Terminating spiral waves with a single designed stimulus: Teleportation as the mechanism for defibrillation.

We identify and demonstrate a universal mechanism for terminating spiral waves in excitable media using an established topological framework. This mechanism dictates whether high- or low-energy defibrillation shocks succeed or fail. Furthermore, this mechanism allows for the design of a single minimal stimulus capable of defibrillating, at any time, turbulent states driven by multiple spiral waves. We demonstrate this method in a variety of computational models of cardiac tissue ranging from simple to detailed human models. The theory described here shows how this mechanism underlies all successful defibrillation and can be used to further develop existing and future low-energy defibrillation strategies.

Prediction of Shock-Refractory Ventricular Fibrillation During Resuscitation of Out-of-Hospital Cardiac Arrest.

BACKGROUND: Out-of-hospital cardiac arrest due to shock-refractory ventricular fibrillation (VF) is associated with relatively poor survival. The ability to predict refractory VF (requiring ≥3 shocks) in advance of repeated shock failure could enable preemptive targeted interventions aimed at improving outcome, such as earlier administration of antiarrhythmics, reconsideration of epinephrine use or dosage, changes in shock delivery strategy, or expedited invasive treatments. METHODS: We conducted a cohort study of VF out-of-hospital cardiac arrest to develop an ECG-based algorithm to predict patients with refractory VF. Patients with available defibrillator recordings were randomized 80%/20% into training/test groups. A random forest classifier applied to 3-s ECG segments immediately before and 1 minute after the initial shock during cardiopulmonary resuscitation was used to predict the need for ≥3 shocks based on singular value decompositions of ECG wavelet transforms. Performance was quantified by area under the receiver operating characteristic curve. RESULTS: Of 1376 patients with VF out-of-hospital cardiac arrest, 311 (23%) were female, 864 (63%) experienced refractory VF, and 591 (43%) achieved functional neurological survival. Total shock count was associated with decreasing likelihood of functional neurological survival, with a relative risk of 0.95 (95% CI, 0.93-0.97) for each successive shock (P<0.001). In the 275 test patients, the area under the receiver operating characteristic curve for predicting refractory VF was 0.85 (95% CI, 0.79-0.89), with specificity of 91%, sensitivity of 63%, and a positive likelihood ratio of 6.7. CONCLUSIONS: A machine learning algorithm using ECGs surrounding the initial shock predicts patients likely to experience refractory VF, and could enable rescuers to preemptively target interventions to potentially improve resuscitation outcome.

A comprehensive protocol combining in vivo and ex vivo electrophysiological experiments in an arrhythmogenic animal model.

Ventricular arrhythmias contribute significantly to cardiovascular mortality, with coronary artery disease as the predominant underlying cause. Understanding the mechanisms of arrhythmogenesis is essential to identify proarrhythmic factors and develop novel approaches for antiarrhythmic prophylaxis and treatment. Animal models are vital in basic research on cardiac arrhythmias, encompassing molecular, cellular, ex vivo whole heart, and in vivo models. Most studies use either in vivo protocols lacking important information on clinical relevance or exclusively ex vivo protocols, thereby missing the opportunity to explore underlying mechanisms. Consequently, interpretation may be difficult due to dissimilarities in animal models, interventions, and individual properties across animals. Moreover, proarrhythmic effects observed in vivo are often not replicated in corresponding ex vivo preparations during mechanistic studies. We have established a protocol to perform both an in vivo and ex vivo electrophysiological characterization in an arrhythmogenic rat model with heart failure following myocardial infarction. The same animal is followed throughout the experiment. In vivo methods involve intracardiac programmed electrical stimulation and external defibrillation to terminate sustained ventricular arrhythmia. Ex vivo methods conducted on the Langendorff-perfused heart include an electrophysiological study with optical mapping of regional action potentials, conduction velocities, and dispersion of electrophysiological properties. By exploring the retention of the in vivo proarrhythmic phenotype ex vivo, we aim to examine whether the subsequent ex vivo detailed measurements are relevant to in vivo pathological behavior. This protocol can enhance greater understanding of cardiac arrhythmias by providing a standardized, yet adaptable model for evaluating arrhythmogenicity or antiarrhythmic interventions in cardiac diseases.NEW & NOTEWORTHY Rodent models are widely used in arrhythmia research. However, most studies do not standardize clinically relevant in vivo and ex vivo techniques to support their conclusions. Here, we present a comprehensive electrophysiological protocol in an arrhythmogenic rat model, connecting in vivo and ex vivo programmed electrical stimulation with optical mapping. By establishing this protocol, we aim to facilitate the adoption of a standardized model for investigating arrhythmias, enhancing research rigor and comparability in this field.

