ICDs are implanted to treat sudden arrhythmic death by treating episodes of ventricular arrhythmia (VA). Despite this primary function, patients can still die with a functioning ICD due to untreated VA. The purpose of this review is to examine the causes and implications of ICD failures in detection and therapy delivery during VA and assess post-mortem interrogation practices and literature. The literature, adverse event reports, and the authors’ own internal data were reviewed to identify causes of ICD non-therapy. Signal-related, functional, algorithmic and myocardial undersensing were identified as contributors, along with episodes of failed defibrillation/cardioversion. Contemporary ICD programming prioritises specificity but may compromise sensitivity. Post-mortem interrogation is rare, under-utilised and has no standardisation, despite reports of ICD failure being the cause of death in up to 25% of cases. To conclude, failure to interrogate ICDs after death risks missing fatal undersensing. Systematic post-mortem analysis is proposed as the cardiac equivalent of aviation’s black box, which is critical for learning and sudden arrhythmic death prevention.

BACKGROUND:The subcutaneous implantable cardioverter defibrillators (S-ICD) in hypertrophic cardiomyopathy (HCM) remains controversial. HCM patients are often younger and exposed to longer-term risks: complications and inappropriate therapy (IT). The S-ICD avoids vascular risks associated with transvenous ICDs (TV-ICD), but the rate of IT remains a concern. We conducted a retrospective observational study in HCM patients who received ICDs: assessing outcomes and utilizing a multi-event statistical model, we provide a novel assessment of the cumulative complication risk. METHODS:A retrospective study of all HCM patients who received an ICD at a tertiary center from 2006 to 2022 was conducted, utilizing electronic pacing and health records. Cox-proportion hazard models were applied for comparative outcome analysis and a multi-event statistical model was used to assess the cumulative burden of complications. Propensity score matching was used to adjust for baseline differences. RESULTS:We analysed data from 611 patients, with 141 receiving S-ICDs (26.7%). S-ICD patients had significantly fewer complications over a maximal follow-up of 137 months (HR 0.309, 95% CI 0.103-0.923, p = 0.035). Multi-event analysis demonstrated a cumulative increase in complications over time for TV-ICD patients (HR 0.258, 95% CI 0.109-0.644, p = 0.004), conversely no S-ICD patients experienced multiple complications. There was no difference in therapy rates or mortality between matched groups. CONCLUSION:The S-ICD is associated with fewer complications than TV-ICD, this is amplified by multi-event analysis, but without differences in IT. This should be discussed with HCM patients, as the S-ICD could provide a better benefit/risk ratio.

More socioeconomically deprived patients have worse cardiovascular outcomes. However, relationships between socioeconomic status (SES) and implantable cardioverter defibrillator (ICD) therapy have not been studied. To determine whether patients with more deprived SES experience different rates of ICD therapy. Retrospective analysis of patients who received an ICD at a single tertiary cardiac centre from 2017 to 2020. SES was computed utilising the Indices of Multiple Deprivation (IMD) and patient’s postcode at date of implant. IMD is produced from the domains: income; employment; health deprivation and disability; education, skills training; crime; barriers to housing and services; living environment. Baseline variables included device type, implant indication, ICD programming, cardiovascular risk factors and medications. ICD therapies were classified as appropriate (AT) for ventricular tachycardia (VT) or ventricular fibrillation (VF), and inappropriate (IT) for all other therapies. Devices were programmed with ICD therapy zones enabled at 200 BPM or above. Univariate and multivariate Cox regressions were used to identify predictors, and Fine-Gray competing risk models to assess the thresholds of deprivation rank on therapy outcomes. The cohort included 844 patients with a follow-up duration of 625 ± 306 days. Lower SES (more deprived) patients showed a trend toward increased AT in the multivariate Cox model, with a hazard ratio (HR) of 1.000 (95% CI: 0.999–1.000, p = 0.023). The upper three SES quartiles showed a 48.4% reduction in the AT/annualised event rate compared to the lowest quartile (0.044 vs 0.085 events per patient-year). The Fine-Gray competing risks model confirmed these with a HR of 0.50 (95% CI: 0.32–0.77, p = 0.0017) for the lowest deprivation quartile (Figure 1). Interestingly, deprivation rank was not associated with IT in univariate or multivariate analyses. Our findings indicate that patients who reside in the lowest quartile of deprived areas are more likely to experience AT from their ICD, without any association with IT. This suggests that SES factors are related to the occurrence of VT or VF. These could be related to chronic stress levels and increased sympathetic drive triggering arrhythmias as well as factors influencing cardiovascular risk, medical compliance and healthcare support. These data highlight the importance of considering SES in management of ICD patients. Clinicians, service managers and policymakers should be aware of the SES disparities to provide equity in ICD outcomes. Further research is needed to assess the specific factors and mechanisms causing this trend to create a more personalised care package for ICD patients to improve outcomes.Figure 1

