Modern Implantable Cardioverter-defibrillator Research Articles

Assessment of Antitachycardia Pacing in Primary Prevention Patients

The emergence of novel programming guidelines that reduce premature and inappropriate therapies along with the availability of new implantable cardioverter-defibrillator (ICD) technologies lacking traditional endocardial antitachycardia pacing (ATP) capabilities requires the reevaluation of ATP as a first strategy in terminating fast ventricular tachycardias (VTs) in primary prevention ICD recipients. To assess the role of ATP in terminating fast VTs in primary prevention ICD recipients with contemporary programming. This global, prospective, double-blind, randomized clinical trial had an equivalence design with a relative margin of 35%. Superiority tests were performed at interim analyses and the final analysis if equivalence was not proven. Patients were enrolled between September 2016 and April 2021 at 134 sites in 8 countries, with the last date of follow-up on July 6, 2023. Patients were required to have an indication for a primary prevention ICD, including left ventricular ejection fraction less than or equal to 35%. Patients were randomized in a 1:1 ratio to receive ATP plus shock vs shock only. The primary end point was time to first all-cause shock. Secondary end points included time to first appropriate shock, time to first inappropriate shock, all-cause mortality, and the composite of time to first all-cause shock plus all-cause mortality. A total of 2595 patients were randomized (mean age, 63.9 years; 22.4% were females). At a mean follow-up of 38 months, first all-cause shock occurred in 129 participants in the ATP plus shock group and 178 participants in the shock only group. The hazard ratio (HR) for the primary end point was 0.72 (95.9% CI, 0.57-0.92), with P = .005 for superiority of the ATP plus shock group over the shock only group. During follow-up in an intention-to-treat analysis, the total shock burden per 100 patient-years was not statistically different, at 12.3 and 14.9, respectively (P = .70). The use of a single burst of ATP prior to shock in primary prevention ICD recipients with modern ICD detection programming prolonged the time to first all-cause ICD shock. ClinicalTrials.gov Identifier: NCT02923726.

Heart failure management guided by remote multiparameter monitoring: A meta-analysis

BackgroundSeveral implant-based remote monitoring strategies are currently tested to optimize heart failure (HF) management by anticipating clinical decompensation and preventing hospitalization. Among these solutions, the modern implantable cardioverter-defibrillator and cardiac resynchronization therapy devices have been equipped with sensors allowing continuous monitoring of multiple preclinical markers of worsening HF, including factors of autonomic adaptation, patient activity, and intrathoracic impedance. ObjectivesWe aimed to assess whether implant-based multiparameter remote monitoring strategy for guided HF management improves clinical outcomes when compared to standard clinical care. MethodsA systematic literature research for randomized controlled trials (RCTs) comparing multiparameter-guided HF management versus standard of care was performed on PubMed, Embase, and CENTRAL databases. Incidence rate ratios (IRRs) and associated 95% confidence intervals (CIs) were calculated using the Poisson regression model with random study effects. The primary outcome was a composite of all-cause death and HF hospitalization events, whereas secondary endpoints included the individual components of the primary outcome. ResultsOur meta-analysis included 6 RCTs, amounting to a total of 4869 patients with an average follow-up time of 18 months. Compared with standard clinical management, the multiparameter-guided strategy reduced the risk of the primary composite outcome (IRR 0.83, 95%CI 0.71–0.99), driven by statistically significant effect on both HF hospitalization events (IRR 0.75, 95%CI 0.61–0.93) and all-cause death (IRR 0.80, 95%CI 0.66–0.96). ConclusionImplant-based multiparameter remote monitoring strategy for guided HF management is associated with significant benefit on clinical outcomes compared to standard clinical care, providing a benefit on both hospitalization events and all-cause death.

Risk of occurrence of electromagnetic interference from the application of transcutaneous electrical nerve stimulation on the sensing function of implantable defibrillators.

