Atrioventricular Synchrony Delivered by a Dual-Chamber Leadless Pacemaker System.

BACKGROUND: A dual-chamber leadless pacemaker system has been designed for AV synchronous pacing using wireless, beat-to-beat, implant-to-implant (i2i) communication between distinct atrial and ventricular leadless pacemakers. The AV synchrony achieved across various ambulatory scenarios has yet to be systematically evaluated. METHODS: A prospective, single-arm, unblinded, multicenter, international clinical trial of the leadless pacemaker system was conducted in patients with a conventional dual-chamber pacing indication enrolled from February 2022 to March 2023. Leadless pacemaker systems were implanted, and 12-lead Holter electrocardiographic recordings were collected 3 months after implantation over various postures/activities: sitting, supine, left lateral recumbent, right lateral recumbent, standing, normal walk, and fast walk. An independent Holter core laboratory performed a manual adjudication of the percent of AV synchronous beats using the standard 300-millisecond PR interval limit. Atrium-to-ventricle and ventricle-to-atrium i2i communication success rates were also assessed. Post hoc summary statistics describing the relationships between AV synchrony and i2i success, posture/activity, implantation indication, AV event, and heart rate were calculated. RESULTS: In the evaluable population (n=384 of 464 enrolled [83%]; 61% male; age, 70 years; weight, 82 kg; 60% ejection fraction; 95% of beats evaluable), the mean AV synchrony of 98% of beats observed across all postures using the standard 300-millisecond limit was greater than both atrium-to-ventricle i2i (94%) and ventricle-to-atrium i2i (94%; P<0.001), exceeding both i2i values in 95% of patients. AV synchrony was achieved in >95% of evaluable beats across all postures/activities, implantation indications, AV paced/sensed event combinations, and heart rate ranges (including >100 bpm). CONCLUSIONS: This dual-chamber leadless pacemaker system demonstrated AV synchrony in 98% of evaluable beats at 3 months after implantation. AV synchrony was maintained across postures/activities and remained robust for heart rates >100 bpm.

Six-month electrical performance of the first dual-chamber leadless pacemaker.

BACKGROUND: The first dual-chamber leadless pacemaker (DC-LP) system consists of 2 separate atrial and ventricular devices that communicate to maintain synchronous atrioventricular pacing and sensing. The initial safety and efficacy were previously reported. OBJECTIVE: The purpose of this study was to evaluate the chronic electrical performance of the DC-LP system. METHODS: Patients meeting standard dual-chamber pacing indications were enrolled and implanted with the DC-LP system (Aveir DR, Abbott), including right atrial and ventricular helix-fixation LPs (atrial leadless pacemaker [ALP], ventricular leadless pacemaker [VLP]). Pacing capture threshold, sensed amplitude, and pacing impedance were collected using the device programmer at prespecified timepoints from 0-6 months postimplant. RESULTS: De novo devices were successfully implanted in 381 patients with complete 6-month data (62% male; age 69 ± 14 years; weight 82 ± 20 kg; 65% sinus nodal dysfunction, 30% atrioventricular block). ALPs were implanted predominantly in the right atrial appendage anterior base and VLPs primarily at the mid-to-apical right ventricular septum. From implant to 1 month, pacing capture thresholds (0.4-ms pulse width) improved in both ALPs (2.4 ± 1.5 V to 0.8 ± 0.8 V; P <.001) and VLPs (0.8 ± 0.6 V to 0.6 ± 0.4 V; P <.001). Sensed amplitudes improved in both ALPs (1.8 ± 1.3 mV to 3.4 ± 1.9 mV; P <.001) and VLPs (8.8 ± 4.0 mV to 11.7 ± 4.2 mV; P <.001). Impedances were stable in ALPs (334 ± 68 Ω to 329 ± 52 Ω; P = .17) and reduced in VLPs (789 ± 351 Ω to 646 ± 190 Ω; P <.001). Electrical measurements remained relatively stable from 1-6 months postimplant. No differences in electrical metrics were observed among ALP or VLP implant locations. CONCLUSION: This first in-human evaluation of the new dual-chamber leadless pacemaker system demonstrated reliable electrical performance throughout the initial 6-month evaluation period.

A Modular Communicative Leadless Pacing-Defibrillator System.

