Strategies to improve atrioventricular synchrony in patients with a Micra AV leadless pacemaker.

The second generation of transcatheter pacing systems, called Micra AV, can provide atrioventricular (AV) synchronous pacing via a new pacing algorithm relying on sensing mechanical atrial contraction. Several novel programming parameters were introduced to enable AV synchronous pacing, including an A3 window and A4 window as well as a conduction mode switch and an activity mode switch. In addition to several automated features, manual programming optimization of some of the novel parameters is key to improving AV synchrony. A solid knowledge of the features and their programming is essential for electrophysiologists implanting or following patients with Micra AV devices. Differences in programming optimization might partially explain the high variability of AV synchrony published in real-world data reports. This article reviews the key programming parameters of Micra AV. Subsequently, optimal programming recommendations for defined patient profiles are presented. Those were established by consensus within an expert panel comprised of 11 European electrophysiologists from high-volume Micra AV centres. The patient profiles were (1) high degree AV block and slow sinus rhythm; (2) high degree AV block and fast sinus rhythm; and (3) intermittent AV block. The panel recommended to evaluate the mechanical atrial activity on transthoracic echocardiography prior to implant. It was also agreed that Auto A3 Threshold and Tracking Check should be turned off in all patients, AV conduction mode switch should be turned off in all patients with high degree AV block, and the lower rate should be programmed to 50 bpm with exceptions based on individual clinical assessment. Future studies will be useful to evaluate the strength of those recommendations to improve the AV synchrony.

Leadless pacemakers at 5-year follow-up: the Micra transcatheter pacing system post-approval registry.

BACKGROUND AND AIMS: Prior reports have demonstrated a favourable safety and efficacy profile of the Micra leadless pacemaker over mid-term follow-up; however, long-term outcomes in real-world clinical practice remain unknown. Updated performance of the Micra VR leadless pacemaker through five years from the worldwide post-approval registry (PAR) was assessed. METHODS: All Micra PAR patients undergoing implant attempts were included. Endpoints included system- or procedure-related major complications and system revision rate for any cause through 60 months post-implant. Rates were compared through 36 months post-implant to a reference dataset of 2667 transvenous pacemaker patients using Fine-Gray competing risk models. RESULTS: 1809 patients were enrolled between July 2015 and March 2018 and underwent implant attempts from 179 centres in 23 countries with a median follow-up period of 51.1 months (IQR: 21.6-64.2). The major complication rate at 60 months was 4.5% [95% confidence interval (CI): 3.6%-5.5%] and was 4.1% at 36 months, which was significantly lower than the 8.5% rate observed for transvenous systems (HR: .47, 95% CI: .36-.61; P < .001). The all-cause system revision rate at 60 months was 4.9% (95% CI: 3.9%-6.1%). System revisions among Micra patients were mostly for device upgrades (41.2%) or elevated thresholds (30.6%). There were no Micra removals due to infection noted over the duration of follow-up. At 36 months, the system revision rate was significantly lower with Micra vs. transvenous systems (3.2% vs. 6.6%, P < .001). CONCLUSIONS: Long-term outcomes with the Micra leadless pacemaker continue to demonstrate low rates of major complications and system revisions and an extremely low incidence of infection.

Utility of a guiding catheter for conduction system pacing: An early multicenter experience.