Transcutaneous electrical nerve stimulation (TENS) is an established method for pain relief. But electrical TENS currents are also a source of electromagnetic interference (EMI). Thus, TENS is considered to be contraindicated in implantable cardioverter-defibrillator (ICD) patients. However, data might be outdated due to considerable advances in ICD and cardiac resynchronization therapy (CRT) filtering and noise protection algorithm technologies. The aim of this pilot safety study was to re-evaluate the safety of TENS in patients with modern ICDs. One hundred and seven patients equipped with 55 different models of ICD/CRT with defibrillators from 4 manufacturers underwent a standardized test protocol including TENS at the cervical spine and the thorax, at 2 stimulation modes-high-frequency TENS (80 Hz) and burst-mode TENS (2 Hz). Potential interference monitoring included continuous documentation of ECG Lead II, intracardiac electrograms and the marker channel. Electromagnetic interference was detected in 17 of 107 patients (15.9%). Most frequent were: interpretations as a premature ventricular beats (VS/S) in 15 patients (14%), noise reversion in 5 (4.6%) which resulted in temporary asynchronous pacing in 3 (2.8%), interpretation as ventricular tachycardia/ventricular fibrillation in 2 (1.9%), and premature atrial beat in 2 (1.9%) patients. Electromagnetic interference occurrence was influenced by position (chest, P < 0.01), higher current intensity (P < 0.01), and manufacturer (P = 0.012). Overall, only intermittent and minor EMI were detected. Prior to the use of TENS in patients with ICDs, they should undergo testing under the supervision of a cardiac device specialist.

Long-term outcomes among a cohort of 4296 implantable cardioverter-defibrillator patients: insights from the UMBRELLA study

Abstract Background Large observational real-world studies describing modern implantable cardioverter-defibrillator (ICD) populations with long-term follow-up are lacking. Purpose To assess the incidence of arrhythmias in a cohort of contemporary patients undergoing ICD implant from 2005 and 2017 and to analyze the arrhythmic risk and mortality according to their clinical profiles. Methods UMBRELLA (NTC01561144) is a prospective, multicentre, nationwide study of ICD patients followed by remote monitoring. All device information was automatically stored through the remote monitoring system and a blinded review of all the stored arrhythmic episodes was performed. The study outcomes were first appropriate ICD therapy and all-cause death. Results The study population consisted of 4296 patients (61.9±12.9 years, ischaemic cardiomyopathy (ICM): n=2150, dilated cardiomyopathy (DCM): n=1166, valvular heart disease (VHD): n=119, hypertrophic cardiomyopathy (HCM): n=294, arrhythmogenic right ventricular cardiomyopathy (ARVC): n=71, Brugada syndrome (BS): n=143, long QT syndrome (LQTS): n=43, and adult congenital heart disease (ACHD): n=60)). Primary prevention (PP) was the main indication (n=2758). During a mean follow-up of 46.6±27.3 months, 16,067 episodes of sustained ventricular arrhythmia (SVA) occurred in 1344 patients. Appropriate ICD therapy was delivered to 85.7% (n=13,767) episodes of SVA in 1173 patients (27.3% of population). A higher risk of first appropriate ICD therapy was observed in VHD (HR: 1.94, 95% CI: 1.43–2.62), ARVC (HR: 1.84, 95% CI: 1.28–2.66), ICM (HR: 1.51, 95% CI: 1.29–1.78), and DCM (HR: 1.28, 95% CI: 1.07–1.53) whereas patients with HCM (HR: 0.72, 95% CI: 0.54–0.96) and BS (HR: 0.25, 95% CI: 0.14–0.45) were at significantly lower risk (Figure 1A). In multivariate analysis (Table 1), age, gender, atrial fibrillation (AF), secondary prevention, LVEF ≤35%, and QRS width emerged as clinical predictors of appropriate ICD therapy, whereas CRT-D correlated with lower risk. An independently higher risk was found in DCM, VHD, and ARVC, and a lower risk in BS patients. At follow-up, 590 deaths (13.4% of population) were reported. Patients with ICM (HR 3.90, 95% CI: 2.58–5.90), DCM (HR 3.33, CI 95%: 2.18–5.10), and VHD (HR 3.97, CI 95%: 2.25–6.99) had worse prognoses and it was significantly better in BS patients (HR 0.11, 95% CI: 0.01–0.67, p=0.017) (Figure 1B). In multivariate analysis, age, gender, AF, renal failure, diabetes and reduced LVEF, emerged as independent predictors of all-cause death (Table 1). Conclusions Irrespective of the aetiology, contemporary ICD patients with an arrhythmic substrate derived from left ventricular systolic dysfunction had a similar risk of ICD life-saving interventions and death. Funding Acknowledgement Type of funding sources: None. Table 1Figure 1