BACKGROUND: The subcutaneous implantable cardioverter-defibrillator (ICD) is associated with fewer lead-related complications than a transvenous ICD; however, the subcutaneous ICD cannot provide bradycardia and antitachycardia pacing. Whether a modular pacing-defibrillator system comprising a leadless pacemaker in wireless communication with a subcutaneous ICD to provide antitachycardia and bradycardia pacing is safe remains unknown. METHODS: We conducted a multinational, single-group study that enrolled patients at risk for sudden death from ventricular arrhythmias and followed them for 6 months after implantation of a modular pacemaker-defibrillator system. The safety end point was freedom from leadless pacemaker-related major complications, evaluated against a performance goal of 86%. The two primary performance end points were successful communication between the pacemaker and the ICD (performance goal, 88%) and a pacing threshold of up to 2.0 V at a 0.4-msec pulse width (performance goal, 80%). RESULTS: We enrolled 293 patients, 162 of whom were in the 6-month end-point cohort and 151 of whom completed the 6-month follow-up period. The mean age of the patients was 60 years, 16.7% were women, and the mean (±SD) left ventricular ejection fraction was 33.1±12.6%. The percentage of patients who were free from leadless pacemaker-related major complications was 97.5%, which exceeded the prespecified performance goal. Wireless-device communication was successful in 98.8% of communication tests, which exceeded the prespecified goal. Of 151 patients, 147 (97.4%) had pacing thresholds of 2.0 V or less, which exceeded the prespecified goal. The percentage of episodes of arrhythmia that were successfully terminated by antitachycardia pacing was 61.3%, and there were no episodes for which antitachycardia pacing was not delivered owing to communication failure. Of 162 patients, 8 died (4.9%); none of the deaths were deemed to be related to arrhythmias or the implantation procedure. CONCLUSIONS: The leadless pacemaker in wireless communication with a subcutaneous ICD exceeded performance goals for freedom from major complications related to the leadless pacemaker, for communication between the leadless pacemaker and subcutaneous ICD, and for the percentage of patients with a pacing threshold up to 2.0 V at a 0.4-msec pulse width at 6 months. (Funded by Boston Scientific; MODULAR ATP ClinicalTrials.gov NCT04798768.).

Revolutionizing Atrial Fibrillation Treatment: The Robotic Convergent Plus Procedure.

Atrial fibrillation (AF) is widely accepted to be the most common sustained arrhythmia, with an increasing incidence over time. This is thought to be due to the aging population across the world. AF occurs when abnormal electrical foci result in disorganization of atrial depolarization, though the exact pathophysiology leading to these abnormal foci is not well understood. A range of interventions exist for AF - pharmacological therapies (anti-arrhythmic or negative chronotropic medications), cardioversion, or ablations to interrupt the abnormal conduction pathways. Ablation may be via a catheter-based approach, via a surgical approach using the "Maze" procedure (Cox-Maze IV), or more recently, via a hybrid approach. This first involves a surgical epicardial ablation, with catheter-based endocardial ablation following a few weeks later to ensure durable transmural lesion sets via the "Convergent" procedure. We describe the use of the Da Vinci Xi™ robotic platform to improve the procedure, allowing continuous and improved visualization of the anatomy without the need for potentially harmful retraction of the atrial appendage or the back of the left atrium, as well as increased precision with our mapping tools and more complete ablation. Here, we highlight the advantages over a non-robotic (subxiphoid) Convergent procedure, while outlining the key operative steps in undertaking the "Robotic Convergent Plus" procedure using the Da Vinci Xi™ robotic surgical system.

Retrieval of Chronically Implanted Dual-chamber Leadless Pacemakers in an Ovine Model.