Longer rhythm monitoring in ischaemic stroke patients increases rate of Atrial Fibrillation (AF) detection (1,2). However, prolonged rhythm monitoring is expensive and inappropriate for patients that are already diagnosed with AF. Conversely, pathways reliant on human factors can delay or miss indicated investigations. The extent of inappropriate and missed investigations is unknown as is whether pathways for AF detection can reduce inappropriate requests and improve rate of AF diagnosis. To evaluate the impact of a dynamic sequential AF detection pathway on outcomes and workload in a large specialist stroke service. Investigations and outcomes were reviewed in patients with ischemic stroke/TIA admitted to a large tertiary stroke service between January-March 2023. AF prevalence and detection on admission ECG and Holter/Zio monitoring were recorded as outcomes to determine appropriateness of onward investigation. Figure 1 outlines the interval pathway introduced to the service on 5th September 2023 based on National Guidance (3,4). Practice was re-evaluated in April-May 2024. The study was prospectively registered and endorsed by the Local Clinical Effectiveness Unit (study number 12024). Between January-March 2023, 109 people were admitted with an ischaemic stroke (n=98) or TIA (n=11). 13 patients had new AF detected on admission 12-lead ECG and 14 patients had known AF. 6/27 (22%) with known or newly diagnosed AF on admission ECG were inappropriately referred for further Holter/Zio monitoring for AF detection. 64/82 (78%) patients without an AF diagnosis had Holter/Zio monitoring requested. Of the 35 completed requests, 33 (94%) showed no AF. 0/33 (0%) had documented consideration or referral for implantable continuous monitoring (ICM). Between April-May 2024, after implementation of the AF detection pathway, 85 patients were admitted with an ischaemic stroke (n=81) or TIA (n=4). 2/27 (7%) patients with new or known AF were referred for Holter monitoring (X2 (1, N=130)=1.53, p=0.22). 58/58 (100%) patients without an AF diagnosis underwent Holter/Zio monitoring (X2 (1, N=140)=12.08, p<0.05) but no patients were considered for ICM. AF was detected in 2/35 (6%) patients with Holter/Zio monitoring between January-March 2023 compared to 1/21 (5%) patients in April-May 2024 (X2 (1, N=56)=0.02, p=0.88). 66/122 (54%) Holter/Zio requests from January-March 2023 (n=29) and April-May 2024 (n=37) are still being processed. Inappropriate AF investigations are frequent, while indicated prolonged monitoring may be delayed or missed. A dynamic, sequential pathway can reduce unnecessary tests and ensure access to appropriate monitoring. Longer-term follow-up of clinical outcomes and AF detection is warranted.

An implantable loop recorder is a device that can be surgically inserted into a patient to continuously monitor cardiac activity over a longer period of time. Data from these devices can be sent directly to a smartphone app and shared with the clinical team, allowing the patient to be monitored in the community. Implantable loop recorders are used to diagnose the causes of conditions such as syncope and detect atrial fibrillation in high-risk individuals. This article discusses the LINQ II device (Medtronic), an implantable loop recorder that has been developed to detect heart rhythms more effectively, handle larger quantities of data, improve the patient experience and streamline clinical workflows. The authors discuss the features and uses of this device, including an example of its implementation in a major NHS hospital in London.

