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Structured AbstractObjectivesThis study assessed safety and feasibility of a novel extravascular (EV) implantable cardioverter-defibrillator (ICD) lead when inserted anteriorly through a rib space and connected to various commercially available ICD pulse generators (PGs) placed in either a left mid-axillary or left pectoral pocket.BackgroundCurrently available or investigational, EV-ICDs include a subcutaneous or subxiphoid lead connected to customized EV-ICD PGs. This novel EV-ICD (AtaCor Medical, Inc, San Clemente, CA) employs a unique intercostal implant technique and is designed to function with commercial DF-4 ICD PGs.MethodsIn this non-randomized, single-center, acute study, 36 de novo or replacement transvenous (TV) ICD patients enrolled to receive a concomitant EV-ICD lead inserted through an intercostal space along the left parasternal margin. EV-ICD leads were connected to DF-4 compatible ICD PGs positioned in either a left mid-axillary or pectoral pocket for acute sensing and defibrillation testing. Defibrillation testing started at 30 Joules (J) and stepped down in 10 J increments following conversion success and stepped up in 5 J increments following conversion failure.ResultsSuccessful acute defibrillation using ≤ 35 J was noted in 100% of left mid-axillary PG subjects (n=27, mean 16.3 ± 8.6 J) and 83% of left pectoral PG subjects (n=6, mean 21.0 ± 8.4 J). All evaluable episodes (n=93) were automatically sensed, detected, and shocked. No serious device-related intraoperative adverse events were observed.ConclusionsThis first-in-human study documented safe and reliable placement of a novel extravascular ICD lead with effective sensing and defibrillation of induced ventricular fibrillation using commercial DF-4 ICD pulse generators.Condensed AbstractThis study assessed feasibility of intercostal implantation of a novel extravascular implantable cardioverter-defibrillator (ICD) lead designed to function with commercial DF-4 pulse generators (PGs). Lead placement was successful in 33 of 36 attempts (94%). Acute defibrillation with ≤35 J was successful in 27 of 27 left mid-axillary PG subjects (100%) and 5 of 6 left pectoral PG subjects (83%). All evaluable episodes (n=93) were automatically detected. No serious device-related intraoperative adverse events were observed. This study demonstrates feasibility of a novel extravascular ICD lead with effective sensing and defibrillating of induced ventricular fibrillation using commercial DF-4 PGs.

Background The subcutaneous implantable cardioverter-defibrillator (S-ICD) is developed to overcome lead-related complications and systemic infections, inherent to transvenous ICD (TV-ICD) therapy. The PRAETORIAN trial demonstrated that the S-ICD is non-inferior to the TV-ICD with regard to the combined primary endpoint of inappropriate shocks and complications. This prespecified secondary analysis evaluates all complications in the PRAETORIAN trial. Methods and results The PRAETORIAN trial is an international, multicentre, randomized trial in which 849 patients with an indication for ICD therapy were randomized to receive an S- ICD (N = 426) or TV-ICD (N = 423) and followed for a median of 49 months. Endpoints were device-related complications, lead-related complications, systemic infections, and the need for invasive interventions. Thirty-six device-related complications occurred in 31 patients in the S-ICD group of which bleedings were the most frequent. In the TV-ICD group, 49 complications occurred in 44 patients of which lead dysfunction was most frequent (HR: 0.69; P = 0.11). In both groups, half of all complications were within 30 days after implantation. Lead-related complications and systemic infections occurred significantly less in the S-ICD group compared with the TV-ICD group (P < 0.001, P = 0.03, respectively). Significantly more complications required invasive interventions in the TV-ICD group compared with the S-ICD group (8.3% vs. 4.3%, HR: 0.59; P = 0.047). Conclusion This secondary analysis shows that lead-related complications and systemic infections are more prevalent in the TV-ICD group compared with the S-ICD group. In addition, complications in the TV-ICD group were more severe as they required significantly more invasive interventions. This data contributes to shared decision-making in clinical practice.

Early subcutaneous implantable cardioverter-defibrillator (S-ICD) studies included atypical cohorts of patients who were younger with fewer comorbidities. Recent S-ICD studies included patient populations with more comorbidities.The goals of this study were to determine the incidence and predictors of S-ICD-related infection over a 3-year follow-up period and to use these results to develop an infection risk score.The S-ICD Post Approval Study is a US prospective registry of 1637 patients. Baseline demographic characteristics and outcomes with 3-year postimplantation follow-up were compared between patients with and without device-related infection. A risk score was derived from multivariable proportional hazards analysis of 22 variables.Infection was observed in 55 patients (3.3%), with 69% of infections occurring within 90 days and a vast majority (92.7%) within 1 year of implantation. Late infections more likely involved device erosion; no infections occurred after year 2. The annual mortality rate postinfection was 0.6%/y. No lead extraction complications or bacteremia related to infection were observed. An infection risk score was created with diabetes, age, prior transvenous ICD implant, and ejection fraction as predictors. Patients with a risk score of ≥3 had an 8.8 hazard ratio (95% confidence interval 2.8-16.3) of infection compared with a 0 risk score.Infection rates in the S-ICD Post Approval Study were similar to other S-ICD populations and not associated with systemic blood-borne infections. Late infection (1 year) is uncommon and associated with system erosion. A high-risk infection cohort can be identified that may facilitate preventive measures.

