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.).

Efficacy and Safety of Appropriate Shocks and Antitachycardia Pacing in Transvenous and Subcutaneous Implantable Defibrillators: Analysis of All Appropriate Therapy in the PRAETORIAN Trial.

BACKGROUND: The PRAETORIAN trial (A Prospective, Randomized Comparison of Subcutaneous and Transvenous Implantable Cardioverter Defibrillator Therapy) showed noninferiority of subcutaneous implantable cardioverter defibrillator (S-ICD) compared with transvenous implantable cardioverter defibrillator (TV-ICD) with regard to inappropriate shocks and complications. In contrast to TV-ICD, S-ICD cannot provide antitachycardia pacing for monomorphic ventricular tachycardia. This prespecified secondary analysis evaluates appropriate therapy and whether antitachycardia pacing reduces the number of appropriate shocks. METHODS: The PRAETORIAN trial was an international, investigator-initiated randomized trial that included patients with an indication for implantable cardioverter defibrillator (ICD) therapy. Patients with previous ventricular tachycardia <170 bpm or refractory recurrent monomorphic ventricular tachycardia were excluded. In 39 centers, 849 patients were randomized to receive an S-ICD (n=426) or TV-ICD (n=423) and were followed for a median of 49.1 months. ICD programming was mandated by protocol. Appropriate ICD therapy was defined as therapy for ventricular arrhythmias. Arrhythmias were classified as discrete episodes and storm episodes (≥3 episodes within 24 hours). Analyses were performed in the modified intention-to-treat population. RESULTS: In the S-ICD group, 86 of 426 patients received appropriate therapy, versus 78 of 423 patients in the TV-ICD group, during a median follow-up of 52 months (48-month Kaplan-Meier estimates 19.4% and 17.5%; P=0.45). In the S-ICD group, 83 patients received at least 1 shock, versus 57 patients in the TV-ICD group (48-month Kaplan-Meier estimates 19.2% and 11.5%; P=0.02). Patients in the S-ICD group had a total of 254 shocks, compared with 228 shocks in the TV-ICD group (P=0.68). First shock efficacy was 93.8% in the S-ICD group and 91.6% in the TV-ICD group (P=0.40). The first antitachycardia pacing attempt successfully terminated 46% of all monomorphic ventricular tachycardias, but accelerated the arrhythmia in 9.4%. Ten patients with S-ICD experienced 13 electrical storms, versus 18 patients with TV-ICD with 19 electrical storms. Patients with appropriate therapy had an almost 2-fold increased relative risk of electrical storms in the TV-ICD group compared with the S-ICD group (P=0.05). CONCLUSIONS: In this trial, no difference was observed in shock efficacy of S-ICD compared with TV-ICD. Although patients in the S-ICD group were more likely to receive an ICD shock, the total number of appropriate shocks was not different between the 2 groups. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT01296022.

Subcutaneous or Transvenous Defibrillator Therapy.

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.).

Device-related complications in subcutaneous versus transvenous ICD: a secondary analysis of the PRAETORIAN trial.

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.

Primary Results From the Understanding Outcomes With the S-ICD in Primary Prevention Patients With Low Ejection Fraction (UNTOUCHED) Trial.

BACKGROUND: The subcutaneous (S) implantable cardioverter-defibrillator (ICD) is safe and effective for sudden cardiac death prevention. However, patients in previous S-ICD studies had fewer comorbidities, had less left ventricular dysfunction, and received more inappropriate shocks (IAS) than in typical transvenous ICD trials. The UNTOUCHED trial (Understanding Outcomes With the S-ICD in Primary Prevention Patients With Low Ejection Fraction) was designed to evaluate the IAS rate in a more typical, contemporary ICD patient population implanted with the S-ICD using standardized programming and enhanced discrimination algorithms. METHODS: Primary prevention patients with left ventricular ejection fraction ≤35% and no pacing indications were included. Generation 2 or 3 S-ICD devices were implanted and programmed with rate-based therapy delivery for rates ≥250 beats per minute and morphology discrimination for rates ≥200 and <250 beats per minute. Patients were followed for 18 months. The primary end point was the IAS-free rate compared with a 91.6% performance goal, derived from the results for the ICD-only patients in the MADIT-RIT study (Multicenter Automatic Defibrillator Implantation Trial-Reduce Inappropriate Therapy). Kaplan-Meier analyses were performed to evaluate event-free rates for IAS, all-cause shock, and complications. Multivariable proportional hazard analysis was performed to determine predictors of end points. RESULTS: S-ICD implant was attempted in 1116 patients, and 1111 patients were included in postimplant follow-up analysis. The cohort had a mean age of 55.8±12.4 years, 25.6% were women, 23.4% were Black, 53.5% had ischemic heart disease, 87.7% had symptomatic heart failure, and the mean left ventricular ejection fraction was 26.4±5.8%. Eighteen-month freedom from IAS was 95.9% (lower confidence limit, 94.8%). Predictors of reduced incidence of IAS were implanting the most recent generation of device, using the 3-incision technique, no history of atrial fibrillation, and ischemic cause. The 18-month all-cause shock-free rate was 90.6% (lower confidence limit, 89.0%), meeting the prespecified performance goal of 85.8%. Conversion success rate for appropriate, discrete episodes was 98.4%. Complication-free rate at 18 months was 92.7%. CONCLUSIONS: This study demonstrates high efficacy and safety with contemporary S-ICD devices and programming despite the relatively high incidence of comorbidities in comparison with earlier S-ICD trials. The inappropriate shock rate (3.1% at 1 year) is the lowest reported for the S-ICD and lower than many transvenous ICD studies using contemporary programming to reduce IAS. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT02433379.