Electrical Storm in Patients with Inappropriate Implantable Cardioverter-Defibrillator Therapy: Current Trends in Clinical Practice between Guidelines and Technology Progress

The term “Electrical Storm” (ES) indicates cardiac electrical instability manifested by several episodes of ventricular tachyarrhythmias within a short time. In the contemporary implantable cardioverter-defibrillator (ICD) era, ES is defined as recurrent (three or more separate episodes) of ICD discharges over 24 hours. Some ESs are due to inappropriate repetitive shock and are potentially lethal for the patient. The most common causes of inappropriate ICD shock include supraventricular tachycardia with high ventricular response and oversening of peaked T waves or R wave, myopotentials or electrical noise. Appropriate diagnosis and treatment are critical in the Emergency Department. To approach these patients systematically, it is important to understand, that there are four causes of shock. Modern ICD incorporate sophisticated tachycardia detection algorithms within their programming designed to minimize devices’ detection mistakes and ICD-related information can also be checked using remote home monitoring systems. However, these opportunities are often not utilized to their full benefit. Thus, careful attention should be paid to the programming of the device. Fine tuning of the detection and differentiation algorithms is critical, and best done by a practitioner who understands the subtle differences among the different manufacturers. The racommendations for those problems should be revised.

Shoulder Function After Cardioverter-Defibrillator Implantation: 5-Year Follow-up

Implantable cardioverter-defibrillator (ICD) represents the main tool for prevention of sudden cardiac death. Different kinds of postimplant complications have been described; however, little is known about shoulder functional impairment and its impact on quality of life. Patients with standard indications for elective prepectoral subcutaneous ICD insertion were enrolled during a 1-year period. The impact of ICD implantation on shoulder motility, pain, general disability, and quality of life was evaluated prospectively at baseline, and after 2 weeks, 3 months, 1 year, and 5 years using the Constant score, the Numeric Pain Rating Scale, the Disabilities of the Arm, Shoulder, and Hand scale, and the Short Form-36 Health Survey questionnaire. A total of 50 patients underwent insertion of single, dual chamber, or biventricular ICDs. Two weeks after implantation, functional impairment and mild pain were observed in ipsilateral shoulder movements, with a reduction in the Short Form-36 Health Survey score. Shoulder functional impairment improved at the third-month evaluations, with almost normalization at 1-year and 5-year assessments, as well as pain and quality of life. Prepectoral subcutaneous ICD implantation may be associated with ipsilateral shoulder functional impairment that regresses partially after 3 months and completely at 1-year and 5-year assessments. The less invasive implantation technique and the relatively small size of modern ICDs, independently from types and volumes, may be relevant to the degree of postimplantation shoulder functional impairment and recovery time. Shoulder function should be assessed at routine checks, especially soon after ICD implantation because of potential functional impairment and subsequent impact on quality of life.

Knowledge of Implantable Cardioverter Defibrillator Purpose and Function Among Nurses in the United States.

Nurses play a crucial role in patient education and adaptation to having an implantable cardioverter defibrillator (ICD). The aim of this study was to assess cardiology nurses' knowledge and confidence in providing education and support to ICD recipients. A cross-sectional descriptive survey was used to assess nurses' knowledge and experience caring for ICD recipients in 2 academic medical centers in the Pacific Northwest, using an instrument developed in 2004 in the United Kingdom. Nurses (N = 74) worked on cardiology units or clinics, primarily held a baccalaureate degree or higher (85%), and had 16 years or more of nursing experience and 6 to 10 years of cardiology experience. The overall average knowledge score was 77%, with knowledge about modern ICD technology averaging 55%. Nurses' confidence, using 10-point scale, in preparing patients to receive an ICD implant was 6.32 ± 2.56, for preparing patients for discharge was 6.14 ± 2.43, and for providing education about ICD shocks was 6.63 ± 2.50. Nurses were most knowledgeable about factors that affect patient retention of knowledge and ICD-related environmental hazards. Nurses lacked knowledge about the basic ICD components, purpose of cardiac resynchronization, and dual-chamber ICDs. Factors associated with higher knowledge scores included past experience caring for a patient with an ICD and working in an electrophysiology outpatient clinic. The ICD knowledge of US nurses in 2015 was similar to that reported in the United Kingdom in 2004, with limited knowledge about the complexities of modern ICD devices. Such deficits in knowledge may affect the quality of education provided to ICD recipients in preparing them to live safely with an ICD.

