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.

Successful defibrillation testing in patients undergoing elective subcutaneous implantable cardioverter-defibrillator generator replacement.

AIMS: After implantation of a subcutaneous implantable cardioverter-defibrillator (S-ICD), a defibrillation test (DFT) is performed to ensure that the device can effectively detect and terminate the induced ventricular arrhythmia. Data on DFT efficacy at generator replacement are scarce with a limited number of patients and conflicting results. This study evaluates conversion efficacy during DFT at elective S-ICD generator replacement in a large cohort from our tertiary centre. METHODS AND RESULTS: Retrospective data of patients who underwent an S-ICD generator replacement for battery depletion with subsequent DFT between February 2015 and June 2022 were collected. Defibrillation test data were collected from both implant and replacement procedures. PRAETORIAN scores at implant were calculated. Defibrillation test was defined unsuccessful when two conversions at 65 J failed. A total of 121 patients were included. The defibrillation test was successful in 95% after the first and 98% after two consecutive tests. This was comparable with success rates at implant, despite a significant rise in shock impedance (73 ± 23 vs. 83 ± 24 Ω, P < 0.001). Both patients with an unsuccessful DFT at 65 J successfully converted with 80 J. CONCLUSION: This study shows a high DFT conversion rate at elective S-ICD generator replacement, which is comparable to conversion rates at implant, despite a rise in shock impedance. Evaluating device position before generator replacement may be recommended to optimize defibrillation success at generator replacement.

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.

Long-term performance of a novel communicating antitachycardia pacing-enabled leadless pacemaker and subcutaneous implantable cardioverter-defibrillator system: A comprehensive preclinical study.

BACKGROUND: Subcutaneous implantable cardioverter-defibrillators (S-ICDs) and leadless pacemakers (LPs) are intended to diminish transvenous lead-related complications. However, S-ICDs do not deliver antibradycardia pacing or antitachycardia pacing, and currently, there is no commercially available coordinated leadless option for patients with defibrillator and (expected) pacing needs. OBJECTIVE: We evaluated the performance, safety, and potential replacement strategies of a novel modular cardiac rhythm management (mCRM) system, a wirelessly communicating antitachycardia pacing-enabled LP and S-ICD in a preclinical model. METHODS: LP implantation was attempted in 68 canine subjects, and in 38 an S-ICD was implanted as well. Animals were evaluated serially up to 18 months. At all evaluations, communication thresholds (CTs) between the devices, LP electrical parameters, and system-related complications were assessed. Different replacement strategies were tested. RESULTS: The LP was successfully implanted in 67 of 68 (98.5%) and the concomitant S-ICD in 38 of 38 (100%). mCRM communication was successful in 1022 of 1024 evaluations (99.8%). The mean CT was 2.2 ± 0.7 V at implantation and stable afterward (18 months: 1.8 ± 0.7 V). In multivariable analysis, larger LP-to-S-ICD angle and dorsal posture were associated with higher CTs. At implantation, the mean pacing capture threshold, impedance, and R-wave amplitude were 0.3 ± 0.1 V, 898.4 ± 198.9 Ω, and 26.4 ± 8.2 mV. The mean pacing capture threshold remained stable and impedance and R-wave amplitudes were within acceptable ranges throughout (0.7 ± 0.4 V, 619.1 ± 90.6 Ω, and 20.1 ± 8.4 mV at 18 months). Different replacement strategies seem feasible. CONCLUSION: This first mCRM system demonstrated excellent performance up to 18 months in a preclinical model.

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.

Complications related to elective generator replacement of the subcutaneous implantable defibrillator.

AIMS: To guarantee uninterrupted function of the subcutaneous implantable cardioverter-defibrillator (S-ICD), the pulse generator needs to be surgically replaced before the battery is depleted. The risks related to this replacement substantially impact long-term outcome for S-ICD recipients, as the majority will undergo one or several of these procedures in their lifetime. We aim to describe the procedural characteristics of the replacement procedure and to provide an insight in the complications associated with these replacements. METHODS AND RESULTS: In this retrospective analysis, data from replacement procedures and follow-up visits were collected from all patients who underwent elective S-ICD generator replacement in our tertiary centre from June 2014 until November 2019. Original device position was assessed using the PRAETORIAN score. Complications were defined as those requiring surgical intervention, systemic antibiotic treatment, or device extraction. Seventy-two patients were included, with a median follow-up of 1.9 years (IQR 0.6-3.3 years) after replacement. Battery depletion occurred after 5.9 ± 0.7 years. The pulse generator was repositioned in patients with a PRAETORIAN score ≥90 to minimize the defibrillation threshold. Although there was an increase in impedance compared to the implant procedure, first shock conversion rate during defibrillation testing was 91.4% with a success rate of 100% after multiple attempts. Two patients developed a complication after, respectively, 9 and 21 months, resulting in a complication rate of 1.4% per year. CONCLUSION: With a median follow-up of 1.9 years, this study shows a low complication rate after S-ICD replacement, with a first shock conversion rate of 91.4%.