Background: Conduction system pacing (CSP), either as His bundle pacing (HBP) or as left bundle branch area pacing (LBBAP), may be superior to right ventricular apical or septal pacing. Objective: The study sought to present acute results for a new guiding catheter (Biotronik Selectra 3D) designed for CSP implantations of a retractable screw-in lead (Biotronik Solia S). Methods: The primary endpoint of the prospective, international nonrandomized BIO|MASTER.Selectra 3D study was freedom from catheter-related serious adverse device effects (SADEs) within 1 week of lead implantation. Results: Of 157 enrolled patients, CSP was achieved in 147 (93.6%) patients. No SADEs occurred within 7 days. LBBAP was achieved in 82 patients (45 as crossover from an HBP attempt) and HBP in 65 (44.2%) patients. In centers considering both HBP and LBBAP, the CSP implantation success approached 99%. Successful CSP implantations lasted on average ∼50 minutes (fluoroscopy ∼6 minutes). Most procedures (87.9%) needed only 1 catheter, even after switch from HBP to LBBAP. The catheter's handling was rated largely positive. In patients without bundle branch block, mean QRS duration increased from 106 ms (intrinsic) to 122 ms (CSP) (P = .001). In patients with bundle branch block, mean QRS duration decreased from 151 ms (intrinsic) to 137 ms (CSP) (P = .004). Conclusion: The Selectra 3D catheter is a valuable tool for HBP and LBBAP implantations of the stylet-supported pacemaker leads. When implanters considered both HBP and LBBAP, the success rate was ∼99%. Flexibility to change between different approaches may be advisable in heterogeneous and challenging areas, such as CSP implantations.

The clinical and economic impact of extended battery longevity of a substernal extravascular implantable cardioverter defibrillator.

INTRODUCTION: The extravascular implantable cardioverter defibrillator (EV ICD) has extended projected battery longevity compared to the subcutaneous implantable cardioverter defibrillator (S-ICD). This study used modeling to characterize the need for generator changes, long-term complications, and overall costs for both the EV ICD and S-ICD in healthcare systems of various countries. METHODS: Battery longevity data were modeled using a Markov model from averages reported in device labeling for the S-ICD and with engineering estimates based on real life usage from EV ICD Pivotal Study patient data to introduce variability. Clinical demographic data were derived from published literature. The primary outcomes were defined as the number of generator replacement surgeries, complications, and total healthcare system costs due to battery depletion over the expected lifetime of patients receiving EV ICD or S-ICD therapy. RESULTS: Average modeled battery longevity was determined to be 7.3 years for the S-ICD versus 11.8 years for the EV ICD. The probability of a complication after a replacement procedure was 1.4%, with an operative mortality rate of 0.02%. The use of EV ICD was associated with 1.4-1.6 fewer replacements on average over an expected patient lifetime as compared to S-ICD and a 24.3%-26.0% reduction in cost. A one-way sensitivity analysis of the model for the US healthcare system found that use of an EV ICD resulted in a reduction in replacement surgeries of greater than 1 (1.1-1.6) along with five-figure cost savings in all scenarios ($18 602-$40 948). CONCLUSION: The longer projected battery life of the EV ICD has the potential to meaningfully reduce long-term morbidity and healthcare resources related to generator changes from the perspective of multiple diverse healthcare systems.

Subcutaneous Implantable Cardioverter-Defibrillators in Patients With Congenital Heart Disease.

BACKGROUND: Very few data have been published on the use of subcutaneous implantable cardioverter-defibrillators (S-ICDs) in patients with congenital heart disease (CHD). OBJECTIVES: The aim of this study was to analyze outcomes associated with S-ICDs in patients with CHD. METHODS: This nationwide French cohort including all patients with an S-ICD was initiated in 2020 by the French Institute of Health and Medical Research. Characteristics at implantation and outcomes were analyzed in patients with CHD. RESULTS: From October 12, 2012, to December 31, 2019, among 4,924 patients receiving an S-ICD implant in 150 centers, 101 (2.1%) had CHD. Tetralogy of Fallot, univentricular heart, and dextro-transposition of the great arteries represented almost one-half of the population. Patients with CHD were significantly younger (age 37.1 ± 15.4 years vs 50.1 ± 14.9 years; P < 0.001), more frequently female (37.6% vs 23.0%; P < 0.001), more likely to receive an S-ICD for secondary prevention (72.3% vs 35.9%; P < 0.001), and less likely to have severe systolic dysfunction of the systemic ventricle (28.1% vs 53.1%; P < 0.001). Over a mean follow-up period of 1.9 years, 16 (15.8%) patients with CHD received at least 1 appropriate shock, with all shocks successfully terminating the ventricular arrhythmia. The crude risk of appropriate S-ICD shock was twice as high in patients with CHD compared with non-CHD patients (annual incidences of 9.0% vs 4.4%; HR: 2.1; 95% CI: 1.3-3.4); however, this association was no longer significant after propensity matching (especially considering S-ICD indication, P = 0.12). The burden of all complications (HR: 1.2; 95% CI: 0.7-2.1; P = 0.4) and inappropriate shocks (HR: 0.9; 95% CI: 0.4-2.0; P = 0.9) was comparable in both groups. CONCLUSIONS: In this nationwide study, patients with CHD represented 2% of all S-ICD implantations. Our findings emphasize the effectiveness and safety of S-ICD in this particularly high-risk population. (S-ICD French Cohort Study [HONEST]; NCT05302115).

