https://orcid.org/0000-0002-7197-8415
Abstract
Catheter ablation of frequent idiopathic pre-mature ventricular contractions (PVC) is increasingly performed. While potential benefits of contact force (CF)-sensing technology for atrial fibrillation ablation have been assessed in several studies, the impact of CF-sensing on ventricular arrhythmia ablation remains unknown. This study aimed to compare outcomes of idiopathic outflow tract PVC ablation when using standard ablation catheters as opposed to CF-sensing catheters.
In a retrospective multi-centre study, unselected patients undergoing catheter ablation of idiopathic outflow tract PVCs between 2013 and 2016 were enrolled. All procedures were performed using irrigated-tip ablation catheters and a 3D electro-anatomical mapping system. Sustained ablation success was defined as a ≥80% reduction of pre-procedural PVC burden determined by 24 h Holter ECG during follow-up. Overall, 218 patients were enrolled (median age 52 years, 51% males). Baseline and procedural data were similar in the standard ablation (24%) and the CF-sensing group (76%). Overall, the median PVC burden decreased from 21% (IQR 10–30%) before ablation to 0.2% (IQR 0–3.0%) after a median follow-up of 2.3 months (IQR 1.4–3.9 months). The rates of both acute (91% vs. 91%, P = 0.94) and sustained success (79% vs. 74%, P = 0.44) were similar in the standard ablation and the CF-sensing groups. No differences were observed in subgroups according to arrhythmia origin from the RVOT (65%) or LVOT (35%). Complications were rare (1.8%) and evenly distributed between the two groups.
The use of CF-sensing technology is not associated with increased success rate nor decreased complication rate in idiopathic outflow tract PVC ablation.
This study assessed the potential benefits of contact force (CF)-sensing technology compared with standard ablation catheters for ablation of idiopathic pre-mature ventricular contractions (PVCs).
Catheter ablation was very safe with a complication rate of 1.8%, and showed acute success in 91% and sustained success in 75% of cases in the overall cohort.
No significant differences were observed in the acute success or sustained success rates between the CF-sensing and standard ablation groups, also when analysed for subgroups of RVOT and LVOT sites separately.
The use of CF-sensing catheters as opposed to standard ablation catheters was not associated with increased success rate nor with decreased complication rate in idiopathic outflow tract PVC ablation.
Introduction
Radiofrequency catheter ablation has emerged as the preferred treatment option for patients with symptomatic and/or frequent idiopathic pre-mature ventricular contractions (PVCs) over the last two decades.1,2 It is a safe and effective method, yet with up to 30% recurrence rates even in very experienced hands.1 Proposed failure mechanisms include inaccurate mapping, at times due to infrequent PVCs during the ablation procedure3; the presence of multiple PVC morphologies1; deep intra-mural (such as in the septum)3 or intra-cavitary locations of PVC foci (such as with papillary muscles),1 or origin from areas difficult to access (such as the LV summit)4; shift in the anatomic map during sinus rhythm and PVC; or insufficient contact between the catheter tip and the tissue during ablation resulting in formation of oedema rather than necrosis.5
In order to address the issue of catheter contact, catheters capable of measuring, and displaying catheter-tissue contact force (CF) were developed.6 The use of direct CF information rather than indirect measures of contact (such as tactile feedback, signal characteristics, or impedance fall during ablation) theoretically has the potential to improve both ablation efficacy and safety by more accurate radiofrequency lesion titration and also by minimizing the risk of mechanical injury due to excessive CF. Since their introduction in the early 2010s, CF-sensing catheters have seen a dramatic global uptake and have largely replaced standard ablation catheters for complex ablations.5 After initial observational studies had shown improved outcomes for atrial fibrillation (AF) ablation with the use of CF-sensing catheters over standard ablation catheters,7 randomized-controlled trials have failed to show superiority in terms of AF recurrence.8 In parallel to AF ablation, the use of CF-sensing catheters has dramatically increased for ventricular arrhythmia ablations as well, but data on the impact of CF-sensing technology on procedural efficacy and safety of ablation of ventricular arrhythmias remain sparse.