Objectives This study evaluated spontaneous arrhythmias and clinical outcomes in the S-ICD System PAS (Subcutaneous Implantable Cardioverter-Defibrillator Post Approval Study) cohort. Background The U.S. S-ICD PAS trial patient population more closely resembles transvenous ICD cohorts than earlier studies, which included many patients with little structural heart disease and few comorbidities. Early outcomes and low peri-operative complication rates were demonstrated in the S-ICD PAS cohort, but there are no data detailing spontaneous arrhythmias and clinical outcomes. Methods The S-ICD PAS prospective registry included 1,637 de novo patients from 86 U.S. centers. Descriptive statistics, Kaplan-Meier time to event, and multivariate logistic regression were performed using data out to 365 days. Results Patients (68.5% men; mean ejection fraction of 32.0%; 42.9% ischemic; 13.4% on dialysis) underwent implantation for primary (76.6%) or secondary prevention indication. The complication-free rate was 92.2%. The appropriate shock (AS) rate was 5.3%. A total of 395 ventricular tachycardia (VT) or fibrillation (VF) episodes were appropriately sensed, with 131 (33.2%) self-terminating. First and final shock efficacy (up to 5 shocks) for the 127 discrete AS episodes were 91.3% and 100.0%, respectively. Discrete AS episodes included 67 monomorphic VT (MVT) and 60 polymorphic VT (PVT)/VF, with first shock efficacy of 95.5% and 86.7%, respectively. There were 19 storm events in 18 subjects, with 84.2% conversion success. Storm episodes were more likely PVT/VF (98 of 137). Conclusions In the first year after implantation, a predominantly primary prevention population with low ejection fraction demonstrated a high complication-free rate and spontaneous event shock efficacy for MVT and PVT/VF arrhythmias at rapid ventricular rates. (Subcutaneous Implantable Cardioverter-Defibrillator System Post Approval Study [S-ICD PAS; NCT01736618)

Background: Suboptimal positioning of the subcutaneous implantable cardioverter-defibrillator (S-ICD) increases the defibrillation threshold and risk of conversion failure. Objective: Our objective is to develop a tool to evaluate the implant position and predict defibrillation success of the S-ICD: the PRAETORIAN score. Methods: The PRAETORIAN score is based on clinical and computer modeling knowledge of determinants affecting the defibrillation threshold: subcoil fat, subgenerator fat, and anterior positioning of the S-ICD generator. The score evaluates these determinants on the postoperative anterior-posterior and lateral chest radiographs and has 3 categories: 30–

BACKGROUND Traditionally, implantation of the subcutaneous implantable cardioverter defibrillator (S-ICD) requires incisions near the lateral chest wall, the xyphoid, and the superior sternal region (three-incision technique [3IT]). A two-incision technique (2IT) avoids the superior incision and has been shown to be a viable alternative in small studies with limited follow-up. OBJECTIVES To report on the long-term safety and efficacy of the 2IT compared to the 3IT procedure in a large patient cohort. METHODS Patients enrolled in the S-ICD post approval study (PAS) were stratified by procedural technique (2IT vs. 3IT). Baseline demographics, comorbidities and procedural outcomes were collected. Complications and S-ICD effectiveness in treating ventricular arrhythmias through an average 3-year follow-up period were compared. RESULTS Of 1637 patients enrolled in the S-ICD PAS, 854 pts (52.2%) were implanted using the 2IT and 782 were implanted using the 3IT (47.8%). The 2IT became more prevalent over time, increasing from 40% to 69% of implants (Q1-Q4). Mean procedure time was shorter with 2IT (69.0 vs. 86.3 min, p

Background A novel modular cardiac rhythm management (mCRM) therapy approach is evaluated in this study: the performance of an anti-tachycardia pacing enabled leadless pacemaker (LP) commanded by a subcutaneous-ICD (S-ICD) via wireless, intra-body, device-device communication (DDC). Objectives To investigate long-term DDC performance of linked S-ICD to LP (mCRM System) and factors that impact DDC performance. Methods The mCRM System was implanted in 37 canine subjects: 33 with an S-ICD and an LP; 4 with an S-ICD and 2 LPs. The S-ICD was implanted using a Parsonnet pouch in the first 8 subjects. Communication thresholds were measured in three postures up to 18 months. Percent tissue encapsulation of the LP was measured at necropsy and ranged from 6% to 100% (mean: 62%). S-ICD system migration was evaluated radiographically at implant vs. at necropsy in two planes (anterior-posterior and left lateral) and evaluated 0–3 scale: none, minimal, moderate, significant. Communication thresholds were evaluated at 0 vs. 3 days using a t-test and 3 days through 18 months using a linear regression analysis. A repeated measures generalized linear model (GLM) was used to evaluate if test posture, percent tissue encapsulation of the LP, Parsonnet pouch use, or S-ICD system migration (no/ minimal migration vs. moderate/significant migration) were significant predictors of DDC performance at the subject's termination time point. Results DDC was successful for each tested posture and time point for all subjects (n=37), with 355 tests in Left Lateral (LL), 371 tests in Dorsal (D), and 355 tests in Right Lateral (RL). Follow up data are available up to 18 months for 19 subjects at the time of this abstract; additional follow-up data will be added to the analysis for presentation. Communication thresholds decreased between 0 days and 3 days (LL P Conclusion Longitudinal studies demonstrate low and stable communication thresholds of a novel mCRM system over time for all three tested postures, regardless of factors such as LP encapsulation, Parsonnet pouch use, or S-ICD system migration. Device Communication Threshold Stability Funding Acknowledgement Type of funding source: Private company. Main funding source(s): Boston Scientific

Contains fulltext : 225390.pdf (Publisher’s version ) (Open Access) BACKGROUND: The subcutaneous implantable cardioverter-defibrillator (ICD) was designed to avoid complications related to the transvenous ICD lead by using an entirely extrathoracic placement. Evidence comparing these systems has been based primarily on observational studies. METHODS: We conducted a noninferiority trial in which patients with an indication for an ICD but no indication for pacing were assigned to receive a subcutaneous ICD or transvenous ICD. The primary end point was the composite of device-related complications and inappropriate shocks; the noninferiority margin for the upper boundary of the 95% confidence interval for the hazard ratio (subcutaneous ICD vs. transvenous ICD) was 1.45. A superiority analysis was prespecified if noninferiority was established. Secondary end points included death and appropriate shocks. RESULTS: A total of 849 patients (426 in the subcutaneous ICD group and 423 in the transvenous ICD group) were included in the analyses. At a median follow-up of 49.1 months, a primary end-point event occurred in 68 patients in the subcutaneous ICD group and in 68 patients in the transvenous ICD group (48-month Kaplan-Meier estimated cumulative incidence, 15.1% and 15.7%, respectively; hazard ratio, 0.99; 95% confidence interval [CI], 0.71 to 1.39; P = 0.01 for noninferiority; P = 0.95 for superiority). Device-related complications occurred in 31 patients in the subcutaneous ICD group and in 44 in the transvenous ICD group (hazard ratio, 0.69; 95% CI, 0.44 to 1.09); inappropriate shocks occurred in 41 and 29 patients, respectively (hazard ratio, 1.43; 95% CI, 0.89 to 2.30). Death occurred in 83 patients in the subcutaneous ICD group and in 68 in the transvenous ICD group (hazard ratio, 1.23; 95% CI, 0.89 to 1.70); appropriate shocks occurred in 83 and 57 patients, respectively (hazard ratio, 1.52; 95% CI, 1.08 to 2.12). CONCLUSIONS: In patients with an indication for an ICD but no indication for pacing, the subcutaneous ICD was noninferior to the transvenous ICD with respect to device-related complications and inappropriate shocks. (Funded by Boston Scientific; PRAETORIAN ClinicalTrials.gov number, NCT01296022.).