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.).

Long-term follow-up of the two-incision implantation technique for the subcutaneous implantable cardioverter-defibrillator.

INTRODUCTION: The two-incision implantation technique of the subcutaneous implantable cardioverter-defibrillator (S-ICD) was introduced as an alternative to the standard three-incision approach by omitting the superior parasternal incision. Thereby, complications may be prevented. Short-term follow-up demonstrated the safety and efficacy of the two-incision technique. However, long-term results are lacking. METHODS: This retrospective study included patients implanted between February 2009 and June 2020. Patients were divided into a group of patients who were implanted with the standard three-incision technique and a group who were implanted with the two-incision technique. Outcomes were defibrillation impedance and efficacy and complications requiring intervention. RESULTS: A total of 268 patients were included (age 42.4 ± 16.6 years, 35.4% female, BMI 25.1 ± 4.5 kg/m2 ). Thirty-one patients underwent S-ICD implantation with the three-incision technique and 237 patients with the two-incision technique. First shock efficacy during defibrillation testing was 93% in the three-incision group versus 94% in the two-incision group (P = .69), and shock impedance was 85 versus 68 ohms (P = .04). First shock success was 75% versus 76% for spontaneous episodes (P = 1.00). Complication-free survival at 5-year follow-up in the three-incision group was estimated at 0.96 (95% CI 0.90-1.00) versus 0.98 (95% CI 0.96-1.00) in the two-incision group (P = .20) and for inappropriate shocks at 5-year 0.77 (95% CI 0.63-0.94) versus 0.83 (95% CI 0.77-0.89, P = .30), respectively. CONCLUSION: Five-year follow-up in this S-ICD cohort showed similar complication rates and effectiveness of two-incision technique compared to the three-incision technique. This technique offers physicians a less invasive and more simplified implantation procedure for the S-ICD, with a better cosmetic result.

Improving the care for female subcutaneous ICD patients: A qualitative study of gender-specific issues.

BACKGROUND: The subcutaneous implantable cardioverter-defibrillator (S-ICD) consists of a large generator and is implanted near the left breast. This might lead to discomfort and problems with self-perception and sexuality, especially in the female population. We aimed to assess the issues that female S-ICD patients experience and to provide practical guidance for cardiologists and implanters on minimizing these issues. METHODS: For this retrospective single-center study, we conducted semi-structured interviews with four female S-ICD patients and processed their experiences into a questionnaire. This consisted of three open questions and 17 statements that participants could answer through a five-point Likert scale. The questionnaire was subsequently sent to all female adult patients who received an S-ICD between February 2009 and November 2018 in our tertiary centre in Amsterdam, the Netherlands. RESULTS: The response rate of the questionnaire was 73%, with 52 female respondents (mean age 47.4 ± 12.5 years, mean time since implant 4.6 ± 3.1 years). Postoperative pain exceeded the expectation of 54% of the respondents. Furthermore, 14 out of 49 respondents (29%) expressed an unpleasant feeling during intimate contact with their sexual partner since the implant. Many women (44%) reported daily discomfort caused by their bra and preferred a more cranial and posterior position of the S-ICD generator. Finally, a smaller design of the generator is desired by a great majority (63%) of female S-ICD patients CONCLUSION: Female S-ICD patients experience a variety of issues with a substantial impact on their daily life. Most issues that we identified would benefit from adequate counseling and implanter awareness.

ICD implantation for secondary prevention in patients with ventricular arrhythmia in the setting of acute cardiac ischemia and a history of myocardial infarction.