The objective of this multi-centre study was to assess the impact of the use of CF-sensing ablation catheters as opposed to standard ablation catheters on the outcomes of ablation of idiopathic PVCs originating from the outflow tracts.
Methods
Study design, setting, and selection of participants
This retrospective multi-centre study was conducted in nine ablation centres in Switzerland (Swiss-PVC). Unselected patients undergoing irrigated-tip radiofrequency catheter ablation of idiopathic PVCs originating from the outflow tracts using a 3D electroanatomical mapping system between 2013 and 2016 were enrolled. Patients with structural heart disease, ventricular tachycardia rather than PVCs and those with missing baseline or follow-up Holter monitoring data were excluded.
The study was carried out in accordance with the principles of the Declaration of Helsinki and was approved by all local Ethics Committees. The authors had full access to and take full responsibility for the integrity of the data. The restrictions set by the local Ethics Committees do not permit sharing the full dataset of variables underlying the findings of this study.
Baseline evaluation
Prior to the procedure, patients underwent clinical evaluation; a detailed medical history including drug therapies and standard blood tests was obtained. A pre-procedural Holter monitoring of at least 24 h duration was performed to evaluate the PVC burden prior to ablation. Transthoracic echocardiography was performed in all patients to exclude structural heart disease and to assess the left ventricular ejection fraction (LVEF). LVEF was quantified using the Simpson formula. Cardiac magnetic resonance imaging was additionally performed at the operator’s discretion as clinically indicated in cases with ambiguous echocardiographic findings.
Ablation procedure
Prior to the ablation, all anti-arrhythmic medications (except amiodarone) were withdrawn for five half-lives. All ablation procedures were guided by a 3D electro-anatomical mapping system (CARTO 3, Biosense-Webster, Diamond Bar, CA, USA). A standard 3.5 mm irrigated-tip catheter (Biosense Webster Navistar Thermocool or Thermocool SF) or a 3.5 mm irrigated-tip CF-sensing catheter (Biosense Webster Thermocool SmartTouch) was used for mapping and ablation. Ablation settings and CF targets were left at the operator’s discretion. Intra-venous sedation was minimized to avoid anaesthesia-related PVC suppression. Isoproterenol infusion was used at the operator’s discretion in order to induce PVCs in cases where spontaneous PVCs were otherwise too infrequent for activation mapping. Acute ablation success was defined as successful elimination of the targeted PVC without signs of recovery during a 30 min waiting period at the end of the procedure.
Follow-up
Any antiarrhythmic medication used previously was discontinued in cases where the ablation was acutely successful. Sustained ablation success was defined as a >80% reduction of pre-ablation PVC burden determined based on a 24 h Holter ECG at 1–3 months follow-up.9
Statistical analysis
Categorical variables are expressed as numbers (percentages) and continuous variables as medians [inter-quartile range (IQR)]. Comparisons between groups were made using χ2 method for categorical and Mann–Whitney U test for continuous variables. To evaluate predictors of sustained ablation success, binary logistic regression analysis was performed. Results are reported as hazard ratios (HR) with 95% confidence intervals (CIs).
Statistical analyses were performed using IBM SPSS Statistics for Windows, Version 25.0. IBM, Armonk, NY, USA. All tests were performed at a two-sided 5% significance level with two-sided 95% CIs.
Results
Patient characteristics
Overall, 218 patients with frequent and/or symptomatic PVC were enrolled. The baseline patient characteristics are summarized in Table 1. Median age was 52 years (IQR 40–63) and 51% of the patients were male. Prior to ablation, median LVEF was 60% (IQR 50–65) and 23% of patients had an LVEF <50%. The median pre-procedural PVC burden was 21% (IQR 10–30%). In total, 77% patients were previously treated with an anti-arrhythmic medication: beta-blocker (61%), calcium-channel-blocker (20%), class Ic drug (6%), or amiodarone (2%); these patients were either refractory to pharmacotherapy or did not tolerate the treatment.