Background Poor medication adherence is wide-spread and associated with poor clinical outcomes. Herein, we introduce the Medication Adherence Score, a predictive analytic tool designed to provide clinicians insight into adherence behavior over the subsequent twelve months. The aim of the study was to demonstrate the feasibility of such scoring of patients at the individual level. Methods This is a single arm, non-randomized, 2-center, retrospective cohort study conducted among patients diagnosed with atrial fibrillation. The model, developed by Fair Isaac Corporation on pharmacy refill data, predicts adherence behavior to cardiovascular drugs using demographic, geographic and socio-economic predictors. The primary outcome was the number of patients that could be scored at the individual level without reliance on past individual refill behavior. The score was normalized between zero (lowest adherence score) and one (highest adherence score) and patients were grouped: low adherence 0.8. The institutional review board approved the study. Results A total of 1110 patients were included in the study with a median age of 71 (IQR 63, 79). Most patients (807, 73%) could be scored at the patient level, and the remaining patients (303, 27%) were scored based on characteristics associated with the geography of their home address. There were 488 patients (44%) with a high adherence score (score > 0.8), 382 (34%) with an intermediate adherence score (score between 0.6 and 0.8) and 240 patients (22%) with a low score. Younger patients had on average lower scores than older patients, and males also had higher scores. Conclusions The Medication Adherence Score was successfully applied to an unselected group of atrial fibrillation patients: nearly a quarter of the cohort were identified as at risk for non-adherence. Future studies are necessary to assess the association of this predictive analytic model with clinical outcomes.

Funding Acknowledgements This study was financially supported by Boston Scientific The influence of anesthesia technique on the outcomes of subcutaneous implantable cardioverter defibrillator (SICD) implantation has not been prospectively evaluated. The aim of the present analysis was to characterize the effect of anesthesia choice acutely and over a year follow-up in the large "real-world" cohort of the SICD Post Approval Study (SICD-PAS). Patients received either general anesthesia (GA), conscious sedation (CS), or monitored anesthesia care (MAC) at the implanting physicians" discretion. Acute results and complications over one year were compared between GA, CS and MAC. 1,631 patients were studied. 64.3% received GA , 29.2% received CS and 6.6% received MAC. Procedure times were shortest for MAC versus GA and CS (Table 1). Cross-over from CS and MAC to GA occurred in 2.9% and 1.9% of procedures, respectively. The mean left ventricular ejection fraction (LVEF) was lower in the MAC cohort compared with GA and CS. GA patients were less often discharged the same day than CS and MAC. Patients who had GA were more likely to have had intra-operative DFT testing, while successful DFT testing at implant did not differ among groups (Table 1). At one year, freedom from total complications did not differ between groups (93.3% for GA, 92.9% for CS and 87.8% for MAC, p = 0.095) nor did freedom from inappropriate shocks (94% for GA, 94.2% for CS, 88.9% for MAC, p = 0.138) nor appropriate shocks (95.8% for GA, 95% for CS, 95% for MAC, p = 0.747). All three anesthesia techniques had similar acute and one year outcomes but, despite having worse LVEF, patients who received MAC had shorter procedure times and infrequently required conversion to GA. GA was associated with higher rates of next day patient discharge. These results suggest that MAC may be preferred for the majority of patients. This observation should be confirmed with prospective trials. Table 1:Characteristics and Outcomes Parameter Conscious Sedation General Anesthesia Monitored Anesthesia Care P value Gender[%(N/Total)] Male 68.1 (324/476) 69.3 (726/1048) 66.4 (71/107) 0.77 Age (years) mean ± SD 54 ± 15 53 ± 15 54 ± 13 0.61 Body Mass Index mean ± SD 30 ± 7 30 ± 8 29 ± 6 0.41 Creatinine (mg/dL) mean ± SD 2 ± 2 2 ± 4 2 ± 2 0.43 LVEF (%) mean ± SD 33 ± 15 32 ± 15 26 ± 9

Patients with chronic renal disease on hemodialysis (HD) have limited vascular access and are at high risk of bacteremia. The subcutaneous implantable cardioverter-defibrillator (S-ICD) avoids vascular access, so it may be advantageous in this patient population.The purpose of this study was to report outcomes of patients with end-stage renal disease enrolled in the multicenter S-ICD post-approval study (PAS).S-ICD PAS patients were stratified on the basis of the presence (group 1) or absence (group 2) of HD at the time of implantation. Baseline demographic and clinical characteristics were collected. Perioperative and intermediate-term outcomes 365 days postimplantation were compared between the 2 groups.There were 220 patients on HD (13.4%) at the time of implantation out of 1637 patients enrolled in the S-ICD PAS. Patients on HD (group 1) were older (57.4 ± 13.2 years vs 52.5 ± 15.2 years; P .0001), more likely to be of African descent (48.6% vs 25.1%; P.0001), and had lower ejection fraction (28.6% ± 11.3% vs 32.6% ± 14.9%; P.0001) as compared with patients not on HD (group 2). Group 1 had more comorbidities and mortality was higher (17.4% vs 3.7%) than did group 2. The rate of complications calculated using the Kaplan-Meier estimate did not differ between the 2 groups (overall P = .9169), with a 1-year rate of 7.9% and 7.7% for groups 1 and 2, respectively. The rate of appropriate shocks was significantly higher in group 1 (Kaplan-Meier analysis, P = .0003), as was inappropriate shocks (P = .0137).S-ICD is associated with similar adverse event rates but a higher risk of inappropriate and appropriate therapy in dialysis patients than in nondialysis patients.