Comparison of first- and second-generation leadless pacemakers in patients with sinus rhythm and complete atrioventricular block.

INTRODUCTION: The efficacy and safety of leadless cardiac pacemakers (LPMs) as an alternative to conventional transvenous cardiac pacing have been largely reported. The first generation of the MicraTM transcatheter pacing system (VR; Medtronic) was able to provide single-chamber VVI(R) pacing mode only, with a potential risk of pacemaker syndrome in sinus rhythm patients. A second-generation system (AV) now provides atrioventricular synchrony through atrial mechanical (Am) sensing capability (VDD mode). OBJECTIVE: We sought to compare VR and AV systems in sinus rhythm patients with chronic ventricular pacing (Vp) for complete atrioventricular block. METHODS: All consecutive patients implanted with an LPM in our department for complete atrioventricular block were retrospectively screened. Patients with atrial fibrillation, sinus dysfunction, or Vp burden <20% at 1 month postimplantation were excluded. Patients were systematically followed with a visit at 1 month, and then at least once a year. RESULTS: A total of 93 patients-45 VR (2015-2020) and 48 AV (2020-2021)-were included. VR and AV patients had similar baseline characteristics, except for VR patients being older (80 ± 8 vs. 77 ± 9 years, p = 0.049). The mean Vp burden was 77% in the VR and 82% in the AV group (p = 0.38). In AV patients, the median AV synchronous beats rate was 78%, with 65% having a >66% rate. An E/A ratio <1.2 as measured on echocardiography was the only independent predictor of accurate atrial mechanical tracking (p = 0.01). One-year survival rate was similar in both groups. Five patients in the VR and 0 in the AV group eventually developed pacemaker syndrome within 1 year post-implantation (p = 0.02). CONCLUSION: In sinus rhythm patients with chronic Vp for complete atrioventricular block implanted with an LPM, the atrial mechanical sensing algorithm allowed significant atrioventricular synchrony in most patients and was associated with no occurrence of-otherwise rare-pacemaker syndrome.

Leadless cardiac pacing: Results from a large single-centre experience.

BACKGROUND: The efficacy and safety of leadless cardiac pacing as an alternative to conventional transvenous cardiac pacing in selected patients have been widely reported. AIM: To report the experience of a high-volume implantation centre with older and new generations of leadless pacemakers. METHODS: This retrospective observational study included the first consecutive 400 patients who underwent implantation of a leadless pacemaker in our centre. Complications and electrical parameters were evaluated during follow-up, comparing patients implanted with first-generation (Micra™ VR) and second-generation (Micra™ AV) leadless pacemakers (Medtronic, Minneapolis, MN, USA). Data were collected by a review of medical files. RESULTS: Among 400 procedures, there were 328 Micra™ VR pacemakers and 72 Micra™ AV pacemakers implanted, followed for a median of 16 months (694 patient-years). The mean age was 77 years and both groups had a high burden of co-morbidities. Implantation success rate was 99.5%. A total of 87.5% of patients were discharged the day after the procedure. The pacing threshold remained stable and<2V in 96.5% of all patients. The perioperative complication rate at 30 days was 3.5%. Outcomes were similar between the two groups. CONCLUSION: Leadless cardiac pacing is a safe and efficient alternative to conventional transvenous cardiac pacing.

