The subcutaneous implantable cardioverter-defibrillator (S-ICD) was developed to reduce complications associated with transvenous leads while preserving efficacy in terminating malignant ventricular arrhythmias. However, current evidence supporting the S-ICD is primarily derived from industry-sponsored studies and highly specialized centers. This study aims to offer a comprehensive, nationwide, real-world assessment of all patients who underwent S-ICD implantation in France. The HONEST (coHOrte fraNcaise des dEfibrillateurs Sous cuTanés) cohort is a French nationwide, single-arm, observational ongoing study that enrolled all patients who underwent implantation of an S-ICD (EMBLEM, Boston Scientific) between October 2012 (the first implantation in France) and December 2019. Clinical endpoints are centrally adjudicated. Overall, 4,924 (77% males; 49.9 years) patients, representing 98.2% of all S-ICD implantations during the study period in France, were included. The HONEST study represents the first nationwide cohort evaluating S-ICD recipients to provide contemporary, real-world data. Its goal is to identify areas for improvement and refine strategies to prevent sudden cardiac death. (S-ICD French Cohort Study [HONEST]; NCT05302115)

BACKGROUND AND AIMS:Although use of the subcutaneous implantable cardioverter defibrillator (S-ICD) is increasing, evidence from industry-independent and unselected populations remains limited. METHODS:HONEST is a ongoing nationwide academic observational study enrolling 98.2% of patients implanted with an S-ICD across France (2012-2019). Five-year clinical endpoints were centrally adjudicated. RESULTS:Overall, 4924 patients were enrolled (mean age 49.9 ± 15 years, 76.7% male, 63.0% for primary prevention). Implants used general anaesthesia (78.9%), and defibrillation testing (82.6%). Perioperative complications (within 30 days) occurred in 4.4%. At 5 years, cumulative incidence rates were 13.8% for inappropriate shocks, 10.8% for early battery depletion, 2.4% for infections, 1.5% for lead dysfunction, and 1.4% for chronic discomfort. Reoperation was required in 16.9%, need for cardiac pacing in 3.1%, and definite S-ICD extraction in 8.4%. Inappropriate shocks were independently associated with male sex (hazard ratio [HR] 1.29, 95% confidence interval [CI] 1.14-1.46, P < .001), obesity (HR 1.35, 95% CI 1.02-1.79, P = .032), arrhythmogenic right ventricular cardiomyopathy (HR 1.70, 95% CI 1.03-2.81, P = .036), and the presence of a pacemaker (HR 2.20, 95% CI 1.16-4.17, P = .016). SMART Pass filtering significantly reduced inappropriate shocks (HR 0.67, 95% CI 0.50-0.89, P = .007). Among patients with inappropriate shocks, ∼1% developed induced ventricular fibrillation (one fatality), and 10% underwent device extraction. Ineffective shocks or undetected arrhythmias occurred in only 0.2%. Among 547 deaths (11.1%), 53.9% were cardiovascular, including 26 sudden deaths, and 8 were S-ICD/procedure-related, with none related to S-ICD extraction. CONCLUSIONS:This nationwide study refines the long-term event profile of S-ICD therapy and may inform clinical practice and device selection.

BACKGROUND AND AIMS:Current evidence on catheter ablation for patients with congenital heart disease (CHD) is derived from small, retrospective studies. This study aims to provide insights from a nationwide contemporary registry. METHODS:This prospective study included all CHD patients referred for catheter ablation from 2020 to July 2024 across 28 French centres. The primary outcome was the rate of per-procedural acute success. Secondary outcomes included complications as well as freedom from arrhythmia recurrence. RESULTS:A total of 1135 consecutive catheter ablation procedures were performed in 998 patients (mean age 46.1 ± 16 years, 55.5% male). The main primary clinical arrhythmias targeted were atrial flutter/tachycardia in 677 (59.6%), atrial fibrillation in 195 (17.2%), ventricular arrhythmia in 188 (16.6%), and atrioventricular reentrant tachycardia in 38 (3.3%), with significant variations in patterns observed based on the underlying substrate. Clinical arrhythmia was successfully ablated in 1071 patients (94.4%). The mean number of arrhythmias targeted per procedure was 1.5 ± 0.7, with overall acute success rates exceeding 90% for all arrhythmias except for ventricular arrhythmias (86.7%). Acute complication occurred in 43 procedures (3.8%), including 1 (0.1%) death. The overall 1- and 2-year recurrence-free rates were 77.3% (95% confidence interval 74.2%-80.4%) and 68.4% (95% confidence interval 64.7%-72.3%), respectively. Significant variations in recurrence rates were noted based on the type of arrhythmia and the underlying CHD. CONCLUSIONS:Catheter ablation in patients with CHD demonstrates highly favourable acute outcomes and a low complication rate. Recurrence rates during follow-up vary depending on the targeted arrhythmia and the underlying CHD. These findings should be considered in the benefit-risk assessment.