Preoperative Prediction of Shock Impedance for Subcutaneous Implantable Cardioverter Defibrillator Using Chest Computed Tomography.

BACKGROUND: High shock impedance is associated with conversion failure among patients with subcutaneous implantable cardioverter defibrillators (S-ICD). Currently, there is no preoperative assessment method for predicting high shock impedance. This study examined the efficacy of chest computed tomography (CT) as a preoperative evaluation tool to assess the shock impedance of S-ICDs. METHODS AND RESULTS: The amount of adipose tissue adjacent to the device and anteroposterior diameter at the basal heart region were measured preoperatively using chest CT. We examined the correlation between these measurements and shock impedance at the conversion test. We enrolled 43 patients with S-ICDs (mean [±SD] age 54±15 years; body mass index 23±4 kg/m2; PRAETORIAN score 30-270 points; amount of adipose tissue 1,250±716 cm3), who underwent intraoperative conversion tests by inducing ventricular fibrillation, which was terminated with a 65-J shock. A sufficient concordance correlation coefficient was observed between the shock impedance and the amount of adipose tissue (r=0.616, P<0.01) and anteroposterior diameter (r=0.645, P<0.01). In multiple regression analysis, the amount of adipose tissue (ß=0.439, P=0.009) and anteroposterior diameter (ß=0.344, P=0.038) were identified as independent predictive factors of shock impedance. CONCLUSIONS: The preoperative CT-measured amount of adipose tissue and basal heart anteroposterior diameter are independent predictors of shock impedance. These parameters may be more accurate in identifying higher shock impedance in patients with S-ICDs.

Utility of routine follow-up defibrillation safety margin testing in young patients with epicardial implantable cardioverter-defibrillators.

BACKGROUND: Routine defibrillation threshold testing (DFT) of transvenous implantable defibrillators (ICDs) has largely been in decline. In patients with non-transvenous ICDs that utilize subcutaneous and pleural ICD leads, serial DFT testing can detect a significant number of failures. Data about the utility of follow-up defibrillation safety margin testing (DSM) testing in pediatric patients and young adults with an epicardial ICD are lacking. METHODS: Patients aged < 25 years old who underwent epicardial ICD placement at Mayo Clinic from 2014 to 2023 with at least one follow-up DSM test were included. The patients were divided into a "routine" (R) and "clinically indicated" (CI) group based on the index of clinical concern. Inadequate DSM was defined as unsuccessful defibrillation at an output of less than 10 J below the maximum output of the device. The purpose of this study was to assess the utility of follow-up DSM testing. RESULTS: An epicardial ICD system was placed in 122 patients. A total of 26 patients met inclusion criteria and underwent a total of 47 DSM follow up tests. Inadequate DSM occurred in 1/33 (3%) in the R group and 2/14 (14%) DSM tests in the CI group. The median follow-up period was 54 and 36 months for the R and CI group, respectively. CONCLUSIONS: Our data suggest that epicardial ICDs are reliable and routine follow-up DSM testing may not be necessary for all patients. DSM testing should be performed in individuals with epicardial ICD systems when there is clinical concern about lead or coil performance.

A manual synchronous low energy shock impedance as a predictor of successful defibrillation testing during subcutaneous ICD implantation.