Outcomes of two versus three incision techniques: Results from the subcutaneous ICD post-approval study.

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 < .0001). No other differences in outcomes were observed between the two groups, including rates of infection, electrode migration, inappropriate shocks and first shock efficacy for treating ventricular arrhythmias. CONCLUSION: In this large cohort of patients implanted with an S-ICD and followed for 3 years the 2IT was as safe and effective as the 3IT while significantly reducing procedure time.

Rationale and design of the PRAETORIAN-DFT trial: A prospective randomized CompArative trial of SubcutanEous ImplanTable CardiOverter-DefibrillatoR ImplANtation with and without DeFibrillation testing.

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.

Device orientation of a leadless pacemaker and subcutaneous implantable cardioverter-defibrillator in canine and human subjects and the effect on intrabody communication.

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.

Anesthesia for subcutaneous implantable cardioverter-defibrillator implantation: Perspectives from the clinical experience of a U.S. panel of physicians.

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.

The Design of the Understanding Outcomes with the S-ICD in Primary Prevention Patients with Low EF Study (UNTOUCHED).

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.

The learning curve associated with the introduction of the subcutaneous implantable defibrillator.

AIMS: The subcutaneous implantable cardioverter defibrillator (S-ICD) was introduced to overcome complications related to transvenous leads. Adoption of the S-ICD requires implanters to learn a new implantation technique. The aim of this study was to assess the learning curve for S-ICD implanters with respect to implant-related complications, procedure time, and inappropriate shocks (IASs). METHODS AND RESULTS: In a pooled cohort from two clinical S-ICD databases, the IDE Trial and the EFFORTLESS Registry, complications, IASs at 180 days follow-up and implant procedure duration were assessed. Patients were grouped in quartiles based on experience of the implanter and Kaplan-Meier estimates of complication and IAS rates were calculated. A total of 882 patients implanted in 61 centres by 107 implanters with a median of 4 implants (IQR 1,8) were analysed. There were a total of 59 patients with complications and 48 patients with IAS. The complication rate decreased significantly from 9.8% in Quartile 1 (least experience) to 5.4% in Quartile 4 (most experience) (P = 0.02) and non-significantly for IAS from 7.9 to 4.8% (P = 0.10). Multivariable analysis demonstrated a hazard ratio of 0.78 (P = 0.045) for complications and 1.01 (P = 0.958) for IAS. Dual-zone programming increased with experience of the individual implanter (P < 0.001), which reduced IAS significantly in the multivariable model (HR 0.44, P = 0.01). Procedure time decreased from 75 to 65 min (P < 0.001). The complication rate and procedure time stabilized after Quartile 2 (>13 implants). CONCLUSION: There is a short and significant learning curve associated with physicians adopting the S-ICD. Performance stabilizes after 13 implants.

Late Manifestation of Coronary Sinus and Left Atrial Perforation of a Left Ventricular Pacemaker Lead at Extraction.

A 56-year-old man presented for lead extraction of a left ventricular (LV) lead that had been deactivated due to hiccups and of a right ventricular (RV) lead with a high threshold. Pus was noted upon entering the pocket. The right atrial and RV leads were extracted, but traction on the LV lead caused ischemia and was not performed. An echocardiogram demonstrated the lead in the left atrium and a robotic-assisted thoracotomy was used to remove the lead that had unroofed the coronary sinus, gone into the left atrium, and perforated through the free wall into the pericardium.

A new algorithm to reduce inappropriate therapy in the S-ICD system.

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.