Non-invasive programmed stimulation to identify high-risk patients with implanted cardioverter defibrillator (the NIPS-ICD study): study protocol for a randomized controlled trial.

BackgroundThe use of an implantable cardioverter defibrillator (ICD) is a widely used and effective therapy, which reduces the risk of cardiac death in many cardiac diseases, both implanted for secondary and primary prevention. However, recurrent arrhythmias and ICD discharges have adverse prognostic significance. Additional parameters that would identify patients who are at increased risk of arrhythmias and appropriate ICD interventions would be of clinical value. Modern ICDs are relatively complex devices with a number of functions, including the possibility to perform noninvasive programmed stimulation (NIPS) with an implanted electrode located in the right ventricle.Methods/DesignThe aim of the study is to evaluate the usefulness of NIPS in determining the likelihood of life-threatening arrhythmic events in patients with ICD. The study will include 150 consecutive patients with an ICD implanted both for primary and secondary prevention, regardless of etiology, who are followed in the outpatient clinic of our center and do not meet the exclusion criteria. A 12-step St. George’s Hospital NIPS protocol using ICD will be performed. The endpoint is to induce sustained ventricular arrhythmia (VT lasting more than 30 seconds or hemodynamically unstable VT/VF) or the end of the protocol. In case of serious and/or hemodynamically unstable heart rhythm disorders resistant to treatment with a low-energy antiarrhythmic pacing (ATP), the patient receives a short-term intravenous general anesthesia, and internal or external defibrillation is performed. Outpatient follow-up will be conducted during the pre-scheduled ICD control visits. An analysis of records of a registered memory device will be collected, a patient will be interviewed, and physical examination will be carried out. The follow-ups will be held every 3 months for 1 year. The primary endpoint of the follow-up will be appropriate intervention of ICD or sudden cardiac (arrhythmic) death; the secondary, appropriate ICD intervention, or death from cardiovascular causes; and the tertiary, appropriate ICD intervention, death or hospitalization for cardiovascular causes.DiscussionIt is expected that appropriate ICD interventions during follow-up will occur more often in patients who had sustained ventricular arrhythmias induced during NIPS.Clinical trials registryClinicalTrials.gov, NCT02373306, date of registration: 26 February 2015.

Single-coil and dual-coil defibrillator leads and association with clinical outcomes in a complete Danish nationwide ICD cohort

The best choice of defibrillator lead in patients with routine implantable cardioverter-defibrillator (ICD) is not settled. Traditionally, most physicians prefer dual-coil leads but the use of single-coil leads is increasing. The purpose of this study was to compare clinical outcomes in patients with single- and dual-coil leads. All 4769 Danish patients 18 years or older with first-time ICD implants from 2007 to 2011 were included from the Danish Pacemaker and ICD Register. Defibrillator leads were 38.9% single-coil leads and 61.1% dual-coil leads. The primary end point was all-cause mortality. Secondary end points were lowest successful energy at implant defibrillation testing, first shock failure in spontaneous arrhythmias, structural lead failure, and lead extraction outcomes. Single-coil leads were associated with lower all-cause mortality with an adjusted hazard ratio of 0.85 (95% confidence interval 0.73-0.99; P = .04). This finding was robust in a supplementary propensity score-matched analysis. However, dual-coil leads were used in patients with slightly higher preimplant morbidity, making residual confounding by indication the most likely explanation for the observed association between lead type and mortality. The lowest successful defibrillation energy was higher using single-coil leads (23.2 ± 4.3 J vs 22.1 ± 3.9 J; P < .001). No significant differences were observed for other secondary end points showing high shock efficacies and low rates of lead failures and extraction complications. Shock efficacy is high for modern ICD systems. The choice between single-coil and dual-coil defibrillator leads is unlikely to have a clinically significant impact on patient outcomes in routine ICD implants.