Clinical Phenotypes and Atrial Fibrillation Recurrences After Catheter Ablation: An Unsupervised Cluster Analysis.

Catheter ablation (CA) is a well-established treatment of atrial fibrillation (AF). Data-driven cluster analysis is able to better distinguish prognostically-relevant phenotype clusters among patients with AF. We performed a hierarchical cluster analysis in a cohort of AF patients undergoing a first CA and evaluate associations between identified clusters and recurrences of arrhythmia following ablation. The study included 209 AF patients treated with CA. A total of 3 clusters with distinct characteristics were identified. Recurrences at 1 year occurred in 27.2% in Cluster 1, 43.2% in Cluster 2 and 60.9% in Cluster 3 (P < 0.0001). Cluster classification was independently associated with arrhythmia recurrences (HR 1.58, 95% CI 1.01-2.49, P = 0.046) after adjustment for age, CHA2DS2-VASc score, left atrial volume, type of atrial fibrillation and ejection fraction. To concluded, cluster analysis identified 3 statistically-driven groups among AF patients treated with CA with different risks for arrhythmia recurrences.

T Waves May Not Be What They Seem!

A 39-year-old women who received a transvenous dual-chamber pacemaker in childhood developed 20 years later severe tricuspid valve stenosis induced by the leads and worsened by a pseudo-pacemaker syndrome. (Level of Difficulty: Intermediate.).

A leadless pacemaker in the real-world setting: Patient profile and performance over time.

Background: While prior Micra trials demonstrated a high implant success rate and favorable safety and efficacy results, changes in implant populations and safety over time is not well studied. The objective of this analysis was to report the performance of Micra in European and Middle Eastern patients and compare to the Micra Investigational Device Exemption (IDE) and Micra Post Approval Registry (PAR) studies. Methods: The prospective, single-arm Micra Acute Performance European and Middle Eastern (MAP EMEA) registry was designed to further study the performance of Micra in patients from EMEA. The primary endpoint was to characterize acute (30-day) major complications. Electrical performance was analyzed. The major complication rate through 12 months was compared with the IDE and PAR studies. Results: The MAP EMEA cohort (n = 928 patients) had an implant success rate of 99.9% and were followed for an average of 9.7 ± 6.5 months. Compared to prior studies, MAP EMEA patients were more likely to have undergone dialysis and have a condition which precluded the use of a transvenous pacemaker (p < .001). Within 30 days of implantation, the MAP EMEA cohort had a major complication rate of 2.59%. Mean pacing thresholds were low and stable through 12 months (0.61 ± 0.40 V at 0.24 ms at implant and 12 months). Through 12 months post-implantation, the major complication rate for MAP EMEA was not significantly different from IDE (p = .56) or PAR (p = .79). Conclusion: Despite patient differences over time, the Micra leadless pacemaker was implanted with a high success rate and low complication rate, in-line with prior reports.

Recurrences of Atrial Fibrillation Despite Durable Pulmonary Vein Isolation: The PARTY-PVI Study.

BACKGROUND: Recurrences of atrial fibrillation (AF) after pulmonary vein isolation (PVI) are mainly due to pulmonary vein reconnection. However, a growing number of patients have AF recurrences despite durable PVI. The optimal ablative strategy for these patients is unknown. We analyzed the impact of current ablation strategies in a large multicenter study. METHODS: Patients undergoing a redo ablation for AF and presenting durable PVI were included. The freedom from atrial arrhythmia after pulmonary vein-based, linear-based, electrogram-based, and trigger-based ablation strategies were compared. RESULTS: Between 2010 and 2020, 367 patients (67% men, 63±10 years, 44% paroxysmal) underwent a redo ablation for AF recurrences despite durable PVI at 39 centers. After durable PVI was confirmed, linear-based ablation was performed in 219 (60%) patients, electrogram-based ablation in 168 (45%) patients, trigger-based ablation in 101 (27%) patients, and pulmonary vein-based ablation in 56 (15%) patients. Seven patients (2%) did not undergo any additional ablation during the redo procedure. After 22±19 months of follow-up, 122 (33%) and 159 (43%) patients had a recurrence of atrial arrhythmia at 12 and 24 months, respectively. No significant difference in arrhythmia-free survival was observed between the different ablation strategies. Left atrial dilatation was the only independent factor associated with arrhythmia-free survival (HR, 1.59 [95% CI, 1.13-2.23]; P=0.006). CONCLUSIONS: In patients with recurrent AF despite durable PVI, no ablation strategy used alone or in combination during the redo procedure appears to be superior in improving arrhythmia-free survival. Left atrial size is a significant predictor of ablation outcome in this population.