BACKGROUND: The clinical utilization of leadless pacemakers (LPs) as an alternative to traditional transvenous pacemakers is likely to increase with the advent of dual-chamber LP systems. Since device retrieval to allow LP upgrade or replacement will become an important capability, the first such dual-chamber, helix-fixation LP system (Aveir DR; Abbott, Abbott Park, IL) was specifically designed to allow catheter-based retrieval. In this study, the preclinical performance and safety of retrieving chronically implanted dual-chamber LPs was evaluated. METHODS: Atrial and ventricular LPs were implanted in the right atrial appendage and right ventricular apex of 9 healthy ovine subjects. After ≈2 years, the LPs were retrieved using a dedicated transvenous retrieval catheter (Aveir Retrieval Catheter; Abbott) by snaring, docking, and unscrewing from the myocardium. Comprehensive necropsy/histopathology studies were conducted to evaluate device- and procedure-related outcomes. RESULTS: At a median of 1.9 years postimplant (range, 1.8-2.6), all 18 of 18 (100%) LPs were retrieved from 9 ovine subjects without complications. The median retrieval procedure duration for both LPs, from first-catheter-in to last-catheter-out, was 13.3 minutes (range, 2.5-36.4). Postretrieval, all right atrial, and right ventricular implant sites demonstrated minimal tissue disruption, with intact fibrous tissue limited to the distal device body. No significant device-related trauma, perforation, pericardial effusion, right heart or tricuspid valve injury, or chronic pulmonary thromboembolism were observed at necropsy. CONCLUSIONS: This preclinical study demonstrated the safe and effective retrieval of chronically implanted, helix-fixation, dual-chamber LP systems, paving the way for clinical studies of LP retrieval.

Design and rationale of the MODULAR ATP global clinical trial: A novel intercommunicative leadless pacing system and the subcutaneous implantable cardioverter-defibrillator.

Background: The subcutaneous implantable cardioverter-defibrillator (S-ICD) has demonstrated safety and efficacy for the treatment of malignant ventricular arrhythmias. However, a limitation of the S-ICD lies in the inability to either pace-terminate ventricular tachycardia or provide prolonged bradycardia pacing support. Objective: The rationale and design of a prospective, single-arm, multinational trial of an intercommunicative leadless pacing system integrated with the S-ICD will be presented. Methods: A technical description of the modular cardiac rhythm management (mCRM) system (EMPOWER leadless pacemaker and EMBLEM S-ICD) and the implantation procedure is provided. MODULAR ATP (Effectiveness of the EMPOWER™ Modular Pacing System and EMBLEM™ Subcutaneous ICD to Communicate Antitachycardia Pacing) is a multicenter, international trial enrolling up to 300 patients at risk of sudden cardiac death at up to 60 centers trial design. The safety endpoint of freedom from major complications related to the mCRM system or implantation procedure at 6 months and 2 years are significantly higher than 86% and 81%, respectively, and all-cause survival is significantly >85% at 2 years. Results: Efficacy endpoints are that at 6 months mCRM communication success is significantly higher than 88% and the percentage of subjects with low and stable thresholds is significantly higher than 80%. Substudies to evaluate rate-responsive features and performance of the pacing module are also described. Conclusion: The MODULAR ATP global clinical trial will prospectively test the safety and efficacy of the first intercommunicating leadless pacing system with the S-ICD. This trial will allow for robust validation of device-device communication, pacing performance, rate responsiveness, and system safety.

A Dual-Chamber Leadless Pacemaker.

BACKGROUND: Single-chamber ventricular leadless pacemakers do not support atrial pacing or consistent atrioventricular synchrony. A dual-chamber leadless pacemaker system consisting of two devices implanted percutaneously, one in the right atrium and one in the right ventricle, would make leadless pacemaker therapy a treatment option for a wider range of indications. METHODS: We conducted a prospective, multicenter, single-group study to evaluate the safety and performance of a dual-chamber leadless pacemaker system. Patients with a conventional indication for dual-chamber pacing were eligible for participation. The primary safety end point was freedom from complications (i.e., device- or procedure-related serious adverse events) at 90 days. The first primary performance end point was a combination of adequate atrial capture threshold and sensing amplitude at 3 months. The second primary performance end point was at least 70% atrioventricular synchrony at 3 months while the patient was sitting. RESULTS: Among the 300 patients enrolled, 190 (63.3%) had sinus-node dysfunction and 100 (33.3%) had atrioventricular block as the primary pacing indication. The implantation procedure was successful (i.e., two functioning leadless pacemakers were implanted and had established implant-to-implant communication) in 295 patients (98.3%). A total of 35 device- or procedure-related serious adverse events occurred in 29 patients. The primary safety end point was met in 271 patients (90.3%; 95% confidence interval [CI], 87.0 to 93.7), which exceeded the performance goal of 78% (P<0.001). The first primary performance end point was met in 90.2% of the patients (95% CI, 86.8 to 93.6), which exceeded the performance goal of 82.5% (P<0.001). The mean (±SD) atrial capture threshold was 0.82±0.70 V, and the mean P-wave amplitude was 3.58±1.88 mV. Of the 21 patients (7%) with a P-wave amplitude of less than 1.0 mV, none required device revision for inadequate sensing. At least 70% atrioventricular synchrony was achieved in 97.3% of the patients (95% CI, 95.4 to 99.3), which exceeded the performance goal of 83% (P<0.001). CONCLUSIONS: The dual-chamber leadless pacemaker system met the primary safety end point and provided atrial pacing and reliable atrioventricular synchrony for 3 months after implantation. (Funded by Abbott Medical; Aveir DR i2i ClinicalTrials.gov number, NCT05252702.).