Background Recurrence rates of atrial arrhythmias after catheter ablation in patients with congenital heart disease (CHD) remain substantial. Given the high prevalence of peritricuspid flutter, systematic cavotricuspid isthmus (CTI) ablation may represent a rational preventive strategy. Objectives The objective of this study was to assess the impact of empirical CTI ablation in CHD patients. Methods This prospective nationwide study included all CHD patients referred for a first catheter ablation of an atrial arrhythmia between 2020 and 2024. Empirical ablation comprised probabilistic (noninducible arrhythmia with prior documentation) and prophylactic (no prior documentation) ablation. The primary endpoint was freedom from any atrial arrhythmia recurrence. Secondary endpoints included arrhythmia-related hospitalizations, redo ablations, and complications. Results Among 575 patients undergoing a first catheter ablation for atrial arrhythmia, 345 (60.0%) had CTI-dependent flutter. The remaining 230 patients formed the study population (mean age: 48.2 ± 16.4 years; 50.9% male). CHD complexity was predominantly moderate (57.4%). Targeted arrhythmias were atrial macro-re-entry (53.0%), atrial fibrillation (47.0%), and focal atrial tachycardia (17.4%), with multiple arrhythmias in 16.5%. Empirical CTI ablation was performed in 71 patients (30.9%) and was associated with significantly higher freedom from any atrial arrhythmia at 1 year (78.1% vs 65.6%, P = 0.010) and 2 years (71.2% vs 56.1%, P = 0.025), remaining independently associated with lower risk of recurrence after multivariable adjustment (HR: 0.47, 95% CI: 0.24-0.92, P = 0.027). This benefit was primarily observed in patients without atrial fibrillation history (interaction P = 0.005). Arrhythmia-related hospitalization was also significantly reduced (14.1% vs 25.8%, P = 0.048). Conclusions Empirical CTI ablation is associated with improved freedom from atrial arrhythmia and reduced rehospitalization in CHD patients.

BACKGROUND:Evidence supporting the Micra AV leadless pacing system has largely derived from highly experienced centers, potentially limiting generalizability to routine clinical practice. METHODS:The AV-CESAR study (French Cohort Evaluating the Effectiveness of Atrioventricular Synchrony by the micRa AV) is a nationwide retrospective cohort, including the first 1000 patients implanted with a Medtronic Micra AV leadless pacemaker in France (2020-2024). Mean follow-up was 13.4±10.6 months. Primary end points were early (in-hospital) and late (postdischarge) device-related major complications; pacemaker syndrome and need for implantation of a new pacing system were centrally adjudicated. RESULTS:Among 1003 patients, device implantation was successful in 1000 (99.7%). Mean age was 72.0±15 years; 62.8% were men, 44.0% had ≥2 comorbidities, and 62.4% were unsuitable for transvenous pacemakers. The primary indication was permanent complete atrioventricular block with preserved sinus rhythm (78.0%). Early major complications occurred in 2.4%, including pericardial effusion (0.8%; 3 requiring surgery), access-site complications (0.8%), and thromboembolism (0.3%). Late major complications included pacemaker syndrome (2.5%), pacing-induced cardiomyopathy (1.2%), high thresholds (>4 V/0.24ms, 0.3%), and premature battery depletion (0.2%). No device infections or dislodgements were observed. Overall, 2.5% of patients required implantation of a new pacing system (pacing-induced cardiomyopathy n=11; pacemaker syndrome n=7; high threshold n=3; battery/software failure n=3; tricuspid regurgitation n=1) and 12.7% were permanently reprogrammed to ventricular paced/sensed, inhibited (VVI) mode. In pacing-dependent patients with ambulatory Holter monitoring (>3.4 million paced cycles), mean atrioventricular synchrony was 67.6±17.3% and correlated with device-reported AM-VP (74.8±17.1%; R2=0.92; P<0.001). Atrioventricular synchrony declined at heart rates >90 beats per minute (5.6% of monitored time). All-cause mortality was 13.8%, with 0.2% directly device-related; 41.7% of deaths were cardiovascular. CONCLUSIONS:The Micra AV system is primarily used as an alternative when dual-chamber conventional pacemakers are not feasible. It demonstrated acceptable safety and clinical performance in a high-risk population. The marked reduction in atrioventricular synchrony at higher heart rates may suggest limited clinical benefit in patients with higher exertional heart rates. REGISTRATION:URL: https://clinicaltrials.gov/study/NCT05953558; Unique identifier: NCT05953558.