Temporary epicardial pacing is a cornerstone of postoperative cardiac care, but improper management, particularly of atrial pacing, may contribute to the onset of postoperative atrial fibrillation (POAF). In this article we review the challenges involved in identifying atrial lead malfunction and the associated arrhythmogenic risk. As well as implementing strategies to reduce risk, the development of advanced technology capable of detecting and correcting atrial pacing dysfunction in real time should be a priority.

Current guidelines recommend to perform a defibrillation test (DFT) when a subcutaneous implantable cardioverter defibrillator replacement is performed. For transvenous ICD systems there is evidence that this can be safely omitted but evidence is lacking for patients that have a subcutaneous implantable cardioverter defibrillator implanted. To evaluate pre-procedural parameters that can predict the outcome of the DFT so this may safely be avoided. A retrospective multicenter analysis of subcutaneous implantable cardioverter defibrillator patients undergoing a device replacement with or without DFT was performed. The cohort included 151 patients: 121 male, age 60.9±16.4 year, LVEF 40.5±7.1, primary prevention 65%. In total 176 device replacements where included. At first implant 136 patients ( 92.5%) had a DFT with a single 65J shock success rate of 93.4%. At first implant the average shock impedance was 77(±21). A Praetorian scores of 30-90 was achieved in 71 (60.2%) of the patients. Only 7 (5,9%) had a score ≥ 150 but still successful DFT. During first replacement 55% of the patients (83) underwent DFT testing with a 90,4% single shock success rate. Only 8 patients needed a second DFT. At the second replacement 9 Patients (36%) were tested with a single shock success rate of 100%. X rays were made in 55 (36,4%) and 5 (20,8%) before first or second replacement. X rays showed that 45 patients (84,9%) had a stabile lead position at first replacement and 3 patients (60%) at second replacement. A unstable position might influence the impedance or the Praetorian score in a negative way on shock conversion capability. Average shock impedance was 90 Ohm(± 25) at first replacement and 72 (±22) at second replacement. A high impedance lowers the power of the delivered shock and influence the efficacy of the DFT. More than 60% of the patients had a Praetorian scores of 30-90. Only 3 patients ( 5.9%) at first replacement had a score of ≥ 150. The praetorian score estimates the risk of conversion failure. A praetorian score of ≥ 90 has a positive predictive value of 25% for failed DFT. It is feasible to safely avoid the DFT test if certain precautionary measures are performed before the device replacement. Comparing X-ray, Praetorian score and impedance measurements with the values of first implant can assist in making the decision of avoiding the DFT testing.

The use of Subcutaneous Implantable Cardioverter Defibrillator (S-ICD) in Hypertrophic cardiomyopathy (HCM) remains controversial. HCM patients are commonly younger, exposing them to longer-term risks, such as complications and inappropriate therapy (IT). The S-ICD avoids vascular risks associated with transvenous ICDs (TV-ICD), but the rate of IT and lack of antitachycardia pacing (ATP) remain a concern. We investigated outcomes of HCM patients who received S-ICD and TV-ICD, assessing ICD therapy outcomes, and, utilising a multi-event statistical model to provide a novel, complete assessment of cumulative complication risk. A retrospective audit of all HCM patients who received an ICD at a large tertiary centre from 2006 to 2022 was conducted, using electronic pacing and health records. A multi event statistical model (Lin Wei Yang Yin) was used to assess the cumulative burden of complications. Propensity score matching was used to adjust for baseline differences and Cox-proportion hazard models were applied for comparative outcome analysis that were conducted independently (e.g. first IT for IT analysis and first complication for complication analysis). We reviewed 611 patients, (mean age of 48.7 ± 14.5 years) with 470 receiving TV-ICDs (73.3%) and 141 S-ICD patients. TV-ICD patients had a significantly longer follow up than S-ICD patients; 83.46 ± 68.43 months vs 41.80 ± 30.40 months (p<0.001). TV-ICD patients had significantly more complications than S-ICD patients (21.7% vs 2.8%, p<0.001), mostly due to lead-related complications, that were more common in the TV-ICD group (Table 1). Multi-event analysis demonstrated a cumulative increase in complications over time for TV-ICD patients. No S-ICD patients experienced multiple complications through follow up, although some had advisory shorter than expected battery life. This was primarily due to lead-related issues and device infections. Interestingly many of the multiple complications occured after 150 months time period. There was no difference in inappropriate and appropriate therapy rates between both groups. The S-ICD is associated with less complications over 120-month follow-up compared to TV-ICD in HCM patients, without significant difference in IT. The multi-event statistical methods highlight the importance of cumulative risk over time, with the compound risk of complication increasing as leads begin to fail after 150 months. Longer-term follow-up is required for SICD comparisons; however, our data suggests the SICD to be a potentially safer device in the long term for HCM patients. This should be discussed with HCM patients at consultation for ICD therapy, as the S-ICD provided a better benefit / risk ratio over 10 years follow up.Figure 1

