Is it safe to give birth with an activated implantable cardioverter-defibrillator: A multicentre observational study.

OBJECTIVE: Data and guidelines are lacking, so implantable cardioverter-defibrillators (ICDs) are often deactivated during labour to prevent inappropriate shocks. This study aimed to ascertain the safety of an activated ICD during labour. DESIGN: An observational study was performed. SETTING: Dutch hospitals. POPULATION OR SAMPLE: A total of 41 childbirths were included of 26 patients who gave birth between February 2009 and November 2018 after receiving an ICD in our tertiary hospital. Five of these childbirths were attended by the research team between December 2018 and August 2020, during which the ICD remained active. METHODS: Groups were made based on ICD status during labour. Patients who gave birth with an activated ICD at least once were stratified to the activated ICD group. Patients' files were checked and patients received a questionnaire about childbirth perceptions and treatment preferences. The differences in ordinal data resulting from the questionnaire were calculated using a chi-square or Fisher's exact test. MAIN OUTCOME MEASURES: Primary outcome was inappropriate ICD therapy and occurrence of ventricular arrhythmias requiring treatment. RESULTS: During the 41 childbirths, no inappropriate shocks or ventricular arrhythmias occurred during labour. All patients in the activated ICD group (n = 13) preferred this setting, while 8 of the 13 patients in the deactivated ICD group preferred activation (p = 0.002). Reasons included avoiding hemodynamic monitoring, magnet placement, or labour induction to facilitate technician availability. CONCLUSIONS: This study shows no evidence that labour and birth in women with an activated ICD are unsafe, as there were no ventricular arrhythmias or inappropriate therapy. In addition, most patients prefer an activated ICD during labour.

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.).

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.

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.

Which patients are not suitable for a subcutaneous ICD: incidence and predictors of failed QRS-T-wave morphology screening.

BACKGROUND: The subcutaneous cardioverter-defibrillator (S-ICD) relies on a pre-implantation QRS-T morphology screening (TMS) of the ECG to assure that it reliably detects the QRS complexes and T waves. The prevalence and clinical characteristics of the patients who fail this TMS is unknown. METHODS AND RESULTS: QRS-TMS was done in 230 consecutive ICD outpatients (75% male, age 57 ± 15 years) without an indication for cardiac pacing, using an ECG simulating the 3 sensing vectors of the S-ICD (TMS-ECG). Patients were defined suitable when at least 1 sensing vector was considered appropriate in both supine and standing position. In total, 7.4% of patients, who were all male, were considered not suitable for a S-ICD according to the TMS-ECG. Independent predictors for TMS failure were hypertrophic cardiomyopathy (HCM; odds ratio [OR] 12.6), a heavy weight (OR 1.5), a prolonged QRS duration (OR 1.5) and a R:T ratio <3 in the lead with the largest T wave on a standard 12-lead surface ECG (OR 14.6). CONCLUSION: In patients without an indication for pacing, 7.4% would have been not suitable for a S-ICD according to the TMS. HCM, a heavy weight, a prolonged QRS duration and a R:T ratio <3 in the ECG lead with the largest T wave were independently associated with TMS failure. These data might alert physicians that selection of patients for a S-ICD should be considered with special caution in certain patient groups, because they may not satisfy ECG criteria for adequate sensing.

Fifteen years of subcutaneous implantable cardioverter-defibrillator therapy: Where do we stand, and what will the future hold?

The subcutaneous implantable cardioverter-defibrillator (S-ICD) has emerged as a feasible alternative for the transvenous ICD in the treatment of ventricular tachyarrhythmias in patients without pacing or cardiac resynchronization therapy indications. Since its introduction, numerous innovations have been made and clinical experience was gained leading to its adoption in current practice and preference in certain populations. Moreover, emerging technologies like the extravascular ICD or the combination of the S-ICD with the leadless pacemaker offer new possibilities for the future. These advancements underscore the S-ICD's evolving role in ventricular tachyarrhythmia management. This review outlines implantation considerations, patient selection and troubleshooting advancements in the last 15 years and also provides insights into future perspectives.

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.

Rationale and design of the PRAETORIAN trial: a Prospective, RAndomizEd comparison of subcuTaneOus and tRansvenous ImplANtable cardioverter-defibrillator therapy.