BACKGROUND: Guidelines recommend defibrillation testing (DFT) during subcutaneous implantable cardioverter-defibrillator (S-ICD) implantation. Implant position, patient characteristics and device factors, such as shock impedance, influence defibrillation success. To evaluate the shock impedance, a manual synchronous 10J shock (low energy synchronous shock [LESS]) can be delivered, without the need to induce ventricular fibrillation (VF). OBJECTIVE: To compare LESS and DFT impedance values and to evaluate the diagnostic accuracy of LESS impedance for predicting a successful DFT during S-ICD implantation. METHODS: Consecutive S-ICD implantations were included. Shock impedances were compared by paired t-tests. Univariate analysis was performed to investigate factors associated with successful DFT. A prediction model of successful DFT based on LESS impedance was assessed by logistic regression. Receiver operating characteristic (ROC) curve, area under the ROC curve and the Hosmer-Lemeshow tests were used to evaluate the accuracy of LESS impedance. RESULTS: Sixty patients were included (52 ± 14 years; 69% male). LESS and DFT impedance values were highly correlated (r2 = 0.97, p < .01). Patients with a failed first shock had higher body mass index (BMI) (30 ± 3 vs. 25.7 ± 4.3, p = .014), higher mean LESS (120 ± 35Ω vs. 86. ± 23Ω, p = .0013) and DFT impedance (122 ± 33Ω vs. 87 ± 24Ω, p = .0013). ROC analysis showed that LESS impedance had a good diagnostic performance in predicting a successful conversion test (AUC 84% [95% CI: 0.72-0.92]) with a cutoff value of <94Ω to identify a successful DFT (sensitivity 71%, specificity 73%). CONCLUSION: LESS impedance values without the need to induce VF can intraoperatively predict a successful DFT.

Patients with a high defibrillation threshold: Approaches to management.

Implantable cardioverter-defibrillators (ICDs) have revolutionized the prognosis for patients at elevated risk of ventricular tachyarrhythmias. For safety, defibrillation should be effective with a minimum of 10 J below the device's maximum energy. While modern ICDs rarely deliver ineffective shocks in primary prevention, the surge in managing severe heart failure patients has led to an increased number of patients with high defibrillation thresholds (DFTs). This article elucidates the potential causes of high DFT, including clinical factors, lead and device placement, the presence of a Left Ventricular Assist Device (LVAD), prolonged ventricular arrhythmias, shock vectors, waveform tilt, medications, and manufacturer-specific options. We also detail management strategies, highlighting alternative shock coil placements, practical recommendations, and case studies from our institution. Our management algorithm suggests addressing preventable causes, re-evaluating coil positions, considering non-invasive system modifications, upgrading to a higher-capacity device, and adding extra coil(s).

Optimizing defibrillator deployment with bus-mounted automated external defibrillator.

OBJECTIVES: Early defibrillation with an automated external defibrillator (AED) can effectively improve the survival rate of patients with out-of-hospital cardiac arrest (OHCA). Placing AEDs in public locations can reduce the defibrillation response interval from collapse to defibrillation. Most public AEDs are currently placed in a stationary way (S-AED) with limited coverage area. Bus mounted AED (B-AED) can be delivered directly to the demand point. Although B-AEDs are only available during bus operating hours, they provide greater coverage area. When the number of available AEDs is insufficient, better coverage may be achieved by placing a portion of AEDs as B-AEDs. Our purpose is developing a model to determine the optimal locations of B-AEDs and S-AEDs with a predetermined number of available AEDs. The goal is to maximize the total coverage level of all demand points. METHODS: We proposed a joint location model to place B-AEDs and S-AEDs based on the p-median problem (JPMP). Using data from Chang'an District, Xi'an City, China, we determined the optimal AED deployment. The performance of JPMP was compared with several other models. The coverage results of JPMP are analyzed in details, including the quantity assignment, coverage level, and geographical location of B-AEDs and S-AEDs. The impact of the bus departure intervals on coverage was also discussed. RESULTS: The use of B-AEDs results in an average 98.43% increase in the number of covered demand points, and an average 74.05% increase in total coverage level. In optimal AED deployment, B-AEDs coverage follows an inverted U-shaped curve with increasing number of available AEDs. It begins to decrease when all demand points during the operating hours are covered. With a constant number of available AEDs, the total coverage level increases and then decreases as the bus departure interval increases. The larger the number of available AEDs, the smaller the optimal departure interval. CONCLUSIONS: With a given number of available AEDs, combinational deployment of B-AEDs and S-AEDs significantly improves the coverage level. B-AEDs are recommended when AEDs are insufficient. If more AEDs are available, better coverage can be obtained with reasonable location of S-AEDs and B-AEDs.

Defibrillation strategies for patients with refractory ventricular fibrillation: A systematic review and meta-analysis.

