The extravascular implantable cardioverter-defibrillator: characterization of anatomical parameters impacting substernal implantation and defibrillation efficacy.

AIMS: The aim of this study is to provide a thorough, quantified assessment of the substernal space as the site of extravascular implantable cardioverter-defibrillator (ICD) lead placement using computed tomography (CT) scans and summarizing adverse events and defibrillation efficacy across anatomical findings. Subcutaneous ICDs are an alternative to transvenous defibrillators but have limitations related to ICD lead distance from the heart. An alternative extravascular system with substernal lead placement has the potential to provide defibrillation at lower energy and pacing therapies from a single device. METHODS AND RESULTS: A multi-centre, non-randomized, retrospective analysis of 45 patient CT scans quantitatively and qualitatively assessing bony, cardiac, vascular, and other organ structures from two human clinical studies with substernal lead placement. Univariate logistic regression was used to evaluate 15 anatomical parameters for impact on defibrillation outcome and adjusted for multiple comparisons. Adverse events were summarized. Substernal implantation was attempted or completed in 45 patients. Defibrillation testing was successful in 37 of 41 subjects (90%) using ≥10 J safety margin. There were two intra-procedural adverse events in one patient, including reaction to anaesthesia and an episode of transient atrial fibrillation during ventricular fibrillation induction. Anatomical factors associated with defibrillation failure included large rib cage width, myocardium extending very posteriorly, and a low heart position in the chest (P-values <0.05), though not significant adjusting for multiple comparisons. CONCLUSION: Retrospective analysis demonstrates the ability to implant within the substernal space with low intra-procedural adverse events and high defibrillation efficacy despite a wide range of anatomical variability.

Retrospective Cohort Study Examining Reduced Intensity and Duration of Anticoagulant and Antiplatelet Therapy Following Left Atrial Appendage Occlusion with the WATCHMAN Device.

BACKGROUND: Anticoagulant and antiplatelet therapy are recommended following WATCHMAN implantation (45 days and 6 months) to reduce the risk of embolic events. These patients are often also at high risk of recurrent bleeding complications. We aimed to assess the safety of reduced duration of treatment with anticoagulant and antiplatelet therapy in the early post implant period. METHODS: This was a retrospective cohort study assessing the duration of antiplatelet and anticoagulant therapy in 47 consecutive patients following WATCHMAN implant. The primary outcome was rate of major bleeding, stroke and systemic embolic complications. The secondary endpoints were rate of device thrombus and peri-device leak >4mm as assessed by transoesophogeal echocardiography. RESULTS: Forty-seven patients were followed up for a mean of 2.4+/-1.7 years (111.4 total patient-years). The rate of stroke was 1.8/100 patient-years (two events) and the rate of major bleeding complication was 8.9/100 patient-years. Three patients had peri-device leak >4mm and no patients had device thrombus visualised. 70.2% of patients had discontinued anticoagulation at 45 days, 89.4% had discontinued dual antiplatelet therapy at 90 days. Seven patients were not on any form of anticoagulant or antiplatelet at five months. Comparison of probability of survival free from stroke by time of cessation of anticoagulant and antiplatelet therapy demonstrated no significant differences (p-value for log rank test 0.238 and 0.820). CONCLUSION: Following WATCHMAN implant shortened periods of anticoagulants and antiplatelets may be considered, particularly in the context of high bleeding risk.

Leadless Ultrasound-Based Cardiac Resynchronization System in Heart Failure.