BACKGROUND: Implantable cardioverter-defibrillators (ICDs) are widely used to prevent fatal outcomes associated with life-threatening arrhythmic episodes in a variety of cardiac diseases. These ICDs rely on transvenous leads for cardiac sensing and defibrillation. A new entirely subcutaneous ICD overcomes problems associated with transvenous leads. However, the role of the subcutaneous ICD as an adjunctive or primary therapy in patients at risk for sudden cardiac death is unclear. STUDY DESIGN: The PRAETORIAN trial is an investigator-initiated, randomized, controlled, multicenter, prospective 2-arm trial that outlines the advantages and disadvantages of the subcutaneous ICD. Patients with a class I or IIa indication for ICD therapy without an indication for bradypacing or tachypacing are included. A total of 700 patients are randomized to either the subcutaneous or transvenous ICD (1:1). The study is powered to claim noninferiority of the subcutaneous ICD with respect to the composite primary endpoint of inappropriate shocks and ICD-related complications. After noninferiority is established, statistical analysis is done for potential superiority. Secondary endpoint comparisons of shock efficacy and patient mortality are also made. CONCLUSION: The PRAETORIAN trial is a randomized trial that aims to gain scientific evidence for the use of the subcutaneous ICD compared with the transvenous ICD in a population of patients with conventional ICD with respect to major ICD-related adverse events. This trial is registered at ClinicalTrials.gov with trial ID NCT01296022.

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.

Genetic aspects of vasovagal syncope: a systematic review of current evidence.

Knowledge on the aetiology of vasovagal syncope (VVS) is of great importance to optimize its diagnostic and therapeutic options. To unravel the largely unknown pathophysiology, studies on genetic aspects of VVS can be of use. This systematic review on all available literature aims to provide an overview of the current knowledge of VVS genetics. The MEDLINE and EMBASE database were systematically searched for all studies discussing genetic factors as a cause of VVS. Hereditary aspects of VVS were studied in 19 studies. Six studies determined a positive family history in, respectively, 19-90% of the VVS patients. These numbers, however, are not higher than the cumulative incidence of VVS in the general population (35-39%). Four studies examined potential genetic polymorphisms associated with VVS. Only a Gly389 allele was more frequently present in VVS patients with a positive HUT test, although the significance level was set much higher than usual in genetic studies, and this result has not been replicated so far. Knowledge on genetic aspects of VVS could be very useful in clinical practice and research, but the current evidence that it has a genetic basis is not very strong.

Syncope prevalence in the ED compared to general practice and population: a strong selection process.

OBJECTIVE: We assessed the prevalence and distribution of the different causes of transient loss of consciousness (TLOC) in the emergency department (ED) and chest pain unit (CPU) and estimated the proportion of persons with syncope in the general population who seek medical attention from either their general practitioner or the ED/CPU. METHODS: A review of the charts of consecutive patients presenting with TLOC at the ED/CPU of our university hospital between 2000 and 2002 was conducted. Patients younger than 12 years or with a known epileptic disorder were excluded. Age and sex of syncopal patients were compared with those in a general practice and general population data sets. MAIN FINDINGS AND CONCLUSIONS: During the study period, 0.94% of the patients visiting the ED/CPU presented with TLOC (n = 672), of which half had syncope. Only a small but probably selected group of all people with syncope visit the ED/CPU.

Algorithm-Based Screening May Improve Patient Selection for the Subcutaneous Implantable Defibrillator.