In memoriam: A tribute to the work and lives of Ron Selvester and Rory Childers.

At the April, 2015 International Society for Computerized Electrocardiology (ISCE) Annual Conference in San Jose, CA, a special session entitled Remembering Ron & Rory was held to pay tribute to the extraordinary work and lives of two experts in electrocardiology. The session was well attended by conference attendees, Childers' family members and friends, and additional colleagues who traveled to San Jose solely to participate in this session. The purpose of the present paper is to document the spirit of this special session as faithfully as possible using the words of the session speakers.

Safety and efficacy of a totally subcutaneous implantable-cardioverter defibrillator.

BACKGROUND: The most frequent complications associated with implantable cardioverter-defibrillators (ICDs) involve the transvenous leads. A subcutaneous implantable cardioverter-defibrillator (S-ICD) has been developed as an alternative system. This study evaluated the safety and effectiveness of the S-ICD System (Cameron Health/Boston Scientific) for the treatment of life-threatening ventricular arrhythmias (ventricular tachycardia/ventricular fibrillation). METHODS AND RESULTS: This prospective, nonrandomized, multicenter trial included adult patients with a standard indication for an ICD, who neither required pacing nor had documented pace-terminable ventricular tachycardia. The primary safety end point was the 180-day S-ICD System complication-free rate compared with a prespecified performance goal of 79%. The primary effectiveness end point was the induced ventricular fibrillation conversion rate compared with a prespecified performance goal of 88%, with success defined as 2 consecutive ventricular fibrillation conversions of 4 attempts. Detection and conversion of spontaneous episodes were also evaluated. Device implantation was attempted in 321 of 330 enrolled patients, and 314 patients underwent successful implantation. The cohort was followed for a mean duration of 11 months. The study population was 74% male with a mean age of 52±16 years and mean left ventricular ejection fraction of 36±16%. A previous transvenous ICD had been implanted in 13%. Both primary end points were met: The 180-day system complication-free rate was 99%, and sensitivity analysis of the acute ventricular fibrillation conversion rate was >90% in the entire cohort. There were 38 discrete spontaneous episodes of ventricular tachycardia/ventricular fibrillation recorded in 21 patients (6.7%), all of which successfully converted. Forty-one patients (13.1%) received an inappropriate shock. CONCLUSIONS: The findings support the efficacy and safety of the S-ICD System for the treatment of life-threatening ventricular arrhythmias.

ICD lead parameters, performance, and adverse events following continuous-flow LVAD implantation.

BACKGROUND: Ventricular arrhythmias (VAs) in the months following continuous-flow left ventricular assist devices (LVADs) implantation are common and associated with increased morbidity and mortality. We sought to evaluate for changes in implantable cardioverter defibrillator (ICD) performance following LVAD implantation. METHODS: We retrospectively reviewed the ICD interrogation reports and medical records of patients who received a continuous-flow LVAD at the University of Chicago Medical Center between January 2008 and December 2010. Patients who did not have an ICD prior to LVAD implantation were excluded. RESULTS: Forty-four patients were included. Median right ventricular lead sensing amplitude decreased from 10.0 (interquartile range 7.6-13.6) mV prior to LVAD to 7.9 (5.9-9.3) mV after LVAD implantation (P < 0.01). Significant reductions in sensing threshold were associated with smaller lead diameters, smaller pace/sense electrode surface areas, and Medtronic ICD leads (Medtronic Inc., Minneapolis, MN, USA). Lead impedance and capture threshold did not change significantly. ICD-related adverse events occurred in 30% of patients and led to ICD modification in 18% of patients. CONCLUSIONS: Implantation of a continuous-flow LVAD is associated with changes in the performance of preexisting ICDs. ICD-related adverse events were encountered following LVAD implantation in this cohort, and at times resulted in invasive and noninvasive ICD system modification. Reductions in ICD sensing threshold after LVAD implantation may adversely affect ICD function. Formal ICD interrogation in addition to the regular follow-up testing is warranted post-LVAD.

Predictive value of the PRAETORIAN score for defibrillation test success in patients with subcutaneous ICD: A subanalysis of the PRAETORIAN-DFT trial.