Importance: Approximately 40% of patients with heart failure (HF) who are eligible for cardiac resynchronization therapy (CRT) either fail to respond or are untreatable due to anatomical constraints. Objective: To assess the safety and efficacy of a novel, leadless, left ventricular (LV) endocardial pacing system for patients at high risk for a CRT upgrade or whose coronary sinus (CS) lead placement/pacing with a conventional CRT system failed. Design, Setting, and Participants: The SOLVE-CRT study was a prospective multicenter trial enrolling January 2018 through July 2022, with follow-up at 6 months. Data were analyzed from January 17, 2018, through February 15, 2023. The trial combined data from an initial randomized, double-blind study (n = 108) and a subsequent single-arm part (n = 75). It took place at 36 centers across Australia, Europe, and the US. Participants were nonresponders, previously untreatable (PU), or high-risk upgrades (HRU). All participants contributed to the safety analysis. The primary efficacy analysis (n = 100) included 75 PU-HRU patients from the single-arm part and 25 PU-HRU patients from the randomized treatment arm. Interventions: Patients were implanted with the WiSE CRT System (EBR Systems) consisting of a leadless LV endocardial pacing electrode stimulated with ultrasound energy delivered by a subcutaneously implanted transmitter and battery. Main Outcomes and Measures: The primary safety end point was freedom from type I complications. The primary efficacy end point was a reduction in mean LV end systolic volume (LVESV). Results: The study included 183 participants; mean age was 68.1 (SD, 10.3) years and 141 were male (77%). The trial was terminated at an interim analysis for meeting prespecified stopping criteria. In the safety population, patients were either New York Heart Association Class II (34.6%) or III (65.4%). The primary efficacy end point was met with a 16.4% (95% CI, -21.0% to -11.7%) reduction in mean LVESV (P = .003). The primary safety end point was met with an 80.9% rate of freedom from type I complications (P < .001), which included 12 study device system events (6.6%), 5 vascular events (2.7%), 3 strokes (1.6%), and 7 cardiac perforations which mostly occurred early in the study (3.8%). Conclusions and Relevance: The SOLVE-CRT study has demonstrated that leadless LV endocardial pacing with the WiSE CRT system is associated with a reduction in LVESV in patients with HF. This novel system may represent an alternative to conventional CRT implants in some HF patient populations. Trial Registration: ClinicalTrials.gov Identifier: NCT0292203.

Ventricular tachycardia or supraventricular tachycardia?

It shows a pseudo -A-V-V-A response after stopping overdrive atrial pacing of a broad complex tachycardia.

Feasibility of leadless left ventricular septal pacing with the WiSE-CRT system to target the left bundle branch area: A porcine model and multicenter patient experience.

BACKGROUND: The WiSE-CRT system delivers leadless endocardial left ventricular (LV) pacing to achieve cardiac resynchronization therapy. The electrode is conventionally placed on the lateral wall, but implanting on the LV septum may have advantages, including capture of the left bundle branch, and improved battery longevity owing to reduced distance from the transmitter. OBJECTIVE: The purpose of this study was to assess the feasibility of leadless LV septal pacing via the WiSE-CRT system. METHODS: Two pigs underwent electrode implantation on the LV septum with subsequent anatomical and histological examination. Eight patients underwent implantation of the WiSE-CRT system with deployment of the electrode on the LV septum via an interatrial transseptal approach. RESULTS: Deployment of the electrode on the LV septum was successful in both animals. Histological examination demonstrated electrode tines in close proximity to Purkinje tissue. WiSE-CRT implantation with an LV septal electrode was successful in all patients. Biventricular capture was confirmed, with a significant reduction in QRS duration (187.1 ± 33.8 ms vs 149.5 ± 15.7 ms; P = .009). Temporary LV pacing achieved further QRS reduction (139.8 ± 12.4 ms), and in 4 patients the peak LV activation time in lead V5/V6 was <90 ms, suggesting left bundle branch capture. At early follow-up, the median LV pacing percentage was 98.5% and 5 patients (62.5%) improved symptomatically. The transmitter-to-electrode distance was lower than the distance to the lateral wall during acoustic window screening (8.8 ± 1.6 cm vs 11.9 ± 1.5 cm; P = .002). CONCLUSION: Leadless LV septal pacing with the WiSE-CRT system to target the left bundle branch appears feasible. Further study is required to assess the efficacy and safety of this technique.

Long-term longevity and clinical outcomes of Linox S/SD implantable cardioverter-defibrillator leads: a single-center experience.