Dual-chamber ICD for left bundle branch area pacing: the cardiac resynchronization and arrhythmia sensing via the left bundle (cross-left) pilot study.

BACKGROUND: Left bundle branch area pacing (LBBAP) has emerged as a promising technique to deliver cardiac resynchronization therapy (CRT). However, safety and efficacy of ventricular arrhythmia sensing via the left bundle in implantable cardioverter-defibrillator (ICD) recipients remain unclear. We sought to evaluate the feasibility of a single LBBAP lead connected to a dual-chamber ICD in patients indicated with a CRT-D implantation. METHODS: The CROSS-LEFT pilot study prospectively included 10 consecutive patients with a reduced ejection fraction and a complete left bundle branch block, indicated with a prophylactic CRT-D. A DF-1 lead was implanted at the right ventricular (RV) apex, and an LBBAP lead through the interventricular septum. Ventricular fibrillation was induced at implantation in both conventional (RV) and left bundle branch area sensing configurations. The latter was the final sensing configuration, and patients were implanted with a dual-chamber DF-1 ICD connected to the atrial lead (RA port), the LBBAP lead (RV IS-1 port), and the defibrillation lead (RV DF-1 port), the IS-1 pin being capped. Atrioventricular delay was optimized to ensure fusion between LBBAP and native conduction from the right bundle. Patients were followed during 6 months. RESULTS: No difference between both configurations was observed regarding R-wave sensing in sinus rhythm (p = 0.22), ventricular fibrillation median interval detection (p = 1.00), or total induced episode duration (p = 0.78). LBBAP resulted in a significant reduction of median QRS width from 164 to 126 ms (p = 0.002). Median ventricular sensing significantly improved from 9.7 at implantation to 18.8 mV at 6 months (p = 0.01). Median LVEF also significantly improved from 29 to 44% at 6 months (p = 0.002). CONCLUSION: Ventricular arrhythmia sensing and defibrillation can be performed via a single LBBAP lead connected to a dual-chamber ICD, and is associated with significant electromechanical reverse remodeling. CLINICAL TRIAL REGISTRATION NUMBER: NCT05102227 In patients presenting with left bundle branch block and left ventricular systolic dysfunction, a left bundle branch area pacing lead connected to a DF-1 dual-chamber implantable cardioverter-defibrillator provides safe ventricular arrhythmia sensing and efficient electro-mechanical resynchronization.

Implantation of a leadless pacemaker in young adults.

AIMS: Leadless pacing has emerged as an alternative to conventional transvenous pacemakers to mitigate the risks of pocket- and lead-related complications but its use remains controversial in young adults mostly because experience in this patient population is limited. We sought to examine the feasibility and safety of implanting leadless single chamber pacemakers in young adults. METHODS: This multicenter, retrospective, observational study sought to evaluate the safety, efficacy, and electrical performance of the Micra VR Transcatheter Pacemaker System (Medtronic) in patients between 18 and 40 years who underwent implantation of a leadless pacemaker for any indication at the university medical centers of Bordeaux, Clermont-Ferrand, Toulouse, and Tours (France), between 2015 and 2021. The primary safety endpoint was freedom from system-related or procedure-related major complications at 6 months. The primary efficacy endpoint was the combination of a low (≤2 V) and stable (increase within 1.5 V) pacing capture threshold at 6 months. RESULTS: Leadless pacemaker implantation was successful in all 35 patients. At 6 months, safety endpoint was met for 35 (100%) and efficacy endpoint for 34 (97%) patients. During a follow-up of 26 ± 15 months (range: 6-60 months), Safety endpoint remained 100% and efficacy endpoint was 94%. Leadless pacemaker retrieval was not required in any patient. Approximately one-third of patients (n = 13, 37%) had >40% ventricular pacing burdens at 1 year, including all 10 patients with a complete AV block but also 3 patients with normal AV conduction during implantation. One patient reported symptoms of pacemaker syndrome which was confirmed using Holter recording and successfully treated using reprogramming. CONCLUSION: In this observational study, leadless pacemakers demonstrated favorable short- and intermediate-term safety and effectiveness in young adults.