BACKGROUND:The subcutaneous implantable cardioverter-defibrillator (S-ICD) is an established therapy for sudden cardiac death prevention, but sex-specific outcomes remain incompletely characterized. OBJECTIVES:This study evaluated sex-related differences in baseline characteristics, appropriate shocks, complications, reinterventions, and mortality among S-ICD recipients. METHODS:The nationwide HONEST (S-ICD French Cohort Study) cohort enrolled all patients who received an S-ICD in France between 2012 and 2019. Clinical endpoints were centrally adjudicated. Sex-specific associations with outcomes were assessed by using propensity score-based inverse probability weighting. RESULTS:Among 4,924 S-ICD recipients, 1,148 were women (23.3%). Compared with men, women were younger (47.3 ± 15.6 years vs 50.6 ± 14.7 years; P < 0.001), less frequently received an implant for primary prevention (57.6% vs 65.1%; P < 0.001), less often had coronary artery disease (38.9% vs 56.5%; P < 0.001), and more often had electrical heart disease (26.3% vs 20.4%; P < 0.001). After adjustment, women had a lower 5-year risk of appropriate shocks (HR: 0.85; 95% CI: 0.74-0.98; P = 0.023) and similar overall complication and reintervention rates but a distinct complication profile, with higher risks of chronic pain (HR: 2.63; 95% CI: 1.61-4.29; P < 0.001) and lead dislodgment (HR: 1.79; 95% CI: 1.09-2.95; P = 0.022) and a lower risk of inappropriate shocks (HR: 0.64; 95% CI: 0.50-0.82; P < 0.001). All-cause mortality was lower in women, whereas S-ICD-unresponsive sudden death and device-related mortality were similar. CONCLUSIONS:Women receiving an S-ICD experienced fewer appropriate shocks, with similar overall complication and reintervention rates, but a distinct complication profile. These findings support sex-informed S-ICD selection and follow-up. (S-ICD French Cohort Study [HONEST]; NCT05302115).

Background Heart transplantation (HTx) has been suggested for refractory electrical storm (ES). Data regarding the outcomes of these patients are scarce. Objective To compare the prognosis of refractory ES patients listed for urgent HTx, with and without transplantation. Methods Patients registered on urgent HTx waiting list for refractory ES were retrospectively included in 13 French centers between 2010–2022. The primary endpoint was in-hospital all-cause mortality. Results Eighty-five patients were included (85.9% men; 56.0 [48.0–61.0] years old; 55.1% with dilated cardiomyopathy), among whom 45 (52.9%) ultimately underwent HTx during index hospitalization. In the overall cohort, 89.3% of patients received amiodarone, 64.3% beta-blockers, 45.9% required deep sedation, 5.9% underwent stellate ganglion block, and 41.2% received mechanical circulatory support. Catheter ablation was less frequently performed in the transplanted group (20.0% vs 57.5%, p < 0.01). No difference was found for in-hospital mortality between transplanted and non-transplanted patients (28.9% vs 35.0%, HR 0.72 [0.34–1.53], p=0.0.39). After 1-year follow-up, 14 patients (16.5%) of the non-transplanted group eventually underwent HTx, with 4 of them dying subsequently. Five patients (5.9%) were removed from HTx waiting list due to functional improvement. Conversely, 14 transplanted patients (16.5%) died. Conclusion Refractory ES carries a high in-hospital mortality rate, affecting one-third of patients. Overall, 69.4% of patients listed for urgent HTx underwent transplantation, including 52.9% during index hospitalization and 16.5% within the year post-discharge, highlighting the need to optimize selection criteria and implement a comprehensive treatment that sometimes allows overcoming the acute phase, enabling HTx under more stable conditions.

AIMS:A dual-chamber leadless pacemaker (LP) system relies on a beat-to-beat, wireless, implant-to-implant (i2i™) communication between implanted devices in the right atrium and right ventricle (A-to-V and V-to-A). Atrioventricular (AV) synchrony was evaluated during an ambulatory 24 h period of daily living to determine if its effectiveness can be maintained under real-world conditions. METHODS AND RESULTS:A prospective, single-arm, multicentre clinical study (ClinicalTrials.gov identifier NCT05252702) evaluated the overall safety and performance of the dual-chamber LPs in patients with standard indications for dual-chamber pacing. Following the 3-month visit, eligible patients wore 12-lead Holter monitors for 24 h while resuming the activities of daily living while under clinically driven programmed settings. Leadless pacemaker diagnostic data were interrogated when patients returned to the clinic. An independent Holter core laboratory adjudicated the proportion of synchronous beats (PR intervals within paced and sensed AV delay bounds). Relationships between AV synchrony and i2i communication success rate, implant indication, heart rate, and AV event type were evaluated. Among 47 analysable patients, mean AV synchrony was achieved in 96.7% of beats, exceeding mean A-to-V and V-to-A transmission success rates of 93.4% and 92.1%, respectively. There were no significant differences in AV synchrony between sinus node and AV block patients. Across all AV paced/sensed cycle combinations and heart rate ranges (including >100 b.p.m.), AV synchrony was sustained >90% in an ambulatory real-world setting. CONCLUSION:A dual-chamber leadless pacing system demonstrated >96% overall AV synchrony for a 24 h period of daily living while programmed to clinically appropriate settings, thus showing that true dual-chamber DDD(R) pacing can be maintained in a real-world environment.