Programming Implantable Cardioverter-Defibrillator Therapy Zones to High Ranges to Prevent Delivery of Inappropriate Device Therapies in Patients With Primary Prevention: Results from the RISSY-ICD (Reduction of Inappropriate ShockS bY InCreaseD zones) trial

Inappropriate shock is a frequently seen clinical problem despite advanced technologies used in modern implantable cardioverter-defibrillator (ICD) devices. Our aim was to investigate whether simply raising the ICD detection zones can decrease inappropriate therapies while still providing appropriate therapy. We randomized 223 patients with primary prevention to either the conventional programming group with 3 zones as VT1 (167 to 182 beats/min) with discriminators, VT2 (182 to 200 beats/min) with discriminators, and ventricular fibrillation (>200 beats/min) (n=100) or the high-zone programming group with 3 zones as VT1 (171 to 200 beats/min) with discriminators, VT2 (200 to 230 beats/min) with discriminators, and ventricular fibrillation (>230 beats/min; n=101). Twenty-two patients were lost to follow-up. The primary objectives were the first episode of appropriate and inappropriate therapies. The secondary objectives were all-cause mortality and hospitalization for heart failure. During 12-month follow-up, the first episode of appropriate therapy was higher (22% vs 10%, hazard ratio [HR] 2.18, 95% confidence interval [CI], 1.09 to 4.36, p=0.028) and the first episode of inappropriate therapy was lower (5% vs 28%, HR 0.18 [95% CI 0.07 to 0.44], p<0.001) in the high-zone group compared with the conventional group. Although all-cause mortality did not differ (2% for the high-zone group vs 3% for the conventional group, HR 0.65 [95% CI 0.11 to 3.99], p>0.05), hospitalization for heart failure was significantly higher in the conventional group (13% vs 4%, HR 0.28 [95% CI 0.09 to 0.88], p=0.021). In conclusion, in a real-world population, high-zone settings of the single-, dual-, and triple-chamber ICDs were associated with reduction in inappropriate therapy while still providing appropriate therapy.

Is Defibrillation Testing Necessary for Implantable Transvenous Defibrillators?

Because the implantable cardioverter defibrillator (ICD) was introduced into clinical practice, insertion of these devices has typically involved defibrillation testing (DT). However, DT has never been shown to independently improve patient outcomes. The rationale for DT has always been that the induction of ventricular fibrillation (VF) immediately after ICD insertion allows the implanting team to verify that the ICD can appropriately sense VF and deliver a high-energy shock that can effectively terminate this arrhythmia.1 The first ICD systems were complex, using epicardial patches and monophasic shock waveforms, thus accurate sensing and termination of VF were frequently in question. However, the ICD evolved over time, with the introduction of transvenous systems, biphasic waveforms, and active cans, which made failure to sense and treat VF much less common.2,3 Modern ICDs are also capable of delivering energies >40 J, thus many have started to question the rationale for DT in the modern era.4–7 Response by Russo et al on p 351 During the past 10 years, there has been a dramatic shift in practice, such that DT is performed in <50% of ICD implants in some jurisdictions. This change was not driven by the results of randomized trials, but by changing opinions of clinicians,4 based on the following insights from observational studies: (1) intraoperative DT is usually successful and clinicians do not always act on unfavorable results; (2) intraoperative DT is an unproven surrogate for clinical shock efficacy; (3) the likelihood of a failed appropriate clinical shock is low and does not appear lower among patients who have DT; and (4) DT is associated with uncommon, but serious complications and adds cost and complexity to the ICD implant procedure. A large randomized evaluation of DT will soon be completed8; however, the observational data …

Underdetection of ventricular fibrillation despite ICD testing and high sinus R wave

Apart from monitoring shock efficacy, proof of flawless detection of induced ventricular fibrillation (VF) is a decisive argument in favor of implantable cardioverter defibrillator (ICD) testing. On the other hand, it has been observed that undersensing of VF is extremely rare with good sensing of the intrinsic R wave of ≥ 5-7mV. The case presented here shows limitations in both argumentations: Neither optimal R wave sensing during sinus rhythm nor repeated ICD testing could rule out or predict multiple erroneous detections of clinical VF episodes. This must be taken into consideration in the current discussion on the necessity of defibrillation testing. Further optimization of sensing technology should be a focus in the development of modern ICD systems so as to improve the safety and efficacy of ICD therapy.