Baseline characteristics of patients according to catheter type used
| All patients (n = 218) | Standard ablation catheter (n = 53) | CF-sensing ablation catheter (n = 165) | P-value | |
|---|---|---|---|---|
| Baseline characteristics | ||||
| Age, years | 52 (40–63) | 52 (41–66) | 52 (39–63) | 0.81 |
| Male sex (%) | 110 (51) | 26 (49) | 84 (51) | 0.81 |
| PVC burden pre-ablation (%) | 21 (10–30) | 23 (13–30) | 21 (10–30) | 0.45 |
| LVEF pre-ablation (%) | 60 (50–65) | 60 (50–65) | 60 (50–65) | 0.84 |
| Beta-blocker (%) | 132 (61) | 27 (51) | 105 (64) | 0.10 |
| Ca-channel blocker (%) | 44 (20) | 10 (19) | 34 (21) | 0.78 |
| Class Ic drug (%) | 14 (6) | 4 (8) | 10 (6) | 0.70 |
| Amiodarone (%) | 5 (2) | 0 (0) | 5 (3) | 0.20 |
| All patients (n = 218) | Standard ablation catheter (n = 53) | CF-sensing ablation catheter (n = 165) | P-value | |
|---|---|---|---|---|
| Baseline characteristics | ||||
| Age, years | 52 (40–63) | 52 (41–66) | 52 (39–63) | 0.81 |
| Male sex (%) | 110 (51) | 26 (49) | 84 (51) | 0.81 |
| PVC burden pre-ablation (%) | 21 (10–30) | 23 (13–30) | 21 (10–30) | 0.45 |
| LVEF pre-ablation (%) | 60 (50–65) | 60 (50–65) | 60 (50–65) | 0.84 |
| Beta-blocker (%) | 132 (61) | 27 (51) | 105 (64) | 0.10 |
| Ca-channel blocker (%) | 44 (20) | 10 (19) | 34 (21) | 0.78 |
| Class Ic drug (%) | 14 (6) | 4 (8) | 10 (6) | 0.70 |
| Amiodarone (%) | 5 (2) | 0 (0) | 5 (3) | 0.20 |
Data are presented as n (%) or median (IQR).
CF, contact-force; LVEF, left ventricular ejection fraction; PVC, pre-mature ventricular contraction.
Baseline characteristics of patients according to catheter type used
| All patients (n = 218) | Standard ablation catheter (n = 53) | CF-sensing ablation catheter (n = 165) | P-value | |
|---|---|---|---|---|
| Baseline characteristics | ||||
| Age, years | 52 (40–63) | 52 (41–66) | 52 (39–63) | 0.81 |
| Male sex (%) | 110 (51) | 26 (49) | 84 (51) | 0.81 |
| PVC burden pre-ablation (%) | 21 (10–30) | 23 (13–30) | 21 (10–30) | 0.45 |
| LVEF pre-ablation (%) | 60 (50–65) | 60 (50–65) | 60 (50–65) | 0.84 |
| Beta-blocker (%) | 132 (61) | 27 (51) | 105 (64) | 0.10 |
| Ca-channel blocker (%) | 44 (20) | 10 (19) | 34 (21) | 0.78 |
| Class Ic drug (%) | 14 (6) | 4 (8) | 10 (6) | 0.70 |
| Amiodarone (%) | 5 (2) | 0 (0) | 5 (3) | 0.20 |
| All patients (n = 218) | Standard ablation catheter (n = 53) | CF-sensing ablation catheter (n = 165) | P-value | |
|---|---|---|---|---|
| Baseline characteristics | ||||
| Age, years | 52 (40–63) | 52 (41–66) | 52 (39–63) | 0.81 |
| Male sex (%) | 110 (51) | 26 (49) | 84 (51) | 0.81 |
| PVC burden pre-ablation (%) | 21 (10–30) | 23 (13–30) | 21 (10–30) | 0.45 |
| LVEF pre-ablation (%) | 60 (50–65) | 60 (50–65) | 60 (50–65) | 0.84 |
| Beta-blocker (%) | 132 (61) | 27 (51) | 105 (64) | 0.10 |
| Ca-channel blocker (%) | 44 (20) | 10 (19) | 34 (21) | 0.78 |
| Class Ic drug (%) | 14 (6) | 4 (8) | 10 (6) | 0.70 |
| Amiodarone (%) | 5 (2) | 0 (0) | 5 (3) | 0.20 |
Data are presented as n (%) or median (IQR).