INTRODUCTION: In patients with a prior myocardial infarction (MI) but preserved left ventricular (LV) function, sustained ventricular arrhythmias (VAs) may arise in the setting of an acute coronary syndrome (ACS). It is unknown whether an implantable cardioverter-defibrillator (ICD) is mandatory in these patients as VA might be triggered by a reversible cause. The purpose of this study is to analyze the benefit of ICD therapy in this patient population. METHODS: We conducted a retrospective observational study in ICD recipients implanted from 2008 to 2011. The study group consisted of patients with sustained VA in the setting of an ACS, with a history of MI, but with left ventricular ejection fraction (LVEF) greater than 35 (group A). The two control groups consisted of patients admitted with VA with a history of MI, but without ACS at presentation, either with LVEF greater than 35% (group B) or ≤35% (group C). The primary endpoint was the number of patients with appropriate ICD therapy (antitachycardia pacing or shock). RESULTS: A total of 291 patients were included with a mean follow-up of 5.3 years. Appropriate ICD therapy occurred in 45.6% of the patients in group A vs 51.6% and 60.4% in groups B and C (P = .11). In group A, 31.1% received an appropriate ICD shock vs 34.7% and 44.3% in control groups B and C (P = .12). CONCLUSION: On the basis of these data, ICD implantation seems warranted in patients with history of MI presenting with VA in the setting of an ACS, despite preserved LV function and adequate revascularization. Further trials, preferably randomizes, should be performed to address these findings.

Leadless cardiac pacing systems: current status and future prospects.

Introduction: Permanent transvenous pacemaker therapy is an essential management option in patients with symptomatic bradyarrhythmias, but harbors a concomitant risk of serious complications. As most complications are lead- or pocket-related, intracardiac leadless pacemaker therapy has the potential to positively impact patient outcome. Since the first leadless pacemaker implant in 2012, many studies have been conducted to evaluate the effectiveness, safety, and applicability of this novel pacing approach.Areas covered: This review will cover the current status of leadless pacemaker technology. Available safety and efficacy outcomes, current area of indication, and end-of-life management will be evaluated. Furthermore, future perspectives for clinical practice and new pacing modalities are discussed.Expert opinion: The first-generation leadless pacemakers are a promising innovation that provide safe and efficient single-chamber pacing therapy without the use of transvenous pacemaker leads. Yet, broad implementation of this technology is hampered by limitations of the current leadless devices, such as end-of-life management and its single-chamber pacing indication. Further innovations such as leadless dual-chamber pacing therapy, leadless cardiac synchronization therapy, energy-harvesting leadless pacemakers, communicating leadless pacemakers with subcutaneous implantable cardiac defibrillators, and minimally invasive completely extracardiac pacemakers are currently being developed that have the potential to become major game changers in pacing therapy.

Minimal defibrillation thresholds and the correlation with implant position in subcutaneous implantable-defibrillator patients.

BACKGROUND: Since the introduction of the subcutaneous implantable-defibrillator (S-ICD) knowledge of factors elevating the defibrillation threshold (DFT), have increased. Optimal device positioning most likely results in a decrease in DFT. The PRAETORIAN score is a tool to systematically evaluate S-ICD implant position and predict conversion success by estimating the DFT on a chest X-ray. The objective of this study is to determine DFT in de novo S-ICD patients. METHODS: De novo S-ICD patients were enrolled with DFT testing using a single 30 J shock or a prespecified step-down protocol. Chest X-rays were obtained and implant position was evaluated using the PRAETORIAN score. RESULTS: Fifteen patients, age 47 (±18) years and body mass index (BMI) 25(±3) kg/m2 , underwent conversion testing with a single 30 J shock. Fourteen patients (93%) converted successfully. Implant position was optimal in all patients, PRAETORIAN score of 30 (100%). Twelve patients were available for analysis in the step-down DFT cohort, age 46 years (±15), left ventricular ejection fraction 50% (±15%) and a median BMI of 25.7 kg/m2 (range 23.8-29.1 kg/m2 ). No complications occurred during DFT testing. Mean DFT was 29 J (±12 J). Time to shock was 11 seconds (±2 seconds) for a 20 J shock compared with 17 seconds in case of a 70 J shock output. Nearly all patients were implanted with optimal device positioning with the lowest possible PRAETORIAN score of 30 (92%). CONCLUSION: DFT in S-ICD patients with optimal device positioning is lower than previously reported. Conversion testing using a low shock output reduced time to therapy by 6 seconds on average.

Feasibility of An Entirely Extracardiac, Minimally Invasive,Temporary Pacing System.

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.

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.

A novel tool to evaluate the implant position and predict defibrillation success of the subcutaneous implantable cardioverter-defibrillator: The PRAETORIAN score.