CRT-D replacement strategy: results of the BioCONTINUE study.

BACKGROUND: In patients with cardiac resynchronization therapy defibrillators (CRT-Ds), the need for implantable cardioverter-defibrillator (ICD) back-up may be questionable at time of CRT-D replacement (REP) if ICD implant criteria are no longer met due to an improved left ventricular ejection fraction (LVEF) and if no major ventricular arrhythmic event (VAE) occurred during the CRT-D lifetime. The aim of our study was to assess the relevance of ICD back-up and predictors of VAE after REP in primary prevention CRT-D patients. METHODS: The prospective, observational, international BioCONTINUE study investigated the rate of patients with at least 1 sustained VAE (sVAE) post-REP and searched for predictive factors of sVAE. RESULTS: Two hundred seventy-six patients (70 ± 10 years, 77% men, mean LVEF 40.6 ± 12.6%) were followed for 28.4 ± 10.2 months. The rate of patients with sVAE was 8.3%, 10.3%, and 21.2% at 1, 2, and 4 years post-REP. Patients without persistent ICD indication at REP still had a sVAE rate of 5.7% (95% CI 2.3-11.5%) at 2 years. In multivariate analysis, predictive factors of subsequent sVAE were (i) persistent ICD indication (hazard ratio (HR) 3.6; 95% CI 1.6-8.3; p = 0.003); (ii) 64-72 years of age as compared to ≥ 79 years (HR 3.7; 95% CI 1.4-9.7; p = 0.008); and (iii) ischemic heart disease (HR 4.4; 95% CI 2.1-9.3; p < 0.0001). CONCLUSIONS: The risk of sVAE (21.2% at 4 years post-REP) depends on age, ischemic heart disease, and ICD indication at the time of REP. A non-trivial risk of sVAE remains in patients without persistent ICD indication. CLINICAL TRIAL REGISTRATION: NCT02323503.

Leadless or Conventional Transvenous Ventricular Permanent Pacemakers: A Nationwide Matched Control Study.

Background Leadless ventricular permanent pacemakers (leadless VVI or LPM) were designed to reduce lead-related complications of conventional VVI pacemakers (CPM). The aim of our study was to assess and compare real-life clinical outcomes within the first 30 days and during a midterm follow-up with the 2 techniques. Methods and Results This French longitudinal cohort study was based on the national hospitalization database. All adults (age ≥18 years) hospitalized in French hospitals from January 1, 2017 to September 1, 2020, who underwent a first LPM or CPM were included. The study included 40 828 patients with CPM and 1487 with LPM. After propensity score matching 1344 patients with CPM were matched 1:1 with patients treated with LPM. Patients with LPM had a lower rate of all-cause and cardiovascular death within the 30 days after implantation. During subsequent follow-up (mean: 8.6±10.5 months), risk of all-cause death in the unmatched population was significantly higher in the LPM group than in the CPM group, whereas risk of cardiovascular death and of endocarditis was not significantly different. After matching on all baseline characteristics including comorbidities (mean follow-up 6.2±8.7 months), all-cause death, cardiovascular death, and infective endocarditis were not statistically different in the 2 groups. Conclusions Patients treated with leadless VVI pacemakers had better clinical outcomes in the first month compared with the patients treated with conventional VVI pacing. During a midterm follow-up, risk of all-cause death, cardiovascular death, and endocarditis in patients treated with leadless VVI pacemaker was not statistically different after propensity score matching.