CF, contact-force; LVEF, left ventricular ejection fraction; PVC, pre-mature ventricular contraction.
Ablation procedures and follow-up
The procedural characteristics are summarized in Table 2. The origin of the PVC’s was mapped to the RVOT in 141 patients (65%) and in the LVOT in 77 patients (35%). Median procedure time was 127 min (IQR 91–174) and median ablation time was 341 s (IQR 136–555). Acute ablation success was achieved in 91% of the patients. Complications occurred in 1.8% of patients (see below for details).
Procedural characteristics of patients according to catheter type used
| All patients (n = 218) | Standard ablation catheter (n = 53) | CF-sensing ablation catheter (n = 165) | P-value | |
|---|---|---|---|---|
| Procedure duration (min) | 127 (91–174) | 120 (93–160) | 130 (90–180) | 0.23 |
| Ablation time (s) | 341 (136–555) | 341 (145–524) | 341 (120–591) | 0.85 |
| Ablation power (W) | 27 (25–30) | 30 (26–31) | 26 (25–30) | 0.09 |
| Fluoroscopy time (min) | 6 (3–14) | 6 (3–14) | 5 (2–13) | 0.91 |
| Multiple morphologies targeted (%) | 27 (12) | 5 (9) | 22 (13) | 0.45 |
| Acute success (%) | 198 (91) | 48 (91) | 150 (91) | 0.94 |
| Ablation site | ||||
| RVOT (%) | 141 (65%) | 30 (57%) | 111 (67%) | 0.38 |
| LVOT (%) | 77 (35%) | 23 (43%) | 54 (33%) | 0.38 |
| All patients (n = 218) | Standard ablation catheter (n = 53) | CF-sensing ablation catheter (n = 165) | P-value | |
|---|---|---|---|---|
| Procedure duration (min) | 127 (91–174) | 120 (93–160) | 130 (90–180) | 0.23 |
| Ablation time (s) | 341 (136–555) | 341 (145–524) | 341 (120–591) | 0.85 |
| Ablation power (W) | 27 (25–30) | 30 (26–31) | 26 (25–30) | 0.09 |
| Fluoroscopy time (min) | 6 (3–14) | 6 (3–14) | 5 (2–13) | 0.91 |
| Multiple morphologies targeted (%) | 27 (12) | 5 (9) | 22 (13) | 0.45 |
| Acute success (%) | 198 (91) | 48 (91) | 150 (91) | 0.94 |
| Ablation site | ||||
| RVOT (%) | 141 (65%) | 30 (57%) | 111 (67%) | 0.38 |
| LVOT (%) | 77 (35%) | 23 (43%) | 54 (33%) | 0.38 |
Data are presented as n (%) or median (IQR).
LVOT, left ventricular outflow tract; RVOT, right ventricular outflow tract.
Procedural characteristics of patients according to catheter type used
| All patients (n = 218) | Standard ablation catheter (n = 53) | CF-sensing ablation catheter (n = 165) | P-value | |
|---|---|---|---|---|
| Procedure duration (min) | 127 (91–174) | 120 (93–160) | 130 (90–180) | 0.23 |
| Ablation time (s) | 341 (136–555) | 341 (145–524) | 341 (120–591) | 0.85 |
| Ablation power (W) | 27 (25–30) | 30 (26–31) | 26 (25–30) | 0.09 |
| Fluoroscopy time (min) | 6 (3–14) | 6 (3–14) | 5 (2–13) | 0.91 |
| Multiple morphologies targeted (%) | 27 (12) | 5 (9) | 22 (13) | 0.45 |
| Acute success (%) | 198 (91) | 48 (91) | 150 (91) | 0.94 |
| Ablation site | ||||
| RVOT (%) | 141 (65%) | 30 (57%) | 111 (67%) | 0.38 |
| LVOT (%) | 77 (35%) | 23 (43%) | 54 (33%) | 0.38 |
| All patients (n = 218) | Standard ablation catheter (n = 53) | CF-sensing ablation catheter (n = 165) | P-value | |
|---|---|---|---|---|
| Procedure duration (min) | 127 (91–174) | 120 (93–160) | 130 (90–180) | 0.23 |
| Ablation time (s) | 341 (136–555) | 341 (145–524) | 341 (120–591) | 0.85 |
| Ablation power (W) | 27 (25–30) | 30 (26–31) | 26 (25–30) | 0.09 |
| Fluoroscopy time (min) | 6 (3–14) | 6 (3–14) | 5 (2–13) | 0.91 |
| Multiple morphologies targeted (%) | 27 (12) | 5 (9) | 22 (13) | 0.45 |
| Acute success (%) | 198 (91) | 48 (91) | 150 (91) | 0.94 |
| Ablation site | ||||
| RVOT (%) | 141 (65%) | 30 (57%) | 111 (67%) | 0.38 |
| LVOT (%) | 77 (35%) | 23 (43%) | 54 (33%) | 0.38 |
Data are presented as n (%) or median (IQR).
