Reinoud Elwin Knops

Background and Aims: MODULAR ATP is an ongoing trial assessing the efficacy of a subcutaneous implantable cardioverter defibrillator (S-ICD) in communication with a leadless pacemaker (LP) that can deliver bradycardia pacing and antitachycardia pacing. The objective of this study was to assess safety and pacing performance of the investigational LP. Methods: The study enrolled patients with an ICD indication and at high risk for monomorphic ventricular tachycardia. Pacemaker dependent patients were excluded. Primary safety endpoint 2 was the percentage of patients free from major LP-related complications at 12 months. The secondary effectiveness endpoint assessed the rate response performance of the LP under workload. Parameters related to the pacing performance were also measured. Results: In 297 patients, the mean age was 59±12 years, the mean left ventricular ejection fraction was 35.3±13.1%, and 17.5% were female. LP implant was attempted in 286 patients and was successful in 100%. The major LP-related complication free rate at 12 months was 97.2% (one-sided 97.5% LCL 94.5%), surpassing the performance goal of 81%. There were no LP-related complications following Implant. For the secondary effectiveness endpoint, the slope of the normalized sensor rate versus the normalized workload was 0.96 (95% LCL 0.91, 95% UCL 1.02), within the performance goal range of 0.65-1.35. At 12 months, 96.8% of patients had a pacing capture threshold ≤ 2V @ 0.4ms pulse width. Conclusions: The performance of the modular pacing-defibrillator system at one year demonstrated a low complication rate and reliable pacing functionality.

Background: To improve survival in patients at risk of sudden cardiac death, subcutaneous ICDs (S-ICDs) require optimal implant positioning for effective shocks. Defibrillation (DF) testing is recommended but carries serious risks. The PRAETORIAN score predicts defibrillation outcomes based on chest X-rays. The PRAETORIAN-DFT trial evaluated whether omission of DF testing guided by the PRAETORIAN score is non-inferior for first-shock efficacy. Methods: In this multinational trial, S-ICD patients from 37 centers were randomized to DF testing or no DF testing. In the No-DF testing group, the PRAETORIAN score was evaluated before discharge. The primary endpoint was failed first shock for spontaneous ventricular arrhythmias, as a surrogate for defibrillation success, tested for non-inferiority with a 3% absolute risk margin. Secondary endpoints included mortality, potential DF testing-related complications, and S-ICD revisions. Results: The included 965 patients (No-DF testing, n=483;DF testing, n=482) were followed for a median of 41 months. Failed first shock for spontaneous ventricular arrhythmia occurred in 1.7% of the No-DF testing group versus 2.3% of the DF testing group (–0.6%, 95% CI [ –2.6 to 1.4]; p<0.001). There were no significant differences in all-cause mortality (HR 0.9 [95% CI 0.6–1.4]) or arrhythmic death (HR 0.4 [95% CI 0.04–3.4]). Potential DF testing-related complications occurred in 1.7% in the DF testing group. Postoperative S-ICD revisions due to inadequate positioning were identical between groups (n=2 each). Conclusions: PRAETORIAN score–guided omission of DF testing- after S-ICD implantation did not increase the risk of failed first shocks for spontaneous ventricular arrhythmias and reduced procedural risk without increasing S-ICD revisions. (Funded by Boston Scientific; PRAETORIAN-DFT).

Aims: The aim of this analysis was to evaluate the upgradeability of a single-chamber leadless pacemaker (LP) to a dual-chamber system in patients indicated for a dual-chamber pacemaker. Methods and results: A prospective, multicentre study evaluated the safety and performance of a dual-chamber LP. The study included patients with a prior ventricular LP to evaluate its upgradeability. Patients had an attempted atrial LP implant, and if successfully implanted, the LPs were paired to a dual-chamber pacing mode to evaluate upgrade success. Patients were followed for 12 months from the attempted atrial LP implantation. Among 35 patients with an attempted upgrade (62.9% male, average age 70 years), the most common primary indication was sinus node dysfunction (57.1%). Out of 35 patients, 91.4% had successful upgrades. The mean atrial device electrical measurements stabilized within 1 month from the procedure and remained stable through 12 months (capture threshold at 0.4 ms 0.8 ± 0.6 V, sense amplitude 4.5 ± 2.7 mV at 12 months). A total of five (14.3%) patients experienced seven complications, all of which were procedure-related. There were no device or procedure-related deaths. The total estimated battery longevity (accounting for time since implant) evaluated at 12 months was 11.3 ± 4.2 and 5.7 ± 2.6 years for the ventricular and atrial LPs, respectively. One patient required an atrial LP revision 10 months after implantation. The LP was retrieved and replaced. Conclusion: These data confirm the feasibility, safety, and long-term effectiveness of adding an atrial LP in patients with a pre-existing ventricular LP to achieve dual-chamber leadless pacing.

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.