This study evaluated spontaneous arrhythmias and clinical outcomes in the S-ICD System PAS (Subcutaneous Implantable Cardioverter-Defibrillator Post Approval Study) cohort.The U.S. S-ICD PAS trial patient population more closely resembles transvenous ICD cohorts than earlier studies, which included many patients with little structural heart disease and few comorbidities. Early outcomes and low peri-operative complication rates were demonstrated in the S-ICD PAS cohort, but there are no data detailing spontaneous arrhythmias and clinical outcomes.The S-ICD PAS prospective registry included 1,637 de novo patients from 86 U.S. centers. Descriptive statistics, Kaplan-Meier time to event, and multivariate logistic regression were performed using data out to 365 days.Patients (68.5% men; mean ejection fraction of 32.0%; 42.9% ischemic; 13.4% on dialysis) underwent implantation for primary (76.6%) or secondary prevention indication. The complication-free rate was 92.5%. The appropriate shock (AS) rate was 5.3%. A total of 395 ventricular tachycardia (VT) or fibrillation (VF) episodes were appropriately sensed, with 131 (33.2%) self-terminating. First and final shock efficacy (up to 5 shocks) for the 127 discrete AS episodes were 91.3% and 100.0%, respectively. Discrete AS episodes included 67 monomorphic VT (MVT) and 60 polymorphic VT (PVT)/VF, with first shock efficacy of 95.2% and 86.7%, respectively. There were 19 storm events in 18 subjects, with 84.2% conversion success. Storm episodes were more likely PVT/VF (98 of 137).In the first year after implantation, a predominantly primary prevention population with low ejection fraction demonstrated a high complication-free rate and spontaneous event shock efficacy for MVT and PVT/VF arrhythmias at rapid ventricular rates. (Subcutaneous Implantable Cardioverter-Defibrillator System Post Approval Study [S-ICD PAS; NCT01736618).

Background and objective Worldwide adoption of the subcutaneous implantable cardioverter-defibrillator (S-ICD) for preventing sudden cardiac death continues to increase, as longer-term evidence demonstrating the safety and efficacy of the S-ICD expands. As a relatively new technology, comprehensive anesthesia guidance for the management of patients undergoing S-ICD placement is lacking. This article presents advantages and disadvantages of different periprocedural sedation and anesthesia options for S-ICD implants including general anesthesia, monitored anesthesia care, regional anesthesia, and nonanesthesia personnel administered sedation and analgesia. Methods Guidance, for approaches to anesthesia care during S-ICD implantation, is presented based upon literature review and consensus of a panel of high-volume S-ICD implanters, a regional anesthesiologist, and a cardiothoracic anesthesiologist with significant S-ICD experience. The panel developed suggested actions for perioperative sedation, anesthesia, surgical practices, and a decision algorithm for S-ICD implantation. Conclusions While S-ICD implantation currently requires higher sedation than transvenous ICD systems, the panel consensus is that general anesthesia is not required or is obligatory for the majority of patients for the experienced S-ICD implanter. The focus of the implanting physician and the anesthesia services should be to maximize patient comfort and take into consideration patient-specific comorbidities, with a low threshold to consult the anesthesiology team.

Background: Most inappropriate shocks from the subcutaneous implantable cardioverter-defibrillator (S-ICD) are caused by cardiac oversensing. A novel sensing methodology, SMART Pass (SP; Boston Scientific Corporation, Natick, MA), aims to reduce cardiac oversensing. Objective: The purpose of this study was to evaluate the effect of SP on shocks in ambulatory patients with S-ICD. Methods: Patients implanted in 2015–2016 and enrolled in a remote patient monitoring system were included and followed for 1 year. Shocks were adjudicated by 3 independent blinded reviewers as appropriate or inappropriate. Shock incidence was calculated for patients with SP programmed enabled or disabled at implantation, censoring patients when SP programming changed or at the last transmission. The SP setting (enabled vs disabled) was modeled as a time-dependent Cox regression variable. Results: The cohort consisted of 1984 patients, and a total of 880 shocks were adjudicated. At implantation, SP was enabled in 655 patients (33%) and disabled in 1329 patients (67%). SP reduced the risk for the first inappropriate shock by 50% (P

Objectives This study sought to report mechanisms of ventricular tachycardia (VT) and outcomes of VT ablation in patients with a left ventricular assist device (LVAD) as destination therapy. Background Continuous flow LVAD implantation plays a growing role in the management of end-stage heart failure, and VT is common. There are limited reports of VT ablation in patients with a destination LVAD. Methods Patients with a continuous-flow LVAD referred for VT ablation from 2010 to 2016 were analyzed retrospectively. Baseline patient characteristics, procedural data, and clinical follow-up were evaluated. Arrhythmia-free survival was assessed. Results Twenty-one patients (90% male, 62 ± 10 years) underwent catheter ablation of VT at a median of 191 days (interquartile range: 55 to 403 days) after LVAD implantation (15 HeartMate II, 6 HeartWare HVAD). Five patients (24%) had termination (n = 4) or slowing (n = 1) of VT with ablation near the apical inflow cannula, and 3 (14%) had bundle-branch re-entry. Freedom from recurrent VT among surviving patients was 64% at 1 year, with overall survival 67% at 1 year for patients without arrhythmia recurrence and 29% for patients with recurrence (p = 0.049). One patient had suspected pump thrombosis within 30 days of the ablation procedure, with no other major acute complications. Conclusions In this relatively large, single-center experience of VT ablation in destination LVAD, freedom from recurrent VT and implantable cardioverter-defibrillator shocks was associated with improved 1-year survival. Bundle branch re-entry was more prevalent than anticipated, and cannula-adjacent VT was less common. This challenging population remains at risk for late pump thrombosis and mortality.