Dual-chamber leadless pacing: Atrioventricular synchrony in preclinical models of normal or blocked atrioventricular conduction.

BACKGROUND: Dual-chamber leadless pacemakers (LPs) require robust communication between distinct right atrial (RA) and right ventricular (RV) LPs to achieve atrioventricular (AV) synchrony. OBJECTIVE: The purpose of this preclinical study was to evaluate a novel, continuous implant-to-implant (i2i™) communication methodology for maintaining AV-synchronous, dual-chamber DDD(R) pacing by the 2 LPs. METHODS: RA and RV LPs were implanted and paired in 7 ovine subjects (4 with induced complete heart block). AV synchrony (% AV intervals <300 ms) and i2i communication success (% successful i2i transmissions between LPs) were evaluated acutely and chronically. During acute testing, 12-lead electrocardiographic and LP diagnostic data were collected from 5-minute recordings, in 4 postures and 2 rhythms (AP-VP and AS-VP, or AP-VS and AS-VS) per subject. Chronic i2i performance was evaluated through 23 weeks postimplant (final i2i evaluation period: week 16-23). RESULTS: Acute AV synchrony and i2i communication success across multiple postures and rhythms were median [interquartile range] 100.0% [100.0%-100.0%] and 99.9% [99.9%-99.9%], respectively. AV synchrony and i2i success rates did not differ across postures (P = .59, P = .11) or rhythms (P = 1, P = .82). During the final i2i evaluation period, the overall i2i success was 98.9% [98.1%-99.0%]. CONCLUSION: Successful AV-synchronous, dual-chamber DDD(R) leadless pacing using a novel, continuous, wireless communication modality was demonstrated across variations in posture and rhythm in a preclinical model.

Defibrillation effectiveness and safety of the shock waveform used in a contemporary wearable cardioverter defibrillator: Results from animal and human studies.

INTRODUCTION: The wearable cardioverter defibrillator (WCD) is used to protect patients at risk for sudden cardiac arrest. We examined defibrillation efficacy and safety of a biphasic truncated exponential waveform designed for use in a contemporary WCD in three animal studies and a human study. METHODS: Animal (swine) studies: #1: Efficacy comparison of a 170J BTE waveform (SHOCK A) to a 150J BTE waveform (SHOCK B) that approximates another commercially available waveform. Primary endpoint first shock success rate. #2: Efficacy comparison of the two waveforms at attenuated charge voltages in swine at three prespecified impedances. Primary endpoint first shock success rate. #3: Safety comparison of SHOCK A and SHOCK B in swine. Primary endpoint cardiac biomarker level changes baseline to 6 and 24 hours post-shock. Human Study: Efficacy comparison of SHOCK A to prespecified goal and safety evaluation. Primary endpoint cumulative first and second shock success rate. Safety endpoint adverse events. RESULTS: Animal Studies #1: 120 VF episodes in six swine. First shock success rates for SHOCK A and SHOCK B were 100%; SHOCK A non-inferior to SHOCK B (entire 95% CI of rate difference above -10% margin, p < .001). #2: 2,160 VF episodes in thirty-six swine. Attenuated SHOCK A was non-inferior to attenuated SHOCK B at each impedance (entire 95% CI of rate difference above -10% margin, p < .001). #3: Ten swine, five shocked five times each with SHOCK A, five shocked five times each with SHOCK B. No significant difference in troponin I (p = 0.658) or creatine phosphokinase (p = 0.855) changes from baseline between SHOCK A and SHOCK B. Human Study: Thirteen patients, 100% VF conversion rate. Mild skin irritation from adhesive defibrillation pads in three patients. CONCLUSIONS: The BTE waveform effectively and safely terminated induced VF in swine and a small sample in humans. TRIAL REGISTRATION: Human study clinical trial registration: URL: https://clinicaltrials.gov; Unique identifier: NCT04132466.