Does sports participation increase risk in patients with long QT syndrome? Results from a large French cohort.

AIMS: Sports practice, especially in competition, is usually restrained in patients diagnosed with long QT syndrome (LQTS). Although data are scarce, a low incidence of cardiac arrhythmic events (CAEs) during sports practice is reported. We aim to evaluate the incidence of CAE during sports practice in LQTS patients. METHODS AND RESULTS: All consecutive patients above 18 years of age diagnosed with LQTS and prospectively followed at the referral centre for inherited arrhythmia syndrome received a survey to retrospectively assess their sports practice prior to and after the diagnosis of LQTS. Two hundred and forty-six patients were included (57% females). The median age was 43 years, and the median QTc was 457 ms (428; 482). Patients reported a total of 4092 years [1376 (34%) after diagnosis] of sports practice: 2905 (77%) [1138 (39%) after diagnosis] years of leisure practice and 1187 (23%) [238 (20%) after diagnosis] years of competitive practice. One hundred and eighty (73%) patients practiced sport prior to the diagnosis of LQTS and 170 (69%) after. Prior to the diagnosis, four (2%) patients presented a CAE during leisure sports practice and one during competition. After diagnosis, only one patient presented a CAE, appropriately treated by an implantable cardioverter defibrillator discharge, in the context of beta-blocker non-compliance. The CAE event rate was 0.0007 events/year in the 1376 years of total sports practice after the diagnosis of LQTS. CONCLUSION: After the diagnosis of LQTS, the occurrence of CAE is very low during sports practice, even in competitive practice. There was no CAE in patients properly treated with beta-blocker therapy with good compliance.

Efficacy and Safety of an Extravascular Implantable Cardioverter-Defibrillator.

BACKGROUND: The extravascular implantable cardioverter-defibrillator (ICD) has a single lead implanted substernally to enable pause-prevention pacing, antitachycardia pacing, and defibrillation energy similar to that of transvenous ICDs. The safety and efficacy of extravascular ICDs are not yet known. METHODS: We conducted a prospective, single-group, nonrandomized, premarket global clinical study involving patients with a class I or IIa indication for an ICD, all of whom received an extravascular ICD system. The primary efficacy end point was successful defibrillation at implantation. The efficacy objective would be met if the lower boundary of the one-sided 97.5% confidence interval for the percentage of patients with successful defibrillation was greater than 88%. The primary safety end point was freedom from major system- or procedure-related complications at 6 months. The safety objective would be met if the lower boundary of the one-sided 97.5% confidence interval for the percentage of patients free from such complications was greater than 79%. RESULTS: A total of 356 patients were enrolled, 316 of whom had an implantation attempt. Among the 302 patients in whom ventricular arrhythmia could be induced and who completed the defibrillation testing protocol, the percentage of patients with successful defibrillation was 98.7% (lower boundary of the one-sided 97.5% confidence interval [CI], 96.6%; P<0.001 for the comparison with the performance goal of 88%); 299 of 316 patients (94.6%) were discharged with a working ICD system. The Kaplan-Meier estimate of the percentage of patients free from major system- or procedure-related complications at 6 months was 92.6% (lower boundary of the one-sided 97.5% CI, 89.0%; P<0.001 for the comparison with the performance goal of 79%). No major intraprocedural complications were reported. At 6 months, 25 major complications were observed, in 23 of 316 patients (7.3%). The success rate of antitachycardia pacing, as assessed with generalized estimating equations, was 50.8% (95% CI, 23.3 to 77.8). A total of 29 patients received 118 inappropriate shocks for 81 arrhythmic episodes. Eight systems were explanted without extravascular ICD replacement over the 10.6-month mean follow-up period. CONCLUSIONS: In this prospective global study, we found that extravascular ICDs were implanted safely and were able to detect and terminate induced ventricular arrhythmias at the time of implantation. (Funded by Medtronic; ClinicalTrials.gov number, NCT04060680.).