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.

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.

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.

Determinants of outcome impact of vein of Marshall ethanol infusion when added to catheter ablation of persistent atrial fibrillation: A secondary analysis of the VENUS randomized clinical trial.

BACKGROUND: The Vein of Marshall Ethanol for Untreated Persistent AF (VENUS) trial demonstrated that adding vein of Marshall (VOM) ethanol infusion to catheter ablation (CA) improves ablation outcomes in persistent atrial fibrillation (AF). There was significant heterogeneity in the impact of VOM ethanol infusion on rhythm control. OBJECTIVE: The purpose of this study was to assess the association between outcomes and (1) achievement of bidirectional perimitral conduction block and (2) procedural volume. METHODS: The VENUS trial randomized patients with persistent AF (N = 343) to CA combined with VOM ethanol or CA alone. The primary outcome (freedom from AF or atrial tachycardia [AT] lasting longer than 30 seconds after a single procedure) was analyzed by 2 categories: (1) successful vs no perimitral block and (2) high- (>20 patients enrolled) vs low-volume centers. RESULTS: In patients with perimitral block, the primary outcome was reached 54.3% after VOM-CA and 37% after CA alone (P = .01). Among patients without perimitral block, freedom from AF/AT was 34.0% after VOM-CA and 37.0% after CA (P = .583). In high-volume centers, the primary outcome was reached in 56.4% after VOM-CA and 40.2% after CA (P = .01). In low-volume centers, freedom from AF/AT was 30.77% after VOM-CA and 32.61% after CA (P = .84). In patients with successful perimitral block from high-volume centers, the primary outcome was reached in 59% after VOM-CA and 39.1% after CA (P = .01). Tests for interaction were significant (P = .002 for perimitral block and P = .04 for center volume). CONCLUSION: Adding VOM ethanol infusion to CA has a greater impact on outcomes when associated with perimitral block and performed in high-volume centers. Perimitral block should be part of the VOM procedure.

Effect of Catheter Ablation With Vein of Marshall Ethanol Infusion vs Catheter Ablation Alone on Persistent Atrial Fibrillation: The VENUS Randomized Clinical Trial.

Importance: Catheter ablation of persistent atrial fibrillation (AF) has limited success. Procedural strategies beyond pulmonary vein isolation have failed to consistently improve results. The vein of Marshall contains innervation and AF triggers that can be ablated by retrograde ethanol infusion. Objective: To determine whether vein of Marshall ethanol infusion could improve ablation results in persistent AF when added to catheter ablation. Design, Setting, and Participants: The Vein of Marshall Ethanol for Untreated Persistent AF (VENUS) trial was an investigator-initiated, National Institutes of Health-funded, randomized, single-blinded trial conducted in 12 centers in the United States. Patients (N = 350) with persistent AF referred for first ablation were enrolled from October 2013 through June 2018. Follow-up concluded in June 2019. Interventions: Patients were randomly assigned to catheter ablation alone (n = 158) or catheter ablation combined with vein of Marshall ethanol infusion (n = 185) in a 1:1.15 ratio to accommodate for 15% technical vein of Marshall ethanol infusion failures. Main Outcomes and Measures: The primary outcome was freedom from AF or atrial tachycardia for longer than 30 seconds after a single procedure, without antiarrhythmic drugs, at both 6 and 12 months. Outcome assessment was blinded to randomization treatment. There were 12 secondary outcomes, including AF burden, freedom from AF after multiple procedures, perimitral block, and others. Results: Of the 343 randomized patients (mean [SD] age, 66.5 [9.7] years; 261 men), 316 (92.1%) completed the trial. Vein of Marshall ethanol was successfully delivered in 155 of 185 patients. At 6 and 12 months, the proportion of patients with freedom from AF/atrial tachycardia after a single procedure was 49.2% (91/185) in the catheter ablation combined with vein of Marshall ethanol infusion group compared with 38% (60/158) in the catheter ablation alone group (difference, 11.2% [95% CI, 0.8%-21.7%]; P = .04). Of the 12 secondary outcomes, 9 were not significantly different, but AF burden (zero burden in 78.3% vs 67.9%; difference, 10.4% [95% CI, 2.9%-17.9%]; P = .01), freedom from AF after multiple procedures (65.2% vs 53.8%; difference, 11.4% [95% CI, 0.6%-22.2%]; P = .04), and success achieving perimitral block (80.6% vs 51.3%; difference, 29.3% [95% CI, 19.3%-39.3%]; P < .001) were significantly improved in vein of Marshall-treated patients. Adverse events were similar between groups. Conclusions and Relevance: Among patients with persistent AF, addition of vein of Marshall ethanol infusion to catheter ablation, compared with catheter ablation alone, increased the likelihood of remaining free of AF or atrial tachycardia at 6 and 12 months. Further research is needed to assess longer-term efficacy. Trial Registration: ClinicalTrials.gov Identifier: NCT01898221.