AIM: The aim of this study was to summarize the existing evidence about the effectiveness of double defibrillation (DD) in comparison to standard defibrillation for patients with refractory ventricular fibrillation (RVF). DD encompasses double "sequential" external defibrillation (DSeq-D) and double "simultaneous" defibrillation (DSim-D), with the study also shedding light on the respective effects of DSeq-D and DSim-D. METHODS: Investigators systematically searched PubMed, EMBASE and Cochrane Central databases for randomized controlled trials (RCTs) and cohort studies from their inception until June 06, 2024. The rate of survival to hospital discharge was the primary outcome, while the incidence of return of spontaneous circulation (ROSC), termination of ventricular fibrillation (VF), survival to hospital admission and good neurologic outcome were secondary outcomes. Relative ratios (RR) and 95% confidence intervals (CIs) were calculated for each outcome. Heterogeneity was assessed using I square value. RESULTS: A total of 6 trials, comprising 1360 patients, were included. One was an RCT, and five were observational cohort studies. The RCT showed that, compared to standard defibrillation, DSeq-D was associated with higher incidences of survival to hospital discharge, termination of VF, ROSC and good neurologic outcome. However, the pooled results of cohort studies found no benefit of DD over standard defibrillation in survival to hospital discharge (RR, 0.91; 95% CI, 0.46-1.78), nor in secondary outcomes. Furthermore, subgroup analysis suggested DSim-D was linked with lower ROSC rate compared to standard defibrillation (RR, 0.65; 95% CI, 0.49-0.86), while there was no significance between DSeq-D and standard defibrillation (RR, 1.00; 95% CI, 0.70-1.42). CONCLUSIONS: The benefit of DSeq-D in survival to hospital discharge for RVF patients was found in the RCT, but not in cohort studies. Additionally, DSim-D should be applied with greater caution for RVF patients. Further validation is needed through larger-scale and higher-quality trials. TRIAL REGISTRY: INPLASY; Registration number: INPLASY202340015; URL: https://inplasy.com/.

Cost-effectiveness analysis of leadless cardiac resynchronization therapy.

BACKGROUND: The Wireless Stimulation Endocardially for CRT (WiSE-CRT) system is a novel technology used to treat patients with dyssynchronous heart failure (HF) by providing leadless cardiac resynchronization therapy (CRT). Observational studies have demonstrated its safety and efficacy profile, however, the treatment cost-effectiveness has not previously been examined. METHODS: A cost-effectiveness evaluation of the WiSE-CRT System was performed using a cohort-based economic model adopting a "proportion in state" structure. In addition to the primary analysis, scenario analyses and sensitivity analyses were performed to test for uncertainty in input parameters. Outcomes were quantified in terms of quality-adjusted life year (QALY) differences. RESULTS: The primary analysis demonstrated that treatment with the WiSE-CRT system is likely to be cost-effective over a lifetime horizon at a QALY reimbursement threshold of £20 000, with a net monetary benefit (NMB) of £3781 per QALY. Cost-effectiveness declines at time horizons shorter than 10 years. Sensitivity analyses demonstrated that average system battery life had the largest impact on potential cost-effectiveness. CONCLUSION: Within the model limitations, these findings support the use of WiSE-CRT in indicated patients from an economic standpoint. However, improving battery technology should be prioritized to maximize cost-effectiveness in times when health services are under significant financial pressures.

Rationale and design of the Lead Evaluation for Defibrillation and Reliability study: Safety and efficacy of a novel ICD lead design.

BACKGROUND: Implantable cardioverter defibrillators (ICD) are indicated for primary and secondary prevention of sudden cardiac arrest. Despite enhancements in design and technologies, the ICD lead is the most vulnerable component of the ICD system and failure of ICD leads remains a significant clinical problem. A novel, small-diameter, lumenless, catheter-delivered, defibrillator lead was developed with the aim to improve long-term reliability. METHODS AND RESULTS: The Lead Evaluation for Defibrillation and Reliability (LEADR) study is a multi-center, single-arm, Bayesian, adaptive design, pre-market interventional pivotal clinical study. Up to 60 study sites from around the world will participate in the study. Patients indicated for a de novo ICD will undergo defibrillation testing at implantation and clinical assessments at baseline, implant, pre-hospital discharge, 3 months, 6 months, and every 6 months thereafter until official study closure. Patients may be participating for a minimum of 18 months to approximately 3 years. Fracture-free survival will be evaluated using a Bayesian statistical method that incorporates both virtual patient data (combination of bench testing to failure with in-vivo use condition data) with clinical patients. The clinical subject sample size will be determined using decision rules for number of subject enrollments and follow-up time based upon the observed number of fractures at certain time points in the study. The adaptive study design will therefore result in a minimum of 500 and a maximum of 900 patients enrolled. CONCLUSION: The LEADR Clinical Study was designed to efficiently provide evidence for short- and long-term safety and efficacy of a novel lead design using Bayesian methods including a novel virtual patient approach.