OBJECTIVES: The study sought to describe the concept of algorithm-based screening with an external subcutaneous implantable cardioverter-defibrillator (S-ICD) to evaluate sensing using the rhythm discrimination algorithm of the device. BACKGROUND: In a proportion of patients, screening for S-ICD therapy with the dedicated screening tool results in false negative and false positive results. METHODS: Both patients who failed the standard screening and who passed with abnormal baseline ECGs were screened with an external S-ICD to evaluate sensing at rest and during exercise in all 3 sensing vectors (algorithm-based screening). Patients with adequate sensing were implanted with an S-ICD. Follow-up data regarding (in)appropriate shocks was collected. RESULTS: Algorithm-based screening was performed in 15 patients. Group 1 consists of 8 who failed standard screening and Group 2 consists of 7 who passed and had abnormal ECGs. Six of 8 who failed standard screening in all sensing vectors demonstrated adequate sensing with the external S-ICD and were implanted with an S-ICD. Of these 6 implanted patients in Group 1, 1 inappropriate shock was observed duration median of 17 months' follow-up and 2 episodes of ventricular fibrillation were successfully treated. Of the 7 patients in Group 2, who passed standard screening, 2 demonstrated inadequate sensing during additional screening with the external S-ICD. No appropriate or inappropriate shocks were observed in Group 2 during 10 months' follow-up. CONCLUSIONS: Algorithm-based screening with the external S-ICD may improve patient selection and reduce the number of false positive and false negative screening results of the standard screening method.

Implantable cardioverter-defibrillator harm in young patients with inherited arrhythmia syndromes: A systematic review and meta-analysis of inappropriate shocks and complications.

BACKGROUND: Implantable cardioverter-defibrillators (ICDs) are implanted with the intention to prolong life in selected patients with inherited arrhythmia syndromes, but ICD implantation is also associated with inappropriate shocks and complications. OBJECTIVE: We aimed to quantify the rate of inappropriate shocks and other ICD-related complications to be able to weigh benefit and harm in these patients. METHODS: We performed a systematic review and meta-analysis of inappropriate shock and/or other ICD-related complication rates, including ICD-related mortality, in patients with inherited arrhythmia syndromes, that is, arrhythmogenic right ventricular cardiomyopathy/dysplasia, Brugada syndrome, catecholaminergic polymorphic ventricular tachycardia, hypertrophic cardiomyopathy, dilated cardiomyopathy due to a mutation in the lamin A/C gene, long QT syndrome, and short QT syndrome. We searched MEDLINE and EMBASE from inception to May 30, 2014. RESULTS: Of 2471 unique citations, 63 studies comprising 4916 patients with inherited arrhythmia syndromes (mean age of 39 ± 15 years) were included. Inappropriate shocks occurred in 20% of patients (crude annual rate of 4.7% per year), with a significantly higher rate in studies published before 2008 (6.1% per year vs 4.1% per year). Moreover, 22% experienced ICD-related complications (4.4% per year) and there was a 0.5% ICD-related mortality (0.08% per year). CONCLUSION: ICD implantation carries a significant risk of inappropriate shocks and inhospital and postdischarge complications in relatively young patients with inherited arrhythmia syndromes. These data can be used to better inform patients and physicians about the expected risk of adverse ICD events and thereby facilitate shared decision making.

Prevalence of subcutaneous implantable cardioverter-defibrillator candidacy based on template ECG screening in patients with hypertrophic cardiomyopathy.

BACKGROUND: Subcutaneous implantable cardioverter-defibrillator (S-ICD) is a promising option for patients with hypertrophic cardiomyopathy (HCM). Patients with HCM can present markedly abnormal electrocardiograms (ECGs), and there are no data on what percentage of patients with HCM fail the prerequisite S-ICD vector screening. OBJECTIVE: The purpose of this study was to determine the failure rate of the prerequisite vector screening using 1 or 2 acceptable vectors stratified for risk profile for sudden cardiac death and predictors of failure. METHODS: ECG recordings from consecutive patients with HCM simulating the S-ICD sensing vectors were analyzed with the S-ICD screening tool. Eligibility was defined by 1 or 2 appropriate vectors. Medical history, ultrasound characteristics, and 12-lead ECG characteristics were analyzed and the individual arrhythmic risk at 5 year was determined to study potential predictors of failure. RESULTS: One hundred sixty-five (118 men; mean age 51 ± 16 years) patients were analyzed. Twenty-two patients (13%) had a high risk of sudden cardiac death, 33 (20%) had intermediate to high risk, and 110 (67%) had low risk. Twenty-six patients (16%) had no suitable vector, including 8 of 22 high-risk patients (36%). The primary cause of failure was high T-wave voltages in 25% of the vectors analyzed. T-wave inversions in >2 leads on the surface 12-lead ECG (odds ratio 15.6; 95% confidence interval 4.9-50.3; P < .001) and prior myectomy (odds ratio 8.4; 95% confidence interval 2.1-33.1; P = .002) were significantly associated with screening failure in a multivariable model. CONCLUSION: Currently available preimplant screening algorithms recommended by the manufacturer are associated with a significant failure rate in patients with HCM, particularly in the high-risk subgroup.