Implantable Cardioverter Defibrillators (ICDs) have undergone substantial evolution since the 1980s, with the aim of decreasing sudden cardiac death, whilst minimising device related complications. Traditional transvenous ICDs (TV-ICDs), though comprehensive and effective, are associated with risks with having leads inside the veins and heart. The emergence of the subcutaneous ICD (S-ICD) offered a solution for patients without a pacing indication, significantly reducing the risks of complications acutely and long term. The absence of pacing and need for specific ECG requirements limit its usability for all ICD patients. The extravascular ICD (EV-ICD) has attempted to provide a solution using a substernal lead position and warrants further investigation into its usability. Recent innovations of modular ICD therapy, combining the S-ICD with a leadless pacemaker, that communicate to deliver painless anti-tachycardia pacing and single chamber pacing could be the comprehensive solution.This review examines the strengths and limitations of these ICD technologies, drawing on current available data in 2025. We critically appraise the literature and discuss perspectives on recent evidence in ICD studies.As technology advances, the selection of the type of ICD should be guided by the risk and benefit, particularly with the perceived lower benefit from more modern medical management and programming. Patients should be fully informed of the risks and benefits of devices that they are being offered, guided by evidence. With the expanding capabilities of modern ICDs and remote monitoring, the future of ICD therapy maybe increasingly customisable and tailored for the individual.

Background Subcutaneous implantable cardiac defibrillator (SICD) efficacy can be affected by increased body habitus due to R wave undersensing and unsuccessful defibrillation from ineffectual current delivery.Case summary Our patient underwent SICD implantation for idiopathic VF. Appropriate shocks were delivered over the next 4 years for episodes of VF storm. However, following this his weight increased from 102 to 167 kg. With this his R wave values in all vectors fell, and device impedance rose to 210 ohm. This value was outside manufacturer recommendations and where its efficacy in treating ventricular arrhythmia is unknown. Due to this concern, a full system revision procedure occurred, following which his impedance fell to 80 ohm, and he successfully underwent defibrillation testing. At follow up he had remained arrhythmia free with normal device parameters and had commenced a weight loss programme.Discussion Increased body habitus can have profound effects of SICD parameters due to the high resistance of adipose tissue. Parameters and device efficacy can be optimized with device and lead placement adjacent to the chest wall and sternum respectively.