Voltage gradients in transvenous and subcutaneous defibrillation and their risk of myocardial damage.

INTRODUCTION: Transvenous implantable cardioverter-defibrillator (ICD) shocks have been associated with cardiac biomarker elevations and are thought in some cases to contribute to adverse clinical outcomes and mortality, possibly from myocardium exposed to excessive shock voltage gradients. Currently, there are only limited data for comparison with subcutaneous ICDs. We sought to compare ventricular myocardium voltage gradients resulting from transvenous (TV) and subcutaneous defibrillator (S-ICD) shocks to assess their risk of myocardial damage. METHODS: A finite element model was derived from thoracic magnetic resonance imaging (MRI). Voltage gradients were modeled for an S-ICD with a left-sided parasternal coil and a left-sided TV-ICD with a mid-cavity, a septal right ventricle (RV) coil, or a dual coil lead (TV mid, TV septal, TV septal + superior vena cava [SVC]). High gradients were defined as > 100 V/cm. RESULTS: The volumes of ventricular myocardium with high gradients > 100 V/cm were 0.02, 2.4, 7.7, and 0 cc for TV mid, TV septal, TV septal + SVC, and S-ICD, respectively. CONCLUSION: Our models suggest that S-ICD shocks produce more uniform gradients in the myocardium, with less exposure to potentially damaging electrical fields, compared to TV-ICDs. Dual coil TV leads yield higher gradients, as does closer proximity of the shock coil to the myocardium.

Propofol dose and efficacy of defibrillation testing during implantation of subcutaneous implantable cardioverter-defibrillators: A retrospective, single center cohort study.

INTRODUCTION: Defibrillation testing (DFT) is recommended during subcutaneous implantable cardioverter-defibrillator (S-ICD) implantation. Previous studies analyzing the potential interference of propofol with defibrillation threshold are inconsistent. The purpose of this study was to analyze whether propofol affects DFT post S-ICD placement. METHODS: All patients with S-ICD implantation between 01/2017 and 11/2020 at the University Heart Center Freiburg were retrospectively analyzed. Two groups were generated depending on the success of the first shock during DFT. Implantation characteristics and dose of anesthetics were analyzed. RESULTS: In 12 of the included 80 (15%) patients, first shock during DFT failed. The absolute dose of propofol was significantly higher in patients with first shock failure (median 653 mg [IQR 503-855]) compared to patients with first shock termination (376 mg [200-600]; p = 0.027). Doses of opioids and midazolam as well as type of anesthesia did not differ between the groups. A multivariable binary logistic regression analysis confirmed an independent association of first shock termination and propofol dose (per 100 mg: OR 0.73 (95% CI: 0.56-0.95); p = 0.021). CONCLUSION: There is an independent association of propofol dose and first shock failure in routine S-ICD defibrillation testing.

The relationship between the incision line and position of the latissimus dorsi muscle for subcutaneous implantable cardioverter-defibrillator intermuscular implantations.

INTRODUCTION: Intermuscular implantations of subcutaneous implantable cardioverter-defibrillators (S-ICD) have been recommended, but the position of the anterior border of the latissimus dorsi muscle (LDM) has not previously been evaluated in establishing an incision line to facilitate the intermuscular approach. The objective of this study is to evalua the position and trend of the anterior border of the LDM in patients who are candidates for implantable cardioverter-defibrillators. METHODS: The distance from the back to the anterior border of the LDM (A) and the anterior-posterior width of the chest wall (B) were measured on computed tomography retrospectively, and the ratio (=A/B) was used as the position of the anterior border of the LDM. In addition, the variability and factors affecting the values were evaluated. RESULTS: An analysis was performed on 78 patients, and the position of the anterior border of the LDM (=A/B) exhibited a normal distribution, with a mean value of 0.53 ± 0.062 (0.41-0.69). The position of the anterior border of the LDM tended to be more anterior in younger, taller, male, primary prevention, nonheart failure, low brain natriuretic peptide level, and nondiabetic patients. CONCLUSION: The position of the anterior border of the LDM varied from case to case with variable results. Conventional incisions on the midaxillary line may be inappropriate for intermuscular implantations, and the position of the anterior border of the LDM should be evaluated in each individual case to establish the incision line.

