Author + information
- Published online August 6, 2018.
- Michele Pighi, MD∗ ( and )
- Nicolo Piazza, MD, PhD
- Department of Medicine, Division of Cardiology, McGill University Health Centre, Montreal, Quebec, Canada
- ↵∗Address for correspondence:
Dr. Michele Pighi, Division of Cardiology, Department of Medicine, McGill University Health Centre, The Royal Victoria Hospital, 1001 Boulevard Décarie, Montréal, H4A 3J1 Quebec, Canada.
The occurrence of conduction disturbances and particularly new-onset left bundle branch block (LBBB) remains a frequent complication of transcatheter aortic valve replacement (TAVR) (1). New-onset LBBB occurs in 4% to 65% of patients undergoing TAVR; 18% to 65% with self-expandable CoreValve (Medtronic, Minneapolis, Minnesota) and 4% to 30% with SAPIEN/SAPIEN XT valves (Edwards Lifesciences, Irvine, California) (1). Compared with SAPIEN XT, the newer-generation SAPIEN 3 is associated with similar rates of new-onset LBBB (10.8% vs. 13.0%; p = ns) albeit suggestions of a higher rate of new permanent pacemaker (PPM) implantation (19.1% vs. 12.2%; p = 0.046) (2). To date, results from individual studies and meta-analyses investigating the association between new-onset LBBB and all-cause mortality have yielded inconsistent and conflicting results (3). The management of patients presenting with new-onset LBBB following TAVR remains controversial, mainly limited to post-procedural in-hospital monitoring and routine ambulatory examinations.
In this issue of JACC: Cardiovascular Interventions, Rodés-Cabau at al. (4) report the results of the MARE study (Ambulatory Electrocardiographic Monitoring for the Detection of High-Degree Atrio-Ventricular Block in Patients With New-Onset Persistent Left Bundle-Branch Block After Transcatheter Aortic Valve Implantation), a multicenter study implementing continuous cardiac monitoring for the detection of arrhythmic events in 103 consecutive patients presenting with new-onset persistent LBBB following TAVR with either a balloon-expandable SAPIEN XT/3 (n = 53) or self-expandable CoreValve/EvolutR (Medtronic, Minneapolis, Minnesota) (n = 50). Patients without new-onset LBBB were excluded from the study. The investigators used implantable cardiac monitors for assessing the global arrhythmic burden, the incidence of arrhythmias leading to a treatment change, and the incidence of high-degree atrioventricular block at 12-month follow-up.
The major findings of the MARE study can be summarized as follows: 1) a total of 1,553 arrhythmic events were detected in nearly one-half of patients (n = 44, 43%) with 1,443 episodes of tachyarrhythmia and 110 episodes of bradyarrhythmia; 2) arrhythmias were silent (asymptomatic) in 3 of 4 patients (34 of 44, 77%); and 3) a treatment change was instituted in nearly 1 of 5 patients (19 of 103, 18%) presenting with a new-onset LBBB or in nearly 1 of 2 patients (19 of 44, 43%) with new-onset LBBB identified with an arrhythmic event, and at 12 months a PPM or implantable cardioverter-defibrillator (ICD) was implanted in 11 of 103 patients (11%).
Previous studies have reported new-onset LBBB in roughly one-fourth of patients undergoing TAVR (1). Extrapolating from the given data, we calculated that new-onset LBBB occurred in approximately 8% (53 of 643) of balloon-expandable and 15% of self-expandable (50 of 333) valves. Although the Authors report an overall lower-than-ex-pected rate of persistent new-onset LBBB (10%) post TAVR, the definition of “persistence” required that LBBB remained for at least 3 days following TAVR. It is possible, therefore, that the lower than expected rate of new-onset LBBB is related to the exclusion of a proportion of patients with new-onset LBBB that resolved within 3 days post-procedure. Furthermore, the authors may have implemented risk mitigation protocols to avoid LBBB (e.g., depth of implantation, prosthesis oversizing) although this was not discussed in the paper (2,5).
The absence of a control group is an important limitation of the study, and would it not be interesting to explore and compare the arrhythmic burden in patients of similar age but not undergoing TAVR, or TAVR patients who did not develop new-onset LBBB? In a recent study, paroxysmal arrhythmias or transient conduction disorders were already detected in 23% of patients (102 of 435) with a 24-h Holter monitoring before undergoing TAVR (6). Implanting the loop recorder sometime before TAVR may have also provided additional information about new versus old arrhythmic events.