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-<90 points representing a low risk, 90-<150 points representing an intermediate risk, and ≥150 points representing a high risk of conversion failure. The score was developed using 2 separate S-ICD data sets for derivation and validation. The performance metrics are the positive and negative predictive values. RESULTS: The development data set consisted of 181 patients with S-ICD, and the validation cohort consisted of 321 patients from the S-ICD Investigational Device Exemption trial. The distribution of scores was 93%-98% low risk (<90 points), 2%-5% intermediate risk (90-<150 points), and 1% high risk (≥150 points). The positive predictive value for an intermediate or high PRAETORIAN score for a failed conversion test was 51%, while a low PRAETORIAN score predicted a successful conversion in 99.8% of patients. CONCLUSION: The PRAETORIAN score allows the identification of patients with high defibrillation thresholds by using the routine chest radiograph and provides feedback to implanters on S-ICD positioning. The PRAETORIAN-DFT trial will prospectively validate the score by randomizing to standard conversion testing vs using the score without conversion testing.

Clinical parameters to optimize patient selection for subcutaneous and transvenous implantable defibrillator therapy.

BACKGROUND: The subcutaneous implantable cardioverter-defibrillator (S-ICD) lacks the antitachycardia pacing (ATP) capability of tranvenous ICDs (TV-ICD). S-ICD patient selection can be challenging as some patients may benefit from ATP. We aim to identify clinical predictors of ATP benefit, in order to improve patient selection for S-ICD or TV-ICD therapy. METHODS: De novo single- and dual-chamber TV-ICD patients implanted between March 2011 and December 2015 were included. Ventricular arrhythmias terminated by ATP and not followed by a shock were considered successful ATP therapy. Cox proportional hazard analysis was performed to assess the adjusted effect of multiple predictors for appropriate ATP and shock therapy. RESULTS: Note that 431 patients were included with a median follow-up of 26 months. Ninety-nine patients (23%) received appropriate ATP therapy, which terminated the arrhythmia in 67%. A history of nonsustained ventricular tachycardia (NSVT) or monomorphic VT (MVT) was the only predictor of appropriate ATP therapy in the multivariable model (hazard ratio [HR] 2.73, P < 0.001). Sixty-five of 221 patients with a history of NS (VT) received appropriate ATP (29%) versus 24 patients (11%) without a history NS (VT) (P < 0.001). A secondary prevention indication was the only predictor in the multivariate model for appropriate shock therapy (HR 1.82, P  =  0.05). CONCLUSION: A history of NSVT or MVT is a significant predictor for appropriate and successful ATP therapy. One in three patients with NSVT or MVT received appropriate ATP versus one in 10 patients without a history of NSVT or MVT over a 2-year period of follow-up.

Six-year follow-up of the initial Dutch subcutaneous implantable cardioverter-defibrillator cohort: Long-term complications, replacements, and battery longevity.

INTRODUCTION: Experience with the subcutaneous implantable cardioverter-defibrillator (S-ICD) is expanding rapidly. However, data on long-term performance or complications related to elective generator replacement are lacking. METHODS: Follow-up (FU) data of all patients implanted between December 2008 and April 2011 were collected. Complications were defined as those requiring surgical intervention. Kaplan-Meier estimates for complication and shock rates, with corresponding 95% confidence intervals (CI), were calculated. RESULTS: One hundred and eighteen patients were included. Median FU was 6.1 years (IQR 5.6-6.5 years). Short-term complication rate (0-30 days) was 3% (CI 0-6%). Long-term complication rate at 6 years was 19% (CI 12-26%), corresponding with an annual complication rate of 3%. One patient in this cohort developed a need for a transvenous ICD (TV-ICD) in order to provide pacing for bradycardia (1%). Six patients were implanted with a TV-ICD after experiencing an S-ICD complication for which extraction was necessary. In total, 10 S-ICDs were extracted; none resulted in a complication. Eight patients had a nonsystemic ICD-related infection and no lead failures were observed. The majority, 68 (58%) patients, received an elective generator replacement. Two patients had a complication related to generator replacement (3%). Battery longevity was 5.6 years (IQR 5.2-6.1). Appropriate and inappropriate shock rates of 6-year estimates were 17% (CI 9-25%) and 21% (CI 15-27%), respectively. CONCLUSIONS: This cohort represents the longest follow-up to date and shows a low annual complication rate without lead failures or systemic infections. Battery longevity of the first S-ICD generation results in relative early generator replacement procedures.

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.