Same-day discharge following catheter ablation and venous closure with VASCADE MVP: A postmarket registry.

INTRODUCTION: Early and safe ambulation can facilitate same-day discharge (SDD) following catheter ablation, which can reduce resource utilization and healthcare costs and improve patient satisfaction. This study evaluated procedure success and safety of the VASCADE MVP venous vascular closure system in patients with atrial fibrillation (AF). METHODS: The AMBULATE SDD Registry is a two-stage series of postmarket studies in patients with paroxysmal or persistent AF undergoing catheter ablation followed by femoral venous access-site closure with VASCADE MVP. Efficacy endpoints included SDD success, defined as the proportion of patients discharged the same day who did not require next-day hospital intervention for procedure/access site-related complications, and access site sustained success within 15 days of the procedure. RESULTS: Overall, 354 patients were included in the pooled study population, 151 (42.7%) treated for paroxysmal AF and 203 (57.3%) for persistent AF. SDD was achieved in 323 patients (91.2%) and, of these, 320 (99.1%) did not require subsequent hospital intervention based on all study performance outcomes. Nearly all patients (350 of 354; 98.9%) achieved total study success, with no subsequent hospital intervention required. No major access-site complications were recorded. Patients who had SDD were more likely to report procedure satisfaction than patients who stayed overnight. CONCLUSION: In this study, 99.7% of patients achieving SDD required no additional hospital intervention for access site-related complications during follow-up. SDD appears feasible and safe for eligible patients after catheter ablation for paroxysmal or persistent AF in which the VASCADE MVP is used for venous access-site closure.

Design of the remede System Therapy (reST) study: A prospective non-randomized post-market study collecting clinical data on safety and effectiveness of the remede system for the treatment of central sleep apnea.

BACKGROUND: Central sleep apnea (CSA) is a disorder defined by lack of respiratory drive from the brain stem on breathing efforts. There is a lack of established therapies for CSA and most available therapies are limited by poor patient adherence, limited randomized controlled studies, and potentially adverse cardiovascular effects. The remede System (ZOLL Respicardia, Inc., Minnetonka, Minnesota) uses transvenous phrenic nerve stimulation to stimulate the diaphragm, thereby restoring a more normal breathing pattern throughout the sleep period. METHODS: The remede System Therapy (reST) Study is a prospective non-randomized multicenter international study evaluating long-term safety and effectiveness of the remede System in the post-market setting. Up to 500 adult patients with moderate to severe CSA will be enrolled and followed up to 5 years at approximately 50 sites in the United States and Europe. Safety objectives include evaluation of adverse events related to the implant procedure, device or delivered therapy, death, and hospitalizations. Effectiveness endpoints include assessment of changes in sleep-disordered breathing metrics from polysomnograms and home sleep tests, changes in daytime sleepiness using the Epworth Sleepiness Scale, and changes in QoL using the PROMIS-29 and Patient Global Assessment questionnaires. The subgroup of patients with heart failure will undergo additional assessments including echocardiography to assess cardiac reverse remodeling, 6-min walk distance, QoL assessment by Kansas City Cardiomyopathy Questionnaire and measurement of biomarkers. CONCLUSION: This will be the largest prospective study evaluating long-term safety and effectiveness of transvenous phrenic nerve stimulation for the treatment of moderate to severe CSA in adult patients.

Wireless Communication Between Paired Leadless Pacemakers for Dual-Chamber Synchrony.

BACKGROUND: Leadless pacemakers (LPs) can mitigate conventional pacemaker complications related to the transvenous leads and subcutaneous pocket surrounding the pulse generator. Although single-chamber leadless pacing has been established, multichamber pacing requires wireless bidirectional communication across multiple LPs to maintain synchrony. This preclinical study demonstrates the chronic performance of implant-to-implant (i2i) communication that achieves synchronous, dual-chamber pacing with 2 LPs. METHODS: The i2i communication modality employs subthreshold electrical signals conducted between implanted LPs through the blood and myocardial tissue on a beat-by-beat basis. Right atrial and right ventricular LPs were implanted in 9 ovine subjects. The i2i transmission performance was evaluated 13 weeks after implant. RESULTS: Right atrial and right ventricular LPs were implanted successfully and without complication in 9 ovine subjects. A total of 8715±457 right atrial-to-right ventricular and right ventricular-to-right atrial transmissions were sent per hour, with a success rate of 99.2±0.9%. Of periods with i2i communication failure when DDD pacing was not possible, 97.3±1.8% were resolved within 6 s. CONCLUSIONS: For the first time, synchronized, dual-chamber pacing has been demonstrated in a chronic preclinical feasibility study by 2 leadless pacemakers using beat-to-beat, wireless communication, achieving a success rate of 99.2%.