BACKGROUND: The PRAETORIAN score estimates the risk of failure of subcutaneous implantable cardioverter-defibrillator (S-ICD) therapy by using generator and lead positioning on bidirectional chest radiographs. The PRospective randomized compArative trial of subcutanEous implanTable cardiOverter-defibrillatoR ImplANtation with and without DeFibrillation Testing (PRAETORIAN-DFT) investigates whether PRAETORIAN score calculation is noninferior to defibrillation testing (DFT) with regard to first shock efficacy in spontaneous events. OBJECTIVE: This prespecified subanalysis assessed the predictive value of the PRAETORIAN score for defibrillation success in induced ventricular arrhythmias. METHODS: This multicenter investigator-initiated trial randomized 965 patients between DFT and PRAETORIAN score calculation after de novo S-ICD implantation. Successful DFT was defined as conversion of induced ventricular arrhythmia in <5 seconds from shock delivery within 2 attempts. Bidirectional chest radiographs were obtained after implantation. The predictive value of the PRAETORIAN score for DFT success was calculated for patients in the DFT arm. RESULTS: In total, 482 patients were randomized to undergo DFT. Of these patients, 457 (95%) underwent DFT according to protocol, of whom 445 (97%) had successful DFT and 12 (3%) had failed DFT. A PRAETORIAN score of ≥90 had a positive predictive value of 25% for failed DFT, and a PRAETORIAN score of <90 had a negative predictive value of 99% for successful DFT. A PRAETORIAN score of ≥90 was the strongest independent predictor for failed DFT (odds ratio 33.77; confidence interval 6.13-279.95; P < .001). CONCLUSION: A PRAETORIAN score of <90 serves as a reliable indicator for DFT success in patients with S-ICD, and a PRAETORIAN score of ≥90 is a strong predictor for DFT failure.

Initial Experience With Intercostal Insertion of an Extravascular ICD Lead Compatible With Existing Pulse Generators.

BACKGROUND: This study assessed safety and feasibility of a novel extravascular 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. Currently available or investigational, extravascular-ICDs include a subcutaneous or subxiphoid lead connected to customized extravascular-ICD PGs. METHODS: This novel extravascular-ICD (AtaCor Medical Inc, San Clemente, CA) employs a unique intercostal implant technique and is designed to function with commercial DF-4 ICD PGs. In this nonrandomized, single-center, acute study, 36 de novo or replacement ICD (transvenous ICD) patients enrolled to receive a concomitant extravascular-ICD lead inserted through an intercostal space along the left parasternal margin. extravascular-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 up or down in 5 to 10 joule increments depending on the success and limitations of the generator used. RESULTS: Successful 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). Furthermore, 24 of 27 (89%) of patients tested with a left, mid-axillary intermuscular PG had successful VF conversion with defibrillation energies at least 10 J below the maximum delivered output of the device. All evaluable episodes (n=93) were automatically sensed, detected, and shocked. No serious device-related intraoperative adverse events were observed. CONCLUSIONS: This first-in-human study documented the safe and reliable placement of a novel extravascular ICD lead with effective sensing and defibrillation of induced ventricular fibrillation using commercial DF-4 ICD PGs.

Impact of Age on Subcutaneous Implantable Cardioverter-Defibrillator in a Large Patient Cohort: Mid-Term Follow-Up.

BACKGROUND: The subcutaneous implantable cardioverter-defibrillator (S-ICD) is an accepted alternative to transvenous (TV) ICD to provide defibrillation therapy to treat life-threatening ventricular tachyarrhythmias in high-risk patients. S-ICD outcomes by age group have not been reported. OBJECTIVES: In this study, the authors sought to report S-ICD outcomes in different age groups in a multicenter S-ICD post-approval study (PAS) involving the largest cohort of patients ever reported. METHODS: Patients were prospectively enrolled in the S-ICD PAS and stratified based on age: young, aged 15-34 years; adult, aged 35-69 years; and elderly, aged ≥70 years. Patient characteristics and clinical outcomes through 3 years of follow up after implantation were compared. RESULTS: The S-ICD PAS enrolled 1,637 patients. Elderly patients were more likely to receive an S-ICD as a replacement of a TV-ICD (15.1% elderly vs 12.3% adult vs 7.4% young). Secondary prevention indication decreased with age (32.7% young vs 22.2% adult vs 20.5% elderly). Mortality rate was significantly higher in the elderly group (24.0% elderly vs 13.0% adult vs 7.4% young; P < 0.0001), whereas the complication rate did not differ significantly (12.3% young vs 11.3% adult vs 8.1% elderly). Rates of appropriate shock (12.7% young vs 13.0% adult vs 13.8% elderly) and inappropriate shock (7.8% young vs 9.1% adult vs 8.8% elderly) rates did not differ between groups (P = 0.96 and P = 0.98, respectively). CONCLUSIONS: Implant complications and appropriate and inappropriate shock rates were similar among age groups. S-ICD for secondary prevention was more common in the young group. Replacing a TV-ICD for an S-ICD increases with age. (S-ICD System Post-Approval Study; NCT01736618).