PURPOSE: Since the introduction of the Biotronik Linox S/SD leads in 2006, there have been multiple reports of premature lead failure. The purpose of this study was to investigate the longevity of the Linox S/SD leads and to identify the possible predictors of lead failure in a single tertiary implant center. METHODS: We retrospectively reviewed patients who underwent implantation of Linox S/SD leads or Sorin Vigila 1CR/2CR leads (the same Linox S/SD leads marketed by Sorin) at our center. The cumulative lead survival was estimated using the Kaplan-Meier curve, and variables associated with lead failure were assessed by Cox proportional hazard model. RESULTS: A total of 187 patients (154 (82%) male) underwent Linox S/SD or Vigila 1CR/2CR implantation between 2007 and 2013. During follow-up with a median time of 75 months, nine lead failures were identified (4.8%). The mean and median times from lead implantation to lead failure were 70.7 ± 21 months and 64 (45-111) months, respectively. The cumulative survival probability for the Linox S/SD at 5 years was 97.1% and at 12 years was 90.3%. Non-physiological high-rate sensing was the most common type of lead failure in patients. In two-thirds of these patients, this led to inappropriate shock. We did not find any significant relationships between patients' clinical and procedural characteristics and lead failure. CONCLUSIONS: At our center, the 5-year lead survival of the Linox S/SD has been better than reports from other centers. The majority of lead failures presented as non-physiological high-rate sensing with subsequent inappropriate therapy.

Long-term performance of submammary defibrillator system.

AIMS: There are various implantation techniques that have been used to minimize the cosmetic effect of implantable cardioverter defibrillator (ICD) implantation, including submammary implantation. There are limited data on submammary ICD implantation and no data on long-term follow-up. We report the long-term performance of submammary ICD systems implanted in young females. METHODS AND RESULTS: We gathered data from August 1994 to September 2009 on all submammary ICD implantations undertaken at two institutes in Melbourne, Australia. Twenty submammary ICDs were implanted. Mean age at implantation was 21 +/- 10 years. Fifteen single chamber (VR) and five dual chamber (DR) systems were implanted. Twenty-five per cent were implanted for primary prophylaxis. Implantable cardioverter defibrillator implantation was predominantly for non-cardiomyopathy indications. Mean follow-up duration was 60 +/- 46 months. There were no deaths during follow-up. There were two early lead dislodgements and three late lead revisions. No extractions were performed. Five patients had appropriate and five patients had inappropriate ICD therapy. Mean duration to first appropriate therapy was 58 +/- 40 months. Stable sensing and high voltage (HV) lead performance were demonstrated (mean lowest effective defibrillation at implant vs. follow-up: 13 +/- 6 vs. 14 +/- 4 J, P = 0.8; R-wave amplitude: 9 +/- 3 vs. 8 +/- 2 mV, P = 0.6; HV lead impedance: 52 +/- 6 vs. 44 +/- 9 ohm, P = 0.1). A clinically insignificant rise in ventricular pacing threshold (0.6 +/- 0.2 V at implant vs. 1.6 +/- 0.6 V at follow-up, P < 0.001) and a decrease in pacing impedance (621 +/- 223 vs. 471 +/- 89 ohm, P = 0.02) were noted. CONCLUSION: Submammary ICD implantation in young females is feasible and safe. Long-term follow-up data reveal stable sensing and HV lead performance.

Junctional ectopic tachycardia (JET).

Junctional ectopic tachycardia (JET) is a tachyarrhythmia arising from the atrioventricular node and His bundle area. Enhanced normal automaticity has been postulated as the mechanism of JET in the majority of patients. It is more common in children and can be seen as congenital or in postoperative settings. It is often a narrow complex tachycardia but can present as a wide complex tachycardia as a result of aberrant conduction. Its differentiation from other arrhythmias especially atrioventricular nodal reentrant tachycardia (AVNRT) can be challenging. Medical treatment of JET is difficult, and catheter ablation remains the mainstay of treatment in refractory cases with a high risk of atrioventricular block and recurrence.

First-in-Human Chronic Implant Experience of the Substernal Extravascular Implantable Cardioverter-Defibrillator.