Background The UNTOUCHED study will assess the safety and efficacy of the subcutaneous implantable cardioverter defibrillator (S-ICD) in the most common cohort of patients receiving ICDs. The primary goal is to evaluate the inappropriate shock (IAS)-free rate in primary prevention patients with a reduced ejection fraction (EF) and compare with a historical control of transvenous ICD patients with similar programming. Methods and Results The UNTOUCHED study is a global, multicenter, prospective, nonrandomized study of patients undergoing de novo S-ICD implantation for primary prevention of sudden cardiac death with a left ventricular EF ≤35%. The primary end point of this trial is freedom from IAS at 18 months. The lower 95% confidence bound of the observed incidence will be compared to a performance goal of 91.6%, which was derived from the IAS rate in MADIT-RIT. The secondary end points are all-cause shock-free rate at 18 months, and system- and procedure-related complication-free rate at 1 month and 6 months. Enrollment of a minimum of 1,100 subjects from up to 200 centers worldwide is planned based on power calculations of the primary and principal secondary end points. Conclusions This trial will provide important data regarding the rates of inappropriate and appropriate shock therapy in real-world use of the S-ICD in the most common group of patients receiving ICDs.

Objectives This study was conceived to determine the safety and efficacy of the subcutaneous implantable cardioverter-defibrillator (S-ICD) in patients with congenital heart disease (CHD). Background The S-ICD is a treatment option for patients with CHD in which a transvenous device is contraindicated due to anatomic considerations. However, efficacy in this group has not been determined. Methods A pooled analysis of 865 patients in the EFFORTLESS (Evaluation of Factors Affecting the Clinical Outcome and Cost-Effectiveness) registry (an international observational database) and a U.S. Investigational Device Exemption study were reviewed. Results Nineteen CHD patients versus 846 non-CHD patients with a median follow-up of 567 days and 639 days, respectively, were included. There were no deaths and no appropriate shocks for ventricular tachycardia/ventricular fibrillation in the CHD cohort, versus 26 deaths (3.1%, p = 0.42) and 111 appropriate shocks in 59 patients (7.1%) in the non-CHD cohort (p = 0.23). There were similar complication rates for the CHD versus non-CHD groups (10.5 vs. 9.6% [p = 0.89]), with inappropriate shocks for T-wave oversensing as the only complication in the CHD group (n = 2). The rate of inappropriate shocks was similar for both groups (10.5% vs. 10.9% [p = 0.96]). Successful defibrillation testing at 80J was comparable for the CHD versus non-CHD groups (100% vs. 98.5%). Conclusions The overall analysis of the CHD cohort from the pooled data of the Investigational Device Exemption study and the EFFORTLESS registry shows that the S-ICD is a safe option in CHD patients deemed to be at high risk for sudden cardiac death who do not have pacing indications. Further research to accurately define sudden cardiac death risk in the diverse anatomic substrates of CHD patients is warranted.

In transvenous implantable cardioverter-defibrillator (TV-ICD) implants, routine defibrillation testing (DFT) does not improve shock efficacy or reduce arrhythmic death but patients are exposed to the risk of complications related to DFT. The conversion rate of DFT in subcutaneous ICD (S-ICD) is high and first shock efficacy is similar to TV-ICD efficacy rates. STUDY DESIGN: The PRAETORIAN-DFT trial is an investigator-initiated, randomized, controlled, multicenter, prospective two-arm trial designed to demonstrate non-inferiority of omitting DFT in patients undergoing S-ICD implantation in which the S-ICD system components are optimally positioned. Positioning of the S-ICD will be assessed with the PRAETORIAN score. The PRAETORIAN score is developed to systematically evaluate implant position of the S-ICD system components which determine the defibrillation threshold on post-operative chest X-ray. A total of 965 patients, scheduled to undergo a de novo S-ICD implantation without contra-indications for either DFT strategy, will be randomized to either standard of care S-ICD implantation with DFT, or S-ICD implantation without DFT but with evaluation of the implant position using the PRAETORIAN score. The study is powered to claim non-inferiority of S-ICD implantation without DFT in de novo S-ICD patients in respect to the primary endpoint of first shock efficacy in spontaneous arrhythmia episodes. Patients with a high PRAETORIAN score (≥90) in the interventional arm of this study will undergo DFT according to the same DFT protocol as in the control arm. CONCLUSION: The PRAETORIAN-DFT trial is a randomized trial that aims to gain scientific evidence to safely omit a routine DFT after S-ICD implantation in patients with correct device positioning.

Background: A completely extracardiac pacing system provides the potential for clinical advantages over existing device alternatives that require intravascular, endocardial, or epicardial contact. Preliminary studies evaluating the feasibility of cardiac pacing with a lead in the anterior mediastinum, outside the pericardium and circulatory system have been completed. These studies examined (1) the anatomic access route, (2) the usability of a delivery tool to facilitate lead placement, and (3) the pacing performance of the extracardiac lead. Methods: Feasibility evaluations included (1) a retrospective computed tomography analysis to characterize anatomic variations related to lead access, (2) accessing the anterior mediastinum in cadavers and human subjects using a custom delivery tool, and (3) acute clinical pacing performance. Results: Major findings: (1) A total of 166 (95%) out of 174 patients had a viable lead access path through the fourth, fifth, or sixth intercostal space. (2) Access to the targeted implant location using a delivery tool was successful in all 5 cadavers and 3 humans without use of fluoroscopy and with an average lead delivery time of 121±52 s. No damage to the lung, pericardium, heart, or internal thoracic vessels occurred. (3) Pacing performance was tested in 6 human subjects showing a threshold voltage of 4.7 V (2.7–6.7), threshold pulse width of 1.8 ms (1.0–2.5), and an impedance of 1205 Ω (894–1786). R-wave amplitudes measured 9.6 mV (5.6–12.0). Conclusions: Results support the feasibility for this completely extracardiac pacing method in a heterogeneous patient population, using a minimally invasive, parasternal, delivery approach and with adequate sensing and thresholds suited for temporary pacing.

