Author + information
- Lutz Buellesfeld, MD,
- Dik Heg, PhD and
- Stephan Windecker, MD⁎ ()
- ↵⁎Department of Cardiology, Swiss Cardiovascular Center Bern, Bern University Hospital, 3010 Bern, Switzerland
We thank Dr. Houthuizen and colleagues for their interest in our study (1), which reported that periprocedural permanent pacemaker implantation among patients undergoing transcatheter aortic valve implantation (TAVI) does not affect mortality during follow-up through 1 year. Houthuizen and colleagues are concerned by the lack of a sample size calculation and question the validity of our findings in view of previous pacemaker studies, namely, the MOST (Mode Selection Trial) and the DAVID (Dual Chamber and VVI Implantable Defibrillator) trial (2,3), as well as their own study suggesting a negative prognostic impact of new onset left bundle branch block after TAVI (4).
Our study is the first report to address the impact of permanent pacemaker implantation on mortality among patients undergoing TAVI, and we acknowledge that our findings are exploratory and not conclusive as it was limited to 2 institutions and high-risk patients. The number of patients and accumulated events were small, and 95% confidence intervals of hazard ratios wide. The present study should, therefore, be the impetus to address this issue in prospectively planned larger cohort studies.
The MOST and the DAVID trials have shown a negative impact of right ventricular pacing by increasing heart failure hospitalization but not mortality. Of note, these findings cannot be extrapolated to the issue of permanent pacemaker implantation in the context of TAVI. Both the MOST study and the DAVID trial included only patients with sinus node dysfunction, in whom dual chamber or right atrial pacing would have been technically suitable, alternative pacing modes. Conversely, TAVI-related permanent pacemaker implantation is the result of transient or permanent impairment of atrioventricular (AV) conduction, which was an exclusion criterion for participation in MOST and DAVID. Moreover, patients undergoing TAVI substantially differ from patients included in the MOST and DAVID studies in terms of a higher cardiac risk profile and comorbidities, rendering any extrapolation between these studies inappropriate.
As highlighted in the title of our manuscript, we analyzed the effect of pacemaker implantation rather than conduction disturbances on all-cause mortality. In view of rates of 1-year mortality in the range of 24% to 31% after TAVI, it remains of interest whether permanent pacemaker implantation as one of the most frequent TAVI adverse events has a prognostic impact on this patient population.
As with any pacemaker population, the group of patients with a permanent pacemaker after TAVI is highly heterogeneous by nature and consists of patients with various pacemaker indications (high-degree AV block, new-onset left bundle branch block with first-degree AV block, slow atrial fibrillation), variable rates of ventricular stimulation during follow-up, spontaneous recovery of AV conduction no longer requiring a pacemaker, as well as patients with recovery followed by relapse of severe conduction abnormality. Therefore, the results of our study do not provide insights on the clinical relevance of a specific conduction abnormality, but describe the clinical prognosis of the event “TAVI-related pacemaker implantation” under current practice standards. These standards include post-procedural rhythm monitoring for 48 h to allow for AV conduction recovery and avoidance of permanent pacemaker implantation in some patients, but also includes early pacemaker implants in case of severe conduction disturbances, as it effectively precludes deleterious effects related to temporary pacemaker dislocation and bradycardia induced ventricular fibrillation. In fact, a growing body of evidence indicates that TAVI-induced conduction disturbances do not tend to recover over time, supporting an early, aggressive strategy of permanent pacemaker implantation (5).
The negative prognostic impact of left bundle branch block among patients with cardiovascular disease, including ischemic heart disease and dilated cardiomyopathy, has been previously shown, and we read with interest the results of the study by Houthuizen et al. among patients undergoing TAVI. Comparing this study with ours, the results do not contradict but rather complement each other as both studies address the issue of TAVI-induced AV conduction abnormalities but from a different angle. In this context, it is important to realize that patients receiving a permanent pacemaker were specifically excluded from the study by Houthuizen et al. (4), resulting in a different patient population.
Pacemaker implantation is life-saving among patients with high-degree AV conduction abnormalities, and it remains to be seen whether some patients with TAVI-induced left bundle branch block included in the study by Houthuizen et al. (4) would have derived a benefit when implanted with a pacemaker. Given the reports of both recovery as well as late onset of severe conduction disturbances after TAVI, it remains a difficult clinical judgment who should undergo permanent pacemaker implantation. Future efforts with focus both on how to avoid conduction abnormalities and to define TAVI-specific criteria and on how to treat them appropriately once they occur will importantly impact the further evolution of TAVI.
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