Comparison of anticoagulation with left atrial appendage closure after atrial fibrillation ablation: Rationale and design of the OPTION randomized trial.

BACKGROUND: For patients with symptomatic atrial fibrillation (AF), physicians typically offer AF ablation for symptom relief; however, patients often anticipate/expect a life free from anticoagulation. This belief puts patients at increased risk of stroke due to the potential for asymptomatic AF postablation if anticoagulation is ceased contrary to clinical guidelines. Although the WATCHMAN device has been FDA-approved to decrease the risk of thromboembolism from the left atrial appendage (LAA) in patients with an appropriate rationale to avoid oral anticoagulation, it has not been well-studied following AF ablation. Additionally, there are limited data comparing the WATCHMAN device to direct oral anticoagulants. The OPTION study will investigate whether LAA closure with the WATCHMAN FLX device is a reasonable alternative to oral anticoagulation following percutaneous catheter ablation for nonvalvular AF. TRIAL DESIGN: OPTION is a multinational, multicenter, prospective randomized clinical trial. Patients with a CHA2DS2-VASc of ≥2 in men or ≥3 in women and who underwent a AF catheter ablation procedure between 90 and 180 days prior to randomization (sequential) or are planning to have catheter ablation within 10 days of randomization (concomitant) will be randomized in a 1:1 allocation of WATCHMAN FLX vs control. Control patients will start or continue market-approved oral anticoagulation for the duration of the trial. A total of 1600 patients were randomized from 130 global investigational sites. Follow-up for both device and control patients will occur at 3, 12, 24, and 36 months. The primary effectiveness noninferiority endpoint is stroke (ischemic or hemorrhagic), all-cause death, or systemic embolism at 36 months. The primary safety superiority endpoint is nonprocedural bleeding through 36 months (International Society on Thrombosis and Haemostasis [ISTH] major bleeding or clinically relevant nonmajor bleeding). The secondary noninferiority endpoint is ISTH major bleeding through 36 months (including procedural bleeding). CONCLUSIONS: This trial will assess the safety and efficacy of WATCHMAN FLX in a postablation contemporary clinical AF patient population at risk of stroke.

A wearable cardioverter defibrillator with a low false alarm rate.

INTRODUCTION: A wearable cardioverter defibrillator (WCD) is indicated in appropriate patients to reduce the risk for sudden cardiac death. Challenges for patients wearing a WCD have been frequent false shock alarms primarily due to electrocardiogram noise and wear discomfort. The objective of this study was to test a contemporary WCD designed for reduced false shock alarms and improved comfort. METHODS: One hundred and thirty patients with left ventricular ejection fraction ≤40% and an active implantable cardioverter defibrillator (ICD) were fitted with the ASSURE WCD (Kestra Medical Technologies) and followed for 30 days. WCD detection was enabled and shock alarm markers recorded, but shocks and shock alarms were disabled. All WCD episodes and ICD ventricular tachycardia/ventricular fibrillation (VT/VF) episodes were adjudicated. The primary endpoint was the false-positive shock alarm rate with a performance goal of 1 every 3.4 days (0.29 per patient-day). RESULTS: Of 163 WCD episodes, 4 were VT/VF and 159 non-VT/VF (121 rhythms with noise, 32 uncertain with noise, 6 atrial flutter without noise). Only three false-positive shock alarm markers were recorded; one false-positive shock alarm every 1333 patient-days (0.00075 per patient-day, 95% confidence interval: 0.00015-0.00361; p < .001). No ICD recorded VT/VF episodes meeting WCD detection criteria (≥170 bpm for ≥20 s) were missed by the WCD during 3501 patient-days of use. Median wear was 31.0 days (interquartile range [IQR] 2.0) and median daily use 23.0 h (IQR 1.7). Adverse events were mostly mild: skin irritation (19.4%) and musculoskeletal discomfort (8.5%). CONCLUSION: The ASSURE WCD demonstrated a low false-positive shock alarm rate, low patient-reported discomfort, and no serious adverse events.