Implantable defibrillator-detected heart failure status predicts ventricular tachyarrhythmias.

INTRODUCTION: The prediction of ventricular tachyarrhythmias among patients with implantable cardioverter defibrillators is difficult with available clinical tools. We sought to assess whether in patients with heart failure (HF) and reduced ejection fraction with defibrillators, physiological sensor-based HF status, as summarized by the HeartLogic index, could predict appropriate device therapies. METHODS: Five hundred and sixty-eight consecutive HF patients with defibrillators (n = 158, 28%) or cardiac resynchronization therapy-defibrillators (n = 410, 72%) were included in this prospective observational multicenter analysis. The association of both HeartLogic index and its physiological components with defibrillator shocks and overall appropriate therapies was assessed in regression and time-dependent Cox models. RESULTS: Over a follow-up of 25 (15-35) months, 122 (21%) patients received an appropriate device therapy (shock, n = 74, 13%), while the HeartLogic index crossed the threshold value (alert, HeartLogic ≥ 16) 1200 times (0.71 alerts/patient-year) in 370 (65%) subjects. The occurrence of ≥1 HeartLogic alert was significantly associated with both appropriate shocks (Hazard ratios [HR]: 2.44, 95% confidence interval [CI]: 1.49-3.97, p = .003), and any appropriate defibrillator therapies. In multivariable time-dependent Cox models, weekly IN-alert state was the strongest predictor of appropriate defibrillator shocks (HR: 2.94, 95% CI: 1.73-5.01, p < .001) and overall therapies. Compared with stable patients, patients with appropriate shocks had significantly higher values of HeartLogic index, third heart sound amplitude, and resting heart rate 30-60 days before device therapy. CONCLUSION: The HeartLogic index is an independent dynamic predictor of appropriate defibrillator therapies. The combined index and its individual physiological components change before the arrhythmic event occurs.

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.

Outcome and safety of intraoperative defibrillation testing during device replacement: the Simpler trial.

AIMS: Intraoperative defibrillation testing (DT) during implant or replacement of implantable cardioverter-defibrillators (ICDs) has been a matter of debate for many years. This debate was put to rest by the Simple and Nordic ICD trials, and the practice of testing during new implantations has essentially been almost abandoned. Old registries demonstrated an increased incidence of significant findings in DT during replacements. The aim of the present study was to evaluate frequency of significant findings and safety of DT in subjects undergoing device replacement. METHODS AND RESULTS: A prospective observational multi-centre study included consecutive patients undergoing ICD generator replacement. The primary outcome was a failure to terminate induced ventricular fibrillation (VF) with a single shock 10 J below the maximal capacity of the device. Secondary outcomes included complications of DT. Patients were followed-up at 1- and 6-months post-procedure. A total of 92 patients were eligible, and consented to the study, of which 84 underwent DT during battery replacement. The median age was 68 years and 79.8% were males. Induction of VF was successful in 84 patients as was a successful conversion on the first attempt in all. There were no procedure-related complications. During follow up one patient had two appropriate ICD shock events. In four patients, ICD programming was changed. None suffered inappropriate shock. There was no evidence of lead malfunction. Two deaths occurred, none of which was related to arrhythmia. CONCLUSION: The present study found DT was not associated with complications in patients undergoing ICD generator replacement but produced no clinically important information.

Sports-related sudden cardiac arrest in young adults.

AIMS: Data on sports-related sudden cardiac arrest (SrSCA) among young adults in the general population are scarce. We aimed to determine the overall SrSCA incidence, characteristics, and outcomes in young adults. METHODS AND RESULTS: Prospective cohort study of all cases of SrSCA between 2012 and 2019 in Germany and Paris area, France, involving subjects aged 18-35 years. Detection of SrSCA was achieved via multiple sources, including emergency medical services (EMS) reporting and web-based screening of media releases. Cases and aetiologies were centrally adjudicated. Overall, a total of 147 SrSCA (mean age 28.1 ± 4.8 years, 95.2% males) occurred, with an overall burden of 4.77 [95% confidence interval (CI) 2.85-6.68] cases per million-year, including 12 (8.2%) cases in young competitive athletes. While bystander cardiopulmonary resuscitation (CPR) was initiated in 114 (82.6%), automated external defibrillator (AED) use by bystanders occurred only in a minority (7.5%). Public AED use prior to EMS arrival (odds ratio 6.25, 95% CI 1.48-43.20, P = 0.02) was the strongest independent predictor of survival at hospital discharge (38.1%). Among cases that benefited from both immediate bystander CPR and AED use, survival rate was 90.9%. Coronary artery disease was the most frequent aetiology (25.8%), mainly through acute coronary syndrome (86.9%). CONCLUSION: Sports-related sudden cardiac arrest in the young occurs mainly in recreational male sports participants. Public AED use remains disappointingly low, although survival may reach 90% among those who benefit from both bystander CPR and early defibrillation. Coronary artery disease is the most prevalent cause of SrSCA in young adults.