The MARE study showed numerically higher rates of new-onset LBBB in balloon-expanding than in self-expanding valves both at 30-day (68% vs. 59%) and 12-month (70% vs. 53%) follow-up, albeit statistically, it was not significant. This finding is divergent from previous reports suggesting that new-onset LBBB is more frequent following self-expanding (47.5% to 72.5%) than balloon-expanding (27.1% to 43.6%) valves (1).
In the current report, 20% and 22% of patients had complete resolution of LBBB at 30-day and 12-month follow-up, respectively. This suggests that most patients have LBBB recovery within the first 30 days following TAVR. Analysis of Figure 5 also suggests that resolution to a completely normal electrocardiogram occurred with greater frequency after self-expanding than balloon-expanding valves at both 30-day (24% vs. 16%) and 12-month (30% vs. 15%) follow-up, respectively. Although the MARE study was not powered for subgroup comparisons, these findings are intriguing and may generate new hypothesis testing.
The current study revealed a high burden of arrhythmic events within 30 days post-TAVR. Continuous ambulatory monitoring, however, showed that approximately 40% of all arrhythmic events occurred between 30 days and 12 months follow-up. These findings suggest that standard strategies are likely to fail in detecting a large proportion of arrhythmic episodes after discharge that could potentially progress toward more dangerous conditions such as high-degree atrioventricular block or severe bradycardia (detected in 1 of 5 patients in the present study). These data warrant further investigation into the potential role of continuous monitoring for the detection of conduction disturbances during the first year of follow-up.
The use of implantable continuous monitors provides new insights into the characteristics of arrhythmic events following TAVR. In particular, the authors observed that three-quarters of their patients with new-onset LBBB who developed arrhythmias were asymptomatic (i.e., silent). This finding has important implications in the context of atrial fibrillation, where the timely detection of the arrhythmia is of paramount importance in preventing possible cardioembolic complications. As reported in the MARE study, new atrial fibrillation/flutter episodes are not infrequent and were detected in 13% of patients (13 of 103 patients); approximately 50% of these cases required a change in therapeutic strategy.
The rates of PPM implantation (10%) in the MARE study are consistent with previous reports and meta-analyses (7). The median time to PPM in the current study, however, was 42 (6 to 217) days in contrast to a recent report from the Society of the Thoracic Surgeons (STS) showing that nearly 50% of patients receive their PPM within the first 3 days following the TAVR procedure (8). This discrepancy, possibly a consequence of an “aggressive” strategy of early PPM implantation, could be the result of increasing pressure on shorter hospital stays and cost reductions. Although appealing in the short term, an approach of “early pacemaker implantation” could lead to a significant proportion of patients experiencing transitory conduction disturbances and futile pacemaker insertions. Latest guidelines recommend a clinical observation period of up to 7 days before determining the transient or permanent nature of the conduction disturbance (Class I, Level of Evidence: C) (9).
The MARE study showed a rate of sudden cardiac death of 1% (1 of 103 patients), consistent with data from previous larger experiences (10). A recent meta-analysis comprising pooled data from 8 different studies (3) failed to show a significant relationship between new-onset LBBB and 1-year all-cause mortality, whereas a greater risk of 1-year cardiac mortality and sudden cardiac death was noted in patients with new-onset LBBB, particularly when the QRS duration was >160 ms. The current study identified ventricular tachycardia in 13% of patients (13 of 103), albeit only 1 had a sustained ventricular tachycardia. Although these represent intriguing findings, the small sample size limits the investigation into a possible association between sudden cardiac death and ventricular arrhythmias. These initial findings demand further research into the predictors of cardiovascular mortality/sudden death and the possible role of ICD in patients identified with sustained ventricular arrhythmias following TAVR.
In summary, the MARE study provides fascinating insights about conduction abnormalities and arrhythmias following TAVR. The nonrandomized nature of the study, the relatively small sample size, and the absence of a control group limit the extent of generalizations. The MARE study, however, has generated new dilemmas and questions while providing a strong stimulus and foundation for the development of new studies in this field. Ambulatory continuous cardiac monitoring could represent a powerful instrument in the hands of the clinician for a tailored therapy in patients at higher risk for conduction disturbances post-TAVR.
↵∗ Editorials published in JACC: Cardiovascular Interventions reflect the views of the authors and do not necessarily represent the views of JACC: Cardiovascular Interventions or the American College of Cardiology.
Dr. Piazza has been a consultant/proctor for HighLife, Medtronic, and MicroPort; and a consultant for Cephea. Dr. Pighi has reported that he has no relationships relevant to the contents of this paper to disclose.
- 2018 American College of Cardiology Foundation
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