Targeted Left Ventricular Lead Implantation Strategy for Non-Left Bundle Branch Block Patients: The ENHANCE CRT Study.

OBJECTIVES: This study compared clinical outcomes between an increased electrical delay in the left ventricular region (QLV)-based LV lead implantation approach (QLV arm) and anatomical implantation approach (control arm) in patients with non-left bundle branch block. BACKGROUND: Limited data exist on cardiac resynchronization therapy effectiveness in patients with non-left bundle branch block. Clinicians generally deliver cardiac resynchronization therapy through an anatomical implantation approach; however, targeting the QLV may serve as an individualized implantation strategy in non-left bundle branch block patients. METHODS: The study enrolled 248 subjects at 29 U.S. centers. Subjects were randomized in a 2:1 ratio between a QLV-based implantation approach and anatomical implantation approach and were implanted with a St. Jude Medical quadripolar cardiac resynchronization therapy defibrillator system. The primary endpoint was the clinical composite score after 12 months of follow-up. RESULTS: The study analyzed 191 available subjects at 12 months of follow-up (128 QLV arm, 63 control arm). Of these, 39 subjects (26 in the QLV arm and 13 in the control arm) had heart failure events (8 cardiac deaths and 31 heart failure hospitalizations). Aside from New York Heart Association functional class, there were no other significant differences in baseline characteristics between the 2 arms. The responder rate at 12 months measured by the clinical composite score was 67.2% in the QLV arm and 73.0% in the control arm (p = 0.506). CONCLUSIONS: Although patient-tailored left ventricular lead placement guided by QLV is promising, we observed no difference in outcome between the QLV-based implantation approach and the conventional anatomical implantation approach.

Safety and feasibility of combined atrial fibrillation ablation and left atrial appendage occlusion after left atrial appendage electrical isolation.

OBJECTIVE: To demonstrate the feasibility of combining left atrial appendage electrical isolation (LAAEI) with left atrial appendage occlusion (LAAO) to increase efficacy of persistent/longstanding atrial fibrillation (PLAF) catheter ablation (CA) while mitigating risk of left atrial appendage (LAA) thrombus. BACKGROUND: CA for atrial fibrillation (AF) plus LAAO is safe and feasible. LAAEI may improve freedom from recurrence in PLAF but may increase LAA thrombus. METHODS: We performed 42 concomitant procedures in patients with PLAF. After standard lesions, LAAEI was performed. LAAO immediately followed ablation. If 3-month transesophageal echocardiogram (TEE) was benign, oral anticoagulation (OAC) was transitioned to dual antiplatelet therapy for 3 more months. RESULTS: Patients were 71.1 ± 8.5 years old, with CHADS2-VASc of 3.3 ± 1.1 and HAS-BLED of 2.5 ± 1.4. Twenty-eight of 42 patients (66.7%) were completely AF free over an average follow-up of 18.6 ± 8.6 months. The AF-free survival estimate was 94.5% at 1 year. There was no thromboembolism (TE) during the follow-up. There were six non-significant leaks acutely and six non-significant leaks at 6 months. There were three device-related thrombi, although 2/3 stopped OAC prematurely. CONCLUSION: A combined procedure is feasible and effective in treating arrhythmia and stroke risk associated with PLAF. The risk of TE despite OAC after LAAEI supports simultaneous LAAO.