Background The subcutaneous implantable cardioverter-defibrillator (S-ICD) has shown favorable outcomes in large registries with broad inclusion criteria. The cohorts reported had less heart disease and fewer comorbidities than standard ICD populations. Objective The purpose of this study is to characterize acute performance for primary prevention patients with a left ventricular ejection fraction (LVEF) ≤35% (primary prevention ≤35%). Methods Primary prevention ≤35% patients with no prior documented sustained ventricular tachycardia (VT), pacing indication, end-stage heart failure, or advanced renal failure were prospectively enrolled. Analyses included descriptive statistics, Kaplan-Meier time to event, and multivariable linear and logistic regression. Results In 1112 of 1116 patients, an S-ICD was successfully implanted (99.6%). Predictors for longer procedure time included 3-incision technique, higher body mass index (BMI), performing defibrillation testing (DFT), imaging, younger age, black race, and European vs North American centers. Patients undergoing DFT (82%) were successfully converted (99.2%; 93.5% converting at ≤65 J). Higher BMI was predictive of failing DFT at ≤65 J. The rate of 30-day freedom from complications was 95.8%. Most complications involved postoperative healing (45%) or interventions after DFT or impedance check (19%). Conclusion The procedural outcome data of UNTOUCHED reinforce that S-ICD therapy has low perioperative complication rates and high conversion efficacy of induced ventricular fibrillation, even in a higher-risk cohort with low LVEF and more comorbidities than previous S-ICD studies. Higher BMI warrants more careful attention to implant technique.

Background: The ability to predict defibrillation efficacy at the time of subcutaneous implantable cardioverter-defibrillator implantation without the need to induce ventricular fibrillation might eliminate the need for defibrillation testing. The purpose of this study was to determine the association of high-voltage impedance and system implant position on ventricular fibrillation conversion success with a submaximal 65-J shock. Methods: In the subcutaneous implantable cardioverter-defibrillator IDE study (Investigational Device Exemption), a successful conversion test required 2 consecutive ventricular fibrillation conversions at 65 J in either shock vector. Chest radiographs were obtained after implantation. Patients with imaging and impedance data were included. Suboptimal device position was defined as an inferior electrode or pulse generator or electrode coil depth >3 mm anterior to the sternum. Absence of suboptimal positional parameters was defined as appropriate position. Conversion success rate was calculated among all 65-J tests. Results: Of 314 patients who underwent subcutaneous implantable cardioverter-defibrillator implantation, 282 patients were included in this analysis. There were 637 inductions to test defibrillation at 65 J. Sixty-two conversion failures (9.7%) occurred in 42 (14.9%) patients. Lower body mass index and lower shock impedance were associated with higher conversion success rate, whereas white race was associated with lower conversion success rate. Suboptimal position was more common in obese patients. Inferior electrode and greater distance between the lead and sternum were associated with a higher impedance. When appropriate system position was achieved, conversion failure was not associated with high body mass index. Conclusions: Subcutaneous implantable cardioverter-defibrillator shock efficacy is associated with system position and high-voltage system impedance. A high impedance is associated with inferiorly placed pulse generator and electrode system, inadequate coil depth, and a lower rate of defibrillator success. Clinical Trial Registration: URL: https://www.clinicaltrials.gov . Unique identifier: NCT01064076.

Aims The development of communicating modular cardiac rhythm management systems relies on effective intrabody communication between a subcutaneous implantable cardioverter-defibrillator (S-ICD) and a leadless pacemaker (LP), using conducted communication. Communication success is affected by the LP and S-ICD orientation. This study is designed to evaluate the orientation of the LP and S-ICD in canine subjects and measure success and threshold of intrabody communication. To gain more human insights, we will explore device orientation in LP and S-ICD patients. Methods and results Canine subjects implanted with a prototype S-ICD and LP (both Boston Scientific, MA, USA) with anterior-posterior fluoroscopy images were included in this analysis. For comparison, a retrospective analysis of human S-ICD and LP patients was performed. The angle of the long axis of the LP towards the vertical axis of 0°, and distance between the coil and LP were measured. Twenty-three canine subjects were analysed. Median angle of the LP was 29° and median distance of the S-ICD coil to LP was 0.8 cm. All canine subjects had successful communication. The median communicating threshold was 2.5 V. In the human retrospective analysis, 72 LP patients and 100 S-ICD patients were included. The mean angle of the LP was 56° and the median distance between the S-ICD coil and LP was 4.6 cm. Conclusion Despite the less favourable LP orientation in canine subjects, all communication attempts were successful. In the human subjects, we observed a greater and in theory more favourable LP angle towards the communication vector. These data suggests suitability of human anatomy for conductive intrabody communication.

Objectives This study determined whether obesity increased the risk of failed shocks and complications among subcutaneous implantable cardioverter-defibrillator (S-ICD) recipients. Background The S-ICD is an established treatment for patients at high risk for ventricular arrhythmias. Obesity may increase the transvenous defibrillation threshold and the rate of complications. Methods We analyzed data from the 321 patients enrolled in the S-ICD Investigational Device Exemption (IDE) study. They were categorized into 3 body mass index (BMI) groups: 2 (underweight and normal), 25 to 30 kg/m 2 (overweight), and >30 kg/m 2 (obese). Patients underwent implantation followed by defibrillation testing at 65 J. Chronic defibrillation testing was repeated >150 days post-implantation in a subset of patients. Results Seventy-nine patients had BMI 2 , 105 had BMI 25 to 30 kg/m 2 , and 137 had BMI >30 kg/m 2 . A failed first shock of any kind occurred in 52 patients, including 41 patients during implant defibrillation testing, 11 patients during chronic defibrillation testing, and 5 patients during spontaneous ventricular arrhythmias. The rate of failed first shocks during implant defibrillation testing increased across BMI categories (5.1% among underweight and normal patients, 13.3% among overweight patients, and 16.9% among obese patients; p = 0.04). Among obese patients, shock impedance was higher during failed first shocks than successful first shocks (103.5 ohms vs. 84.6 ohms; p = 0.001). The rate of failed first shocks during chronic defibrillation testing and spontaneous ventricular arrhythmias did not significantly differ among BMI groups, nor did the rate of complications. Of the 8 underweight patients, there were no failed shocks or complications. Conclusions Obese patients are at increased risk of failed first S-ICD shocks during defibrillation testing. Whether this can be overcome by optimal implantation techniques remains unknown. Rates of complications were not increased among obese patients.