LVOT, left ventricular outflow tract; RVOT, right ventricular outflow tract.
After a median follow-up of 2.3 months (IQR 1.4–3.9), the median PVC burden decreased from 21% (IQR 10–30%) before ablation to 0.2% (IQR 0–3.0%, P < 0.001 for comparison). The rate of sustained ablation success rate was 75% in the overall cohort. No differences in ablation success were observed between those with an ablation target in the RVOT and those in the LVOT (79% vs. 69%, P = 0.11).
Impact of ablation catheter technology on outcomes
Mapping and ablation were performed using a standard ablation catheter in 53 patients (24%) and a CF-sensing catheter in 165 patients (76%). Given the observational non-randomized study design, the use of the ablation catheter type changed over time (Figure 1).
Change in the use of ablation catheter technology over time.
No differences in baseline or procedural characteristics were observed between the two groups (Tables 1 and 2). Acute success rates were similar in both groups (91% vs. 91%, P = 0.94, Figure 2). During follow-up, the rates of sustained success were similar in both groups (79% vs. 74%, P = 0.44; Figure 2).
Ablation success according to catheter type used.
No differences in ablation success were observed regarding the ablation catheter used in subgroups according to arrhythmia origin in the RVOT vs. LVOT. Acute and sustained ablation success were 87% vs. 91% (P = 0.48) and 80% vs. 78% (P = 0.85) in the RVOT and 96% vs. 91% (P = 0.46) and 78% vs. 65% (P = 0.24) in the LVOT (Figure 3). By multi-variable analysis, none of the variables was able to independently predict sustained ablation success (Figure 4).
Ablation success according to catheter type used in subgroups of RVOT (A) and LVOT (B) sites. LVOT, left ventricular outflow tract; RVOT, right ventricular outflow tract.
Multivariable analysis for predictors of sustained procedural success.
Procedural complications were rare and occurred in four patients (1.8%) with a similar distribution between the two catheter groups (P = 0.23). In the standard ablation catheter group, two patients developed pericarditis requiring pharmacological management. In the CF-sensing catheter group, one patient developed a cardiac tamponade requiring pericardiocentesis and one had a splenic artery embolism that was managed conservatively.
Comparison between ablation centres
In a sensitivity analysis, the results were compared between the nine centres. Sustained success rates ranged from 64% to 82%. When comparing sustained success rates according to the type of ablation catheter used (standard ablation catheter group vs. CF-sensing catheter group), the ranges were 67–88% and 57–85%. We did not find a significant difference between the two catheter types in none of the participating centres (P-values for comparison ranging from 0.19 to 0.80).
Discussion
In view of the rapid uptake and wide-spread use of CF-sensing catheters in complex cardiac ablation procedures, this is the first multi-centre study assessing potential advantages of CF-sensing catheters over standard ablation catheters for ablation of idiopathic outflow tract PVCs. Our main findings are as follows.
First, procedural characteristics including procedure time, ablation time, and fluoroscopy time did not differ between the standard ablation group and the CF-sensing group. Secondly, acute success was achieved in 91% of patients in both groups. Thirdly, procedural complications were rare (1.8%) and evenly distributed between the two groups, indicating a high procedural safety. And finally, sustained ablation success assessed by 24 h Holter recording after a median follow-up of 2.3 months was observed in 79% of the patients in the standard ablation group and 74% of the patients in the CF-sensing group.