OBJECTIVES: The aim of this study was to evaluate the safety and performance of an extravascular (EV) implantable cardioverter-defibrillator (ICD). BACKGROUND: Limitations of existing transvenous and subcutaneous ICD systems include lead reliability and morbidity issues associated with ICD lead implantation in the vasculature or lack of pacing therapies (e.g., antitachycardia pacing) in subcutaneous systems. The EV defibrillator uses a novel substernal lead placement to address these limitations. METHODS: This was a prospective, nonrandomized, chronic pilot study conducted at 4 centers in Australia and New Zealand. Participants were 21 patients referred for ICD implantation. Patients received EV ICD systems. Data collection included major systemic and procedural adverse events, defibrillation testing at implantation, and sensing and pacing thresholds. RESULTS: Among 20 patients who underwent successful implantation, the median defibrillation threshold was 15 J, and 90% passed defibrillation testing with a ≥10-J safety margin. Mean R-wave amplitude was 3.4 ± 2.0 mV, mean ventricular fibrillation amplitude was 2.8 ± 1.7 mV, and pacing was successful in 95% at ≤10 V. There were no intraprocedural complications. Two patients have undergone elective chronic system removal since hospital discharge. In the 15 patients presently implanted, the systems are stable in long-term follow-up. CONCLUSIONS: This first-in-human evaluation of an EV ICD demonstrated the feasibility of substernal lead placement, defibrillation, and pacing with a chronically implanted system. There were no acute major complications, and pacing, defibrillation, and sensing performance at implantation were successful in most patients. (Extravascular ICD Pilot Study [EV ICD]; NCT03608670).

Left atrial appendage closure with WATCHMAN in Asian patients: 2 year outcomes from the WASP registry.

BACKGROUND: Left atrial appendage closure is a non-pharmacological alternative for stroke prevention in high-risk non-valvular atrial fibrillation patients, but has not been widely studied in Asian patients. The prospective WASP registry assessed real-world outcomes for patients undergoing WATCHMAN implant in the Asia-Pacific region. METHODS: Data were collected from consecutive patients across 9 centres. Major endpoints included procedural success, safety and long-term outcomes including occurrence of bleeding, stroke/transient ischaemic attack/systemic embolism and all-cause mortality. RESULTS: Subjects (n = 201) had a mean age of 70.8 ±â€¯9.4 years, high stroke risk (CHA2DS2-VASc: 3.9 ±â€¯1.7), elevated bleeding risk (HAS-BLED: 2.1 ±â€¯1.2) with 53% patients from Asian countries. Successful implantation occurred in 98.5% of patients; 7-day device/procedure-related SAE rate was 3.0%. After 2 years of follow-up, the rates of ischaemic stroke/TIA/SE and major bleeding were 1.9 and 2.2 per 100-PY, respectively, representing relative reductions of 77% and 49% versus expected rates per risk scores. The relative risk reductions versus expected rates were more pronounced in Asians vs. Non-Asians (89% vs 62%; 77% vs 14%). Other significant findings included larger mean LAA ostium diameter for Asians vs. Non-Asians (23.4 ±â€¯4.1 mm vs. 21.2 ±â€¯3.2 mm, p < 0.001) and hence requirement for larger median device size (27 mm for Asians, 24 mm for non-Asians [p < 0.0001]). CONCLUSION: Real-world experience of left atrial appendage closure with WATCHMAN has demonstrated low peri-procedural risk, and long-term efficacy for stroke and bleeding prevention in a primarily Asian cohort.

Chronic threshold testing of implantable cardioverter defibrillators does not increase coagulation activity or platelet activation.

It is unknown if the brief periods of circulatory statis occurring with induction of VF during DFT testing in patients with an ICD activate blood coagulation processes. To address this question, coagulation activity and platelet activation were measured in peripheral venous blood samples obtained from 12 patients undergoing DFT testing under general anesthesia, 3 (n = 11) or 6 months (n = 1) after ICD implantation for recurrent ventricular arrhythmias. Five patients were anticoagulated with warfarin and two to six episodes of VF (median five) were induced per patient. Blood samples were drawn at baseline, after each DFT test and on the following morning. Coagulation activity was assessed by measuring prothrombin fragment 1 + 2 (F1 + 2) (a marker of thrombin generation), soluble fibrin (a marker of fibrin production), and D-dimer (a breakdown product of cross-linked fibrin). Platelet activation was evaluated by measuring the expression P-selectin on the platelet surface using flow cytometry. No significant changes in F1 + 2, soluble fibrin, D-dimer, or P-selectin expression occurred during DFT testing, or between baseline and morning after samples. Moreover, results were unaffected by warfarin. These findings suggest that chronic threshold testing of implantable cardioverter defibrillators is not associated with activation of blood coagulation processes.