Background The entirely subcutaneous implantable cardioverter-defibrillator (S-ICD) is the first implantable defibrillator that avoids placing electrodes in or around the heart. Two large prospective studies (IDE [S-ICD System IDE Clinical Investigation] and EFFORTLESS [Boston Scientific Post Market S-ICD Registry]) have reported 6-month to 1-year data on the S-ICD. Objectives The objective of this study was to evaluate the safety and efficacy of the S-ICD in a large diverse population. Methods Data from the IDE and EFFORTLESS studies were pooled. Shocks were independently adjudicated, and complications were measured with a standardized classification scheme. Enrollment date quartiles were used to assess event rates over time. Results Eight hundred eighty-two patients who underwent implantation were followed for 651 ± 345 days. Spontaneous ventricular tachyarrhythmia (VT)/ventricular fibrillation (VF) events (n = 111) were treated in 59 patients; 100 (90.1%) events were terminated with 1 shock, and 109 events (98.2%) were terminated within the 5 available shocks. The estimated 3-year inappropriate shock rate was 13.1%. Estimated 3-year, all-cause mortality was 4.7% (95% confidence interval: 0.9% to 8.5%), with 26 deaths (2.9%). Device-related complications occurred in 11.1% of patients at 3 years. There were no electrode failures, and no S-ICD–related endocarditis or bacteremia occurred. Three devices (0.3%) were replaced for right ventricular pacing. The 6-month complication rate decreased by quartile of enrollment (Q1: 8.9%; Q4: 5.5%), and there was a trend toward a reduction in inappropriate shocks (Q1: 6.9% Q4: 4.5%). Conclusions The S-ICD demonstrated high efficacy for VT/VF. Complications and inappropriate shock rates were reduced consistently with strategic programming and as operator experience increased. These data provide further evidence for the safety and efficacy of the S-ICD. (Boston Scientific Post Market S-ICD Registry [EFFORTLESS]; NCT01085435 ; S-ICD® System IDE Clinical Study; NCT01064076 )

A New Algorithm to Reduce Inappropriate Therapy Introduction The subcutaneous ICD system (S-ICD) has been shown to be a safe and effective treatment for patients at risk for sudden cardiac death. This device reliably detects ventricular tachyarrhythmias with a low incidence of inappropriate shocks for supraventricular arrhythmias. However, T-wave oversensing (TWOS) is more common with the S-ICD compared with transvenous systems. We developed a novel discrimination algorithm to reduce TWOS without compromising tachyarrhythmia discrimination. Methods and Results The algorithm was developed using a database of recorded episodes, including 244 appropriate therapies for ventricular arrhythmias and 133 episodes with an inappropriate detection due to TWOS, and using a computer model that simulates the S-ICD system. An independent set of data of 161 TWOS episodes, 137 ventricular and 328 supraventricular episodes, was used to validate the algorithm on actual device hardware. The S-ICD performance with the new algorithm was compared with the S-ICD without the new algorithm. Development results showed a decrease in inappropriate charge due to TWOS by 30.7 ± 18%. All ventricular arrhythmias were appropriately detected and the time to appropriate charge initiation was not increased. System validation showed that the new algorithm avoided an inappropriate charge due to TWOS by 39.8 ± 11.4%. No decrease in ventricular arrhythmia sensitivity and no significant change in supraventricular specificity were observed. Conclusions A new algorithm that uses correlation of the existing complex to previous complexes reduced TWOS episodes by approximately 40%. The algorithm has potential for a clinically meaningful decrease in inappropriate shocks.

Background The subcutaneous implantable cardioverter-defibrillator (S-ICD) was developed to reduce short- and long-term complications associated with transvenous ICD leads. Early multicenter studies included younger patients with less left ventricular systolic dysfunction and fewer comorbidities than cohorts with traditional ICD. Objective The purpose of this study was to characterize patient selection and the acute performance of the S-ICD in a contemporary real-world setting. Methods The S-ICD Post-Approval Study is a prospective registry involving 86 US centers. Patients were enrolled if they met criteria for S-ICD implantation, passed an electrocardiogram screening test, and had a life expectancy of >1 year. Analyses of descriptive statistics, Kaplan-Meier time to event, and multivariate logistic regression were performed. Results The study includes 1637 patients who underwent S-ICD implantation. The cohort included 68.6% (1123/1637) male patients, and 13.4% (220/1636) were receiving dialysis for end-stage renal disease. The mean age was 52 ± 15 years, with a mean left ventricular ejection fraction of 32.0% ± 14.6%. Electrocardiogram screening was successful for at least 1, 2, or 3 vectors in 100%, 93.8%, and 51.4% of patients, respectively. Medical imaging (65.1%, 1065/1636) and general anesthesia (64.1%, 1048/16) were used in a majority of patients, and 52.2% (855/1637) were implanted with the 2-incision technique. Induced ventricular tachycardia/ventricular tachycardia was successfully converted in 98.7% (1394/1412) of patients. The 30-day complication-free rate was 96.2%. Predictors of complications included diabetes, younger age, and higher body mass index. Conclusion Contemporary US patients with S-ICD have more comorbidities than do previous cohorts with S-ICD, but they are younger with more end-stage renal disease than do patients with transvenous ICD. Implantation success is high, and short-term complication rates are acceptable.