The theoretical rationale for the use of CF-sensing catheters in idiopathic PVC ablation is straightforward: CF-sensing catheters provide continuous, real-time information about the catheter-tissue CF, which is a key determinant of lesion size.10 Excessive CF increases the risk of complications, including perforation, steam pop, and thrombus formation,11 while low CF does not result in adequate lesions.12 Accordingly, one would expect that the ability to optimize lesion titration based on direct CF information would improve ablation outcomes in idiopathic PVC ablation.
In our real-world experience, the CF-sensing catheters at this point in time, however, were not able to meet these expectations in idiopathic PVC ablation. Several factors might have contributed to the lack of superiority of CF-sensing catheters in our study: first, accurate mapping of the PVC focus is more important for ablation success than mere catheter contact during the focal ablation. This is an important difference in procedural workflow when compared, for example, with pulmonary vein isolation or linear ablation where lesion depth and contiguity are key factors. Secondly, CF-sensing catheters are slightly stiffer with a longer non-deflectable tip due to the additional technology in the shaft and tip, which at times might be a disadvantage for catheter manipulation in small outflow tracts. Thirdly, the anatomy of the outflow tracts can represent a challenge and intra-mural foci might be hard to reach even with CF technology. This concept is supported by the fact that outflow-tract arrhythmias sometimes require ablation from both the RVOT and LVOT or from the endocardial and epicardial side (mostly coronary sinus) to create adequate lesions.13,14 Fourthly, while the technical advantage of CF-sensing technology is important, a holistic concept of lesion optimization should also include metrics beyond CF, such as catheter orientation with tissue and force directionality,15 RF power and duration, impedance fall, lesion continuity and contiguity, homogeneity of force, and tissue thickness.5 And lastly, the creation of permanent trans-mural lesions remains a challenge. Despite CF and the aforementioned factors, temporary suppression of PVC foci due to transient tissue injury or oedema as a reason for subsequent recurrence of arrhythmia can still neither be completely excluded nor reliably detected despite the use of CF-sensing catheters.16
Our findings have to be interpreted also in view of the existing literature on idiopathic PVC ablation. Overall, the results observed in our study fit well into the range of reported sustained PVC ablation success rates, varying from 70% to 90% as well as of the low complication rates.1,17,18 With regards to the use of CF-sensing catheter technology for PVC ablation, a prior study by Zhao et al.19 reported shortening of the procedure, but no differences in terms of success or complications. Another study by Hendriks et al.20 did not find a difference in terms of complications and acute or sustained success between CF-sensing and standard ablation catheters when looking at idiopathic and structural ventricular arrhythmia cases. Accordingly in line with these observations in single-centre pilot studies, our multi-centre study also indicates that CF-sensing catheters do not fulfil the early premise of enhancing ablation efficacy or safety at this point in time.
Limitations
Potential limitations of the present study merit consideration. First, no randomization was performed, resulting in non-even numbers of cases in the standard ablation and CF-sensing technology groups. Due to the rapid and wide-spread uptake of CF-sensing catheters in complex cardiac ablation procedures, it is however unclear whether a randomized study assessing this topic will ever be performed. Secondly, this is a retrospective analysis with all ensuing limitations. Thirdly, the exclusions of patients with only clinical, but no Holter recording follow-up might have introduced a bias towards lower success rates due to over-representation of failures. This approach however was chosen to have a stringent methodology and should not have affected the comparison of catheter types. Fourthly, despite being the largest study assessing the impact of CF-sensing technology on catheter ablation of ventricular arrhythmias so far, our sample size might still have been inadequate to detect small differences between the two technologies. However, such small differences, even if they may reach statistical significance in larger trials, most probably would not have practical significance. Fifthly, our median follow-up until assessment of sustained success was 2.3 months. Accordingly, we cannot comment on late recurrences beyond this time point. Sixthly, the ablation index for optimization of lesion titration was only introduced at the very end or after the study in most of the participating centres. Its use might have improved the results in the CF-sensing group.
Conclusion
The use of CF-sensing catheters as opposed to standard ablation catheters is not associated with increased success rate nor decreased complication rate in idiopathic outflow tract PVC ablation.