Surgical Management of Implantation-Related Complications of the Subcutaneous Implantable Cardioverter-Defibrillator.

OBJECTIVES: This study assessed outcomes in patients in whom subcutaneous implantable cardioverter-defibrillator (S-ICD) therapy was continued after implantation-related complications, in order to avoid conversion to transvenous ICD therapy. BACKGROUND: Patients at risk for sudden cardiac death benefit from ICD therapy, despite a significant risk for complications. S-ICD has a similar complication rate as transvenous ICD therapy, but the absence of transvenous leads may hold long-term benefits, especially in young ICD patients. METHODS: In the largest single-center cohort available to date, S-ICD patients implanted between 2009 and 2015 were included. RESULTS: There were 123 patients at a median age of 40 years. During a median follow-up of 2 years, 10 patients (9.4%) suffered implant-related complications. There were 5 infections, 3 erosions, and 2 implant failures for which 21 surgical procedures were needed. In 9 of 10 patients, S-ICD therapy could be continued after intervention. In 6 patients, the period between extraction and reimplantation of the S-ICD system was bridged with a wearable cardioverter-defibrillator (WCD). The pulse generator was reimplanted at the original site in 5 patients and in 3 underneath the serratus anterior muscle. One patient was not reimplanted following extraction due to recurrent infections. Conversion to a transvenous ICD was not needed in any patient. CONCLUSIONS: In most patients with a complication, S-ICD therapy could be continued after intervention, avoiding the need to convert to a transvenous system. Bridging to recovery with a WCD and submuscular implantation of the pulse generator are effective treatment strategies to manage S-ICD complications.

Long-Term Clinical Outcomes of Subcutaneous Versus Transvenous Implantable Defibrillator Therapy.

BACKGROUND: Transvenous implantable cardioverter-defibrillators (TV-ICDs) improve survival in patients at risk for sudden cardiac death, but complications remain an important drawback. The subcutaneous ICD (S-ICD) was developed to overcome lead-related complications. Comparison of clinical outcomes of both device types in previous studies was hampered by dissimilar patient characteristics. OBJECTIVES: This retrospective study compares long-term clinical outcomes of S-ICD and TV-ICD therapy in a propensity-matched cohort. METHODS: The authors analyzed 1,160 patients who underwent S-ICD or TV-ICD implantation in 2 high-volume hospitals in the Netherlands. Propensity matching for 16 baseline characteristics, including diagnosis, yielded 140 matched pairs. Clinical outcomes were device-related complications requiring surgical intervention, appropriate and inappropriate ICD therapy, and were reported as 5-year Kaplan-Meier rate estimates. RESULTS: All 16 baseline characteristics were balanced in the matched cohort of 140 patients with S-ICDs and 140 patients with TV-ICDs (median age 41 years [interquartile range: 30 to 52 years] and 40% women). The complication rate was 13.7% in the S-ICD group versus 18.0% in the TV-ICD group (p = 0.80). The infection rate was 4.1% versus 3.6% in the TV-ICD groups (p = 0.36). Lead complications were lower in the S-ICD arm compared with the TV-ICD arm, 0.8% versus 11.5%, respectively (p = 0.03). S-ICD patients had more nonlead-related complications than TV-ICD patients, 9.9% versus 2.2%, respectively (p = 0.047). Appropriate ICD intervention (antitachycardia pacing and shocks) occurred more often in the TV-ICD group (hazard ratio [HR]: 2.42; p = 0.01). The incidence of appropriate (TV-ICD HR: 1.46; p = 0.36) and inappropriate shocks (TV-ICD HR: 0.85; p = 0.64) was similar. CONCLUSIONS: The complication rate in patients implanted with an S-ICD or TV-ICD was similar, but their nature differed. The S-ICD reduced lead-related complications significantly, at the cost of nonlead-related complications. Rates of appropriate and inappropriate shocks were similar between the 2 groups.