Objectives The primary objective was to assess the acute and 3-month performance of the modular antitachycardia pacing (ATP)-enabled leadless pacemaker (LP) and subcutaneous implantable cardioverter-defibrillator (S-ICD) system, particularly device–device communication and ATP delivery. Background Transvenous pacemakers and implantable cardioverter-defibrillators (ICDs) have considerable rates of lead complications. We examined the next step in multicomponent leadless cardiac rhythm management: feasibility of pacing (including ATP) by a LP, commanded by an implanted S-ICD through wireless, intrabody, device–device communication. Methods The combined modular cardiac rhythm management therapy system of the LP and S-ICD prototypes was evaluated in 3 animal models (ovine, porcine, and canine) both in acute and chronic (90 days) experiments. LP performance, S-ICD to LP communication, S-ICD and LP rhythm discrimination, and ATP delivery triggered by the S-ICD were tested. Results The LP and S-ICD were successfully implanted in 98% of the animals (39 of 40). Of the 39 animals, 23 were followed up for 90 days post-implant. LP performance was adequate and exhibited appropriate VVI behavior during the 90 days of follow-up in all tested animals. Unidirectional communication between the S-ICD and LP was successful in 99% (398 of 401) of attempts, resulting in 100% ATP delivery by the LP (10 beats at 81% of the coupling interval). Adequate S-ICD sensing was observed during normal sinus rhythm, LP pacing, and ventricular tachycardia/ventricular fibrillation. Conclusions This study presents the preclinical acute and chronic performance of the combined function of an ATP-enabled LP and S-ICD. Appropriate VVI functionality, successful wireless device–device communication, and ATP delivery were demonstrated by the LP. Clinical studies on safety and performance are needed.

Background The incidence, predictors, and impact of atrial arrhythmias along with left atrial structural changes in patients with left ventricular assist devices ( LVAD s) remain undetermined. Methods and Results All patients who underwent LVAD implantation from 2008 to 2015 at the University of Chicago Medical Center were included. Electronic medical records, electrocardiograms, echocardiograms, and cardiac electrical device interrogations were reviewed. The association of arrhythmias and clinical covariates with survival was evaluated by Kaplan–Meier and Cox proportional hazards analyses. A total of 331 patients were followed for a median of 330 days (range 0–2306 days). Mean age was 57.8±12.8 years, 256 participants (77.3%) were male, mean left ventricular ejection fraction was 20±6.6%, and 124 (37.5%) had ischemic cardiomyopathy. Atrial arrhythmias (53.8%) were highly prevalent and frequently coexisted before LVAD implantation: atrial fibrillation ( AF ) in 45.9%, atrial flutter in 13.9%, atrial tachycardia in 6.9%, and atrioventricular nodal reentrant tachycardia in 1.2%. New‐onset AF was documented in 14 patients (7.8% of patients without prior AF ) after the first 30 days with an LVAD . Increasing age, renal insufficiency, and lung disease were predictors of new‐onset AF after LVAD implantation. Of patients with paroxysmal AF , 43% had no further AF after LVAD . Left atrial size and volume index improved with LVAD ( P AF , atrial tachycardia, ventricular arrhythmia, coronary artery bypass, and low albumin were associated with decreased survival. Conclusions Atrial arrhythmias are significantly prevalent in patients who require LVAD and are associated with increased mortality; however, LVAD s induce favorable atrial structural and electrical remodeling.

This study sought to report mechanisms of ventricular tachycardia (VT) and outcomes of VT ablation in patients with a left ventricular assist device (LVAD) as destination therapy.Continuous flow LVAD implantation plays a growing role in the management of end-stage heart failure, and VT is common. There are limited reports of VT ablation in patients with a destination LVAD.Patients with a continuous-flow LVAD referred for VT ablation from 2010 to 2016 were analyzed retrospectively. Baseline patient characteristics, procedural data, and clinical follow-up were evaluated. Arrhythmia-free survival was assessed.Twenty-one patients (90% male, 62 ± 10 years) underwent catheter ablation of VT at a median of 191 days (interquartile range: 55 to 403 days) after LVAD implantation (15 HeartMate II, 6 HeartWare HVAD). Five patients (24%) had termination (n = 4) or slowing (n = 1) of VT with ablation near the apical inflow cannula, and 3 (14%) had bundle-branch re-entry. Freedom from recurrent VT among surviving patients was 64% at 1 year, with overall survival 67% at 1 year for patients without arrhythmia recurrence and 29% for patients with recurrence (p = 0.049). One patient had suspected pump thrombosis within 30 days of the ablation procedure, with no other major acute complications.In this relatively large, single-center experience of VT ablation in destination LVAD, freedom from recurrent VT and implantable cardioverter-defibrillator shocks was associated with improved 1-year survival. Bundle branch re-entry was more prevalent than anticipated, and cannula-adjacent VT was less common. This challenging population remains at risk for late pump thrombosis and mortality.

Background The subcutaneous implantable defibrillator (S-ICD) provides an alternative to the transvenous ICD for the prevention of sudden cardiac death, but has not been well studied in the most commonly treated transvenous ICD patient population, namely, primary prevention (PP) patients with left ventricular dysfunction. Objective The analyses in the present study were designed to compare clinical outcomes for PP patients with and without a reduced ejection fraction (EF) and secondary prevention (SP) patients implanted with the S-ICD. Methods All patients 18 years and older from the S-ICD IDE study and the EFFORTLESS Registry with available data as of November 18, 2013, were included (n = 856; mean follow-up duration 644 days). Outcomes were evaluated in 2 analyses: (1) comparing all PP patients (n = 603, 70.4%) with all SP patients (n = 253, 29.6%) and (2) comparing all PP patients with an EF ≤35% (n = 379) with those with an EF >35% (n = 149, 17.4%). Results No differences were observed in mortality, complications, inappropriate therapy, or ability to convert ventricular tachyarrhythmias between SP and PP patients. However, SP patients had a higher incidence of appropriate therapy than did PP patients (11.9% vs 5.0%; P = .0004). In the PP subanalysis, the cohort with an EF ≤35% had significantly older patients with more comorbidities and higher mortality (3.0% annually vs 0.0%). Despite these differences, device-related complications, conversion efficacy, and incidence of inappropriate shock therapies were not significantly different between PP subgroups. Conclusion The S-ICD performs well in protecting patients with either PP or SP implant indications from sudden cardiac death. Within PP patients, device performance was independent of EF.