BACKGROUND There is a paucity of data comparing vitamin K antagonists (VKAs) to direct oral anticoagulants (DOACs) at the time of cardiac implantable electronic device (CIED) surgery. Furthermore, the best management of DOACs (interruption vs continuation) is yet to be determined. OBJECTIVES This study aimed to compare the incidence of device -related bleeds and thrombotic events based on anticoagulant type (DOAC vs VKA) and regimen (interrupted vs uninterrupted). METHODS This was an observational multicenter study. We included patients on chronic oral anticoagulation undergoing CIED surgery. Patients were matched using propensity scoring. RESULTS We included 1,975 patients (age 73.8 +/- 12.4 years). Among 1,326 patients on DOAC, this was interrupted presurgery in 78.2% (n =1,039) and continued in 21.8% (n = 287). There were 649 patients on continued VKA. The matched population included 861 patients. The rate of any major bleeding was higher with continued DOAC (5.2%) compared to interrupted DOAC (1.7%) and continued VKA (2.1%) (P = 0.03). The rate of perioperative thromboembolism was 1.4% with interrupted DOAC, whereas no thromboembolic events occurred with DOAC or VKA continuation (P = 0.04). The use of dual antiplatelet therapy, DOAC continuation, and male sex were independent predictors of major bleeding on a multivariable analysis. CONCLUSIONS In this large real -world cohort, a continued DOAC strategy was associated with a higher bleeding risk compared to DOAC interruption or VKA continuation in patients undergoing CIED surgery. However, DOAC interruption was associated with increased thromboembolic risk. Concomitant dual antiplatelet therapy should be avoided whenever clinically possible. A bespoke approach is necessary, with a strategy of minimal DOAC interruption likely to represent the best compromise. (J Am Coll Cardiol EP 2024;10:121-132) (c) 2024 by the American College of Cardiology Foundation.

We describe two cases of secondary prevention subcutaneous implantable cardioverter defibrillator (S-ICD) implantation and subsequent S-ICD electrode displacement which initially went undetected. One presentation was a result of a coincidental chest x-ray for respiratory exacerbation and another with an untreated episode highlighted via remote monitoring, both patients were booked to clinic for further investigation. Our findings highlighted had there been a comparison of the existing subcutaneous electrogram (S-ECG) to captured S-ECGs at time of implant the electrode displacement would have been detected beforehand. This underpins the importance of introducing the simple management strategy into routine follow-up.

The transition of implantable loop recorder (ILR) explant procedures from physician to non-physician (NP) and from catheter labs (CL) to outpatient (OP) settings has not been as thoroughly investigated. We implemented a NP, OP ILR explant service in 2021, and hypothesized that it would have comparable safety outcomes, save time, and reduce costs.

In ambulatory patients with complete heart block (CHB), dual-chamber (DDD) pacing confers physiological benefits versus single-chamber (VVI) pacing, however, the impact on mortality is disputed. Nonagenarians constitute an expanding proportion of pacemaker recipients, yet data on device selection and outcomes are limited, especially in emergency situations. In nonagenarians with emergent CHB, we compared the clinical characteristics and outcomes of patients receiving VVI versus DDD pacemakers. Cox proportional-hazards analysis examined all-cause mortality and death from congestive cardiac failure (CCF). There were 168 consecutive patients followed-up for 30.6 ± 15.5 months. Of these, 22 patients (13.1%) received VVI pacemakers; when compared with DDD recipients, these patients had similar median age (93 vs. 91 years, p=0.15) and left ventricular (LV) systolic function (LV ejection fraction [EF] 49.2% ± 9.7 vs. 50.7% ± 10.1, p=0.71), but were more frail (Rockwood scale 5.2 ± 1.8 vs. 4.3 ± 1.1, p=0.004) and more likely to have dementia (27.3% vs. 8.9%, p=0.011). Post-implant, device interrogation demonstrated that VVI recipients had higher respiratory rates (21.3 ± 2.4 vs. 17.5 ± 2.6 breaths per minute, p=0.002), lower mean heart rates (65.5 ± 10.1 vs. 71.9 ± 8.6 bpm, p=0.002), and lower daily activity levels (0.57 ± 0.3 vs. 1.5 ± 1.1 hours of activity, p=0.016) than DDD recipients. Adjusting for age, frailty and dementia, VVI pacing was associated with an increased risk of all-cause mortality (adjusted hazard ratio [HR] 2.1, 95% confidence interval [CI] 1.08 to 4.1, p=0.03) and death from CCF (adjusted HR 7.1, 95%CI 2.5 to 20.6, p<0.001). In conclusion, in nonagenarians with emergent CHB, dual-chamber pacing was associated with improved symptomatic and prognostic outcomes versus singlechamber pacing.