BACKGROUNDThe 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. METHODSWe 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. RESULTSA 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). CONCLUSIONSIn patients with an indication for an ICD but no indication for pacing, the subcutaneous ICD was noninferior to the transvenous ICD with respect to devicerelated complications and inappropriate shocks. (Funded by Boston Scientific; PRAETORIAN ClinicalTrials.gov number, NCT01296022.

Background: The PRAETORIAN trial showed non-inferiority of the subcutaneous implantable cardioverter-defibrillator (S-ICD) compared to the transvenous ICD (TV-ICD) with regard to inappropriate shocks and complications. In contrast to the TV-ICD, the S-ICD cannot provide antitachycardia pacing (ATP) for monomorphic ventricular tachycardia (VT). This pre-specified secondary analysis evaluates appropriate therapy and whether ATP reduces the number of appropriate shocks. Methods: The PRAETORIAN trial was an international, investigator-initiated randomized trial, which included patients with an indication for ICD therapy. Patients with prior VTs below 170 bpm or refractory recurrent monomorphic VTs 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, 86/426 patients received appropriate therapy, versus 78/423 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 one 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 to 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 ATP attempt successfully terminated 46% of all monomorphic VTs, but accelerated the arrhythmia in 9.4%. Ten S-ICD patients experienced 13 electrical storms, versus 18 TV-ICD patients with 19 electrical storms. Patients with appropriate therapy had an almost two-fold increased relative risk of electrical storms in the TV-ICD group compared to the S-ICD group (P=0.05). Conclusions: In this trial, no difference was observed in shock efficacy of the S-ICD compared with the 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 two groups.

Background: Deep learning (DL) has shown promising results in improving atrial fibrillation (AF) detection algorithms. However, these models are often criticized because of their "black box" nature. Aim: To develop a morphology based DL model to discriminate AF from sinus rhythm (SR), and to visualize which parts of the ECG are used by the model to derive to the right classification. Methods: We pre-processed raw data of 1469 ECGs in AF or SR, of patients with a history AF. Input data was generated by normalizing all single cycles (SC) of one ECG lead to SC-ECG samples by 1) centralizing the R wave or 2) scaling from R-to-R wave. Different DL models were trained by splitting the data in a training, validation and test set. By using a DL based heat mapping technique we visualized those areas of the ECG used by the classifier to come to the correct classification.Results: The DL model with the best performance was a feedforward neural network trained by SC-ECG samples on a R-to-R wave basis of lead II, resulting in an accuracy of 0.96 and F1-score of 0.94. The onset of the QRS complex proved to be the most relevant area for the model to discriminate AF from SR. Conclusion:The morphology based DL model developed in this study was able to discriminate AF from SR with a very high accuracy. DL model visualization may help clinicians gain insights into which (unrecognized) ECG features are most sensitive to discriminate AF from SR.

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/m 2). 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