TPS) in the real world: initial Swiss experience from the Romandie region’. In this retrospective analysis including 92 patients, the authors reported a significantly higher rate of major complications (9.8%) during the first year when compared with the Micra Transcatheter Pacing System Post-Approval Registry (2.7%) and our own monocentric real-world experience (1.5%).2,3 This difference is surprizing and raises several comments and questions. Manufacturer recommendations seem not to have been followed for four patients with high pacing threshold at implantation. In these cases, the operators seem to have launched the device before reaching a pacing threshold <1 V, without trying alternative positions than the apex or up to the recommended 10 redeployments. Of course, the physician could accept a suboptimal threshold until 2.00 V after confirmation of the stability of the device (engagement of at least two tines confirmed by ‘pull and hold’ test) if the risk of complication related to reposition is considered very high. In a recent paper, Piccini et al. confirmed that initial elevated pacing threshold is predictive for a high threshold during follow-up.4 Therefore, those four patients may have largely contributed to the number of patients with elevated pacing threshold reported during follow-up, that was not observed in the Micra Transcatheter Pacing System Post-Approval Registry and our study. The fact that strict compliance of implantation protocol might contribute to reduce complications is also illustrated in Cases 4 and 5. In Case 4 who developed an intracardiac thrombus, it is not described whether or not an effective dose of intravenous heparin was administered during the procedure. For Case 5 (recurrent monomorphic ventricular tachycardia during the implant procedure within a patient with coronary disease and probably hypertrophic cardiomyopathy), one might wonder if it would have been wiser to switch to a conventional pacing system during an initial experience with leadless pacing devices. Then this major complication would have been viewed as an unsuccessful rather than complicated procedure. Finally, we think that the number of major complications might have been overestimated by the definition the authors used. For instance, Case 6 was considered as having major complication due to a prolonged hospital stay without a clear causal relationship between the reason for the prolonged hospital stay and the implantation procedure. Despite these remarks we do agree with Valiton et al. that training and experience plays an important role for limiting major complications. We think that their experience rather is illustrative of a poor implementation strategy (too many centres without the necessary expertise), than of a poor technology. This is indirectly confirmed by the lower rate of complications we observed in 67 patients (with 30% of challenging cases for conventional pacing) implanted by a single operator (C.G.), as compared with the seven different cardiologists in Valiton’s paper.3 Conflict of interest: C.G., R.W. received research funding from Biotronik, Boston Scientific and Medtronic, speakers and consultancy fees from Biotronik, Boston Scientific, Medtronic and Abbot.