Acknowledgements
We wish to thank Christine Franzini, MD, and Roger Dillier, MD (both Triemli Hospital, Zurich), Francois Regoli, MD/PhD, and Maria Luce Caputo, MD/PhD (both Cardiocentro Lugano), for their support and all the EP physicians and EP laboratory staff in all the participating hospitals for their most valuable efforts.
Funding
This work was supported by research grants from the Goldschmidt-Jacobson Foundation and the Cardiovascular Research Foundation Basel.
Conflict of interest: T.R. has received speaker/consulting honoraria or travel support from Abbott/SJM, Astra Zeneca, Brahms, Bayer, Biosense-Webster, Biotronik, Boston-Scientific, Daiichi Sankyo, Medtronic, Pfizer-BMS, and Roche, all for work outside the submitted study. He has received support for his institution’s fellowship program from Abbott/SJM, Biosense-Webster, Biotronik, Boston-Scientific, and Medtronic for work outside the submitted study. S.H.B. has received research support from Biosense-Webster and travel grants from Biosense Webster and Boston-Scientific all for work outside the submitted study. E.P. has received funding from the Swiss National Science Foundation grant; travel support from Biosense Webster. P.A. has research and educational grants from Biosense-Webster and Medtronic and lecture fees from Medtronic, Biotronik, Astra, Sanofi, and Novartis all for work outside the submitted study. B.B. has received consultant fees from Biosense Webster and Boston Scientific; Speaker fees from Biosense Webster, St. Jude Medical, and Boston Scientific. R.K. has received institutional grants form Abbott, Biosense-Webster, Biotronik, Boston-Scientific, Medtronic, and Sis-Medical for work outside the submitted study. L.H. has received institutional grants from Abbott, Abiomed, Amgen, Astra Zeneca, Bayer, Biosense Webster, Biotronik, Boston Scientific, Bracco, B. Braun, Daiichi-Sankyo, Edwards, Medtronic, MicroPort, Novartis, Vascular Medical, and Zoll. A.M. has received fellowship and training support from Biotronik, Boston Scientific, Medtronic, Abbott/St. Jude Medical, and Biosense Webster and speaker and/or consultant honoraria from Biosense Webster, Medtronic, Abbott/St. Jude Medical, AstraZeneca, Daiichi Sankyo, Biotronik, and MicroPort all for work outside of this Study. M.N. received consultant fees and travel grants from Boston Scientific, Biotronik, and Biosense-Webster. D.S. has received funding from the Swiss National Science Foundation grant; consultant fees from Biosense Webster, Biotronik, St. Jude Medical, and Boston Scientific; research grants from Biosense Webster, St. Jude Medical, and Boston Scientific via the Cardiology Division; speaker Board member fees from Biosense Webster, St. Jude Medical, and Boston Scientific. A.A. is a consultant to Boston Scientific, Backbeat, Biosense Webster, Cairdac, Corvia, EPD-Philips, Microport CRM, Philips, and Radcliffe Publisher. He received speaker fees from Boston Scientific, Medtronic, and Microport. He participates in clinical trials sponsored by Boston Scientific, EPD-Philips, Medtronic, and Philips. He has intellectual properties with Boston Scientific, Biosense Webster, and Microport CRM. The spouse of J.S. is an employee of Boston Scientific. L.R. has received speaker/consulting honoraria from Abbott/SJM and Medtronic. M.K. reports grants from the Swiss National Science Foundation, Swiss Heart Foundation, Bayer, Pfizer BMS, Boston Scientific, personal fees from Bayer, Böhringer Ingelheim, Pfizer BMS, Daiichi Sankyo, Medtronic, Biotronik, Boston Scientific, Johnson & Johnson all outside the submitted work. C.S. reports grants from Biosense-Webster and lecture fees from Abbott, Medtronic, Biosense-Webster, Boston Scientific, Microport, and Biotronik. The rest of the authors report no conflicts of interest. No commercial entities participated in this study.
Data availability
The data underlying this article cannot be shared publicly due to privacy of individuals that were investigated in the study. The data will be shared on reasonable request to the corresponding author provided that this in accordance with the institutional ethical guidelines as well as regulation and legislation.