Additional coils mitigate elevated defibrillation threshold in right-sided implantable cardioverter defibrillator generator placement: a simulation study.

AIMS: The standard implantable cardioverter defibrillator (ICD) generator (can) is placed in the left pectoral area; however, in certain circumstances, right-sided cans may be required which may increase defibrillation threshold (DFT) due to suboptimal shock vectors. We aim to quantitatively assess whether the potential increase in DFT of right-sided can configurations may be mitigated by alternate positioning of the right ventricular (RV) shocking coil or adding coils in the superior vena cava (SVC) and coronary sinus (CS). METHODS AND RESULTS: A cohort of CT-derived torso models was used to assess DFT of ICD configurations with right-sided cans and alternate positioning of RV shock coils. Efficacy changes with additional coils in the SVC and CS were evaluated. A right-sided can with an apical RV shock coil significantly increased DFT compared to a left-sided can [19.5 (16.4, 27.1) J vs. 13.3 (11.7, 19.9) J, P < 0.001]. Septal positioning of the RV coil led to a further DFT increase when using a right-sided can [26.7 (18.1, 36.1) J vs. 19.5 (16.4, 27.1) J, P < 0.001], but not a left-sided can [12.1 (8.1, 17.6) J vs. 13.3 (11.7, 19.9) J, P = 0.099). Defibrillation threshold of a right-sided can with apical or septal coil was reduced the most by adding both SVC and CS coils [19.5 (16.4, 27.1) J vs. 6.6 (3.9, 9.9) J, P < 0.001, and 26.7 (18.1, 36.1) J vs. 12.1 (5.7, 13.5) J, P < 0.001]. CONCLUSION: Right-sided, compared to left-sided, can positioning results in a 50% increase in DFT. For right-sided cans, apical shock coil positioning produces a lower DFT than septal positions. Elevated right-sided can DFTs may be mitigated by utilizing additional coils in SVC and CS.

Exploiting SMART pass filter deactivation detection to minimize inappropriate subcutaneous implantable cardioverter defibrillator therapies: a real-world single-centre experience and management guide.

AIMS: The SMART Pass™ (SP) algorithm is a high-pass filter that aims to reduce inappropriate therapy (IT) in subcutaneous internal cardiac defibrillator (S-ICD), but SP can deactivate due to low amplitude sensed R waves or asystole. The association between IT and SP deactivation and management strategies were evaluated, hypothesizing SP deactivation increases the risk of IT and device re-programming, or lead/generator re-positioning could reduce this risk. METHODS AND RESULTS: Retrospective single-centre audit of Emblem™ S-ICD devices implanted 2016 to 2020 utilizing health records and remote monitoring data. Cox regression models evaluated associations between SP deactivation and IT. A total of 348 patients (27 ± 16.6 months follow-up) were studied: 73% primary prevention. Thirty-eight patients (11.8%) received 83 shocks with 27 patients (7.8%) receiving a total of 44 IT. Causes of IT were oversensing (98%) and aberrantly conducted atrial fibrillation (2%). SP deactivation occurred in 32 of 348 patients (9%) and was significantly associated with increased risk of IT (hazard ratio 5.36, 95% CI 2.37-12.13). SP deactivation was due to low amplitude R waves (94%), associated with a higher defibrillation threshold at implant and presence of arrhythmogenic right ventricular cardiomyopathy. No further IT occurred 16 ± 15.5 months after corrective interventions, with changing the sensing vector being successful in 59% of cases. CONCLUSION: To reduce the risk of IT, the cause of the SP deactivation should be investigated, and appropriate reprogramming, device, or lead modifications made. Utilizing the alert for SP deactivation and electrograms could pro-actively prevent IT.