Aims: In congenital long QT syndrome (cLQTS), monitoring of the heart rate–corrected QT interval (QTc) is essential as even transient prolongation can significantly increase the risk of torsades de pointes and sudden cardiac death. Apple Watch (AW) offers a single-lead mobile electrocardiogram (mECG), but its accuracy for QTc monitoring remains uncertain. The objective is to analytically validate AW mECGs for QTc measurement in paediatric and adult cLQTS patients, assessing agreement, systematic bias, and lead-specific feasibility compared with standard 12-lead ECG. Methods and results: In this cross-sectional, dual-centre study, patients with cLQTS underwent consecutive 12-lead ECG, followed by mECG recordings of Leads I and II. QT intervals were measured by two blinded investigators, and accuracy was evaluated using Bland–Altman analysis. The study was deemed exempt from formal ethical approval by the Medical Ethics Committee of the Amsterdam UMC. Of 101 patients enrolled, 99 had ECGs suitable for QTc analysis; 15 (15.2%) were younger than 18 years and 62 (62.6%) were female. On 12-lead ECG, the mean QTc was 444.9 ± 30.2 ms (Lead I) and 449.0 ± 29.8 ms (Lead II), compared with 466.6 ± 28.9 ms (Lead I) and 470.0 ± 29.8 ms (Lead II) on mECG. The mean QTc difference (12-lead—AW) was −21.7 ms (95% limits of agreement: −53.1–9.7) for Lead I and −21.0 ms (−59.5–17.5) for Lead II. Conclusion: In patients with cLQTS, AW-derived mECGs may complement, but not replace, standard 12-lead ECGs for QTc assessment, pending further validation in longitudinal and unsupervised settings.

BACKGROUND: MODULAR antitachycardia pacing (ATP), a multicenter, international trial, assesses a modular cardiac rhythm management system: a subcutaneous implantable cardioverter defibrillator in wireless communication with a leadless pacemaker (LP) capable of pace-terminating ventricular tachycardia. METHODS: Enrolees had one or more clinical risk factors for ventricular tachycardia and did not require chronic pacing. Complications included prespecified major LP system- and procedure-related complications, and any complication related to the LP, subcutaneous implantable cardioverter defibrillator, implantation, or study protocol. Survival analysis was performed to identify complication-free rates, therapy delivery, and all-cause mortality. RESULTS: The 297 patients enrolled had an ejection fraction of 35±13%, 43% secondary prevention indications, and 59% with prior ventricular arrhythmias. Of 286 patients undergoing LP implantation (100% success), 251 patients completed 12-month follow-up. Mortality rate was 6%, with none related to the implant procedure. Median follow-up duration was 23.4 months (interquartile range, 17.9–28.1). The LP major complication-free rate was 97.2%, exceeding the performance goal. The overall LP+ subcutaneous implantable cardioverter defibrillator system-related complication-free rate was 88.5%. Appropriate tachyarrhythmia-therapy (ATP+shock) rates were 14.4%, and appropriate shock rates were 8.5%. Inappropriate total tachyarrhythmia therapy was 9.5% of which 8.5% were shocks. ATP was 67.3% successful in terminating ventricular arrhythmia episodes and accelerated ventricular arrhythmias in 10.1% of episodes. Overall therapy burden (ATP+shock) was 96/100 patient-years, of which 44/100 patient-years was for shock delivery. CONCLUSIONS: One-year outcomes of the first modular pacing-defibrillator system reveal low system and LP complication rates and good ATP efficacy rates, suggesting that the modular cardiac rhythm management is a viable alternative to single-chamber implantable cardioverter defibrillators using low-energy pacing capability without the need for transvenous leads. CLINICAL TRIAL REGISTRATION: URL: https://clinicaltrials.gov/ ; Unique identifier: NCT04798768.

Aims: Subcutaneous implantable cardioverter-defibrillators (S-ICDs) are effective in patients who require protection from sudden cardiac death while avoiding the long-term risks associated with transvenous leads. However, data on their real-world performance in paediatric and young patients remain limited. This study aims to evaluate the safety and efficacy of S-ICDs in a large, multicentre cohort of paediatric and young patients across Europe, with a focus on contemporary implantation practices and clinical outcomes. Methods and results: This is an international, multicentre, observational, retrospective registry on S-ICD outcome in paediatric and young adult patients with congenital heart defects (CHD), cardiomyopathies, channelopathies, and idiopathic ventricular fibrillation (IVF). Data were collected on implantation techniques, acute and long-term outcomes, including defibrillation efficacy, inappropriate (IAS) and appropriate shocks, and complications. Follow-up data were analysed to assess device performance and safety. A total of 223 patients (mean age: 15 ± 3 years; 59% male, 53% cardiomyopathies, 18% channelopathies, 15% IVF, 14% CHD) were included. Most patients underwent implantation using an intermuscular (65%) and two-incision technique (88%). Acute defibrillation success was 100%, and no intraoperative complications occurred. The median follow-up was 28 (IQR: 12–55) months. Appropriate shocks were delivered in 41 (18%) patients (26% rate at 5 years). The first shock was effective in 92% of discrete episodes. The IAS and the complication rates were 20% and 5% at 5 years. Older age, intermuscular pocket, and two-incision technique were associated with fewer complications. Conclusion: This multicentre S-ICD European registry in paediatric and young patients demonstrated favourable outcomes, low IAS, and complication rates.