How to Manage a High Defibrillation Threshold in ICD Patients: and Does it Really Matter?

In the 30years since its introduction, implantable cardioverter defibrillator (ICD) hardware and programming has evolved greatly. Coupled with a better understanding of how patient factors and anti-arrhythmic drug therapy affect ICD function, these changes have resulted in a modern ICD system which is highly effective at terminating ventricular arrhythmias. This has led to a marked decrease in the conduct of intraoperative defibrillation testing. Still, clinicians are faced with patients who have had unsuccessful intraoperative defibrillation testing or who have experienced one or more failed clinical shocks for ventricular arrhythmias. Thus, clinicians caring for ICD patients must understand the expected performance of modern ICD systems, understand the issues with intraoperative defibrillation testing, and have a strategy for dealing with patients when their ICD has failed to terminate a clinical or induced ventricular arrhythmia. This review will focus on the clinical approach to such patients, including trouble-shooting and system revision.

Defibrillation Threshold Testing: Who Doesn't Get It?

Defibrillation testing has been routinely performed as part of the implantable cardioverter-defibrillator (ICD) implantation procedure, and is currently supported by practice guidelines; however, more recently, this practice has been called into question. Such testing is safe, and serious complications are rare. With modern ICD systems, physicians will rarely encounter a patient in whom defibrillation will fail. This article reviews the literature regarding the utility, necessity, complications, and cost of routine operative and follow-up defibrillation testing, and, it is hoped, clarifies the issue of "Who doesn't get it?"

Implantable cardioverter-defibrillator longevity under clinical circumstances: An analysis according to device type, generation, and manufacturer

One of the major drawbacks of implantable cardioverter-defibrillator (ICD) treatment is the limited device service life. Thus far, data concerning ICD longevity under clinical circumstances are scarce. In this study, the ICD service life was assessed in a large cohort of ICD recipients. To assess the battery longevity of ICDs under clinical circumstances. All patients receiving an ICD in the Leiden University Medical Center were included in the analysis. During prospectively recorded follow-up visits, reasons for ICD replacement were assessed and categorized as battery depletion and non-battery depletion. Device longevity and battery longevity were calculated. The impact of device type, generation, manufacturer, the percentage of pacing, the pacing output, and the number of shocks on the battery longevity was assessed. Since 1996, 4673 ICDs were implanted, of which 1479 ICDs (33%) were replaced. Mean device longevity was 5.0 ± 0.1 years. A total of 1072 (72%) ICDs were replaced because of battery depletion. Mean battery longevity of an ICD was 5.5 ± 0.1 years. When divided into different types, mean battery longevity was 5.5 ± 0.2 years for single-chamber ICDs, 5.8 ± 0.1 for dual-chamber ICDs, and 4.7 ± 0.1 years for cardiac resynchronization therapy-defibrillators (P <.001). Devices implanted after 2002 had a significantly better battery longevity as compared with devices implanted before 2002 (5.6 ± 0.1 years vs 4.9 ± 0.2 years; P <.001). In addition, large differences in battery longevity between manufacturers were noted (overall log-rank test, P <.001). The majority of ICDs were replaced because of battery depletion. Large differences in longevity exist between different ICD types and manufacturers. Modern ICD generations demonstrated improved longevity.

Management of the Patient With Implantable Cardioverter-Defibrillator Lead Failure

52-year-old man was brought to the emergency department because of multiple implantable cardioverter-defibrillator (ICD) shocks. His existing dual-chamber pacemaker was upgraded from a biventricular ICD 4 years ago. The ECG in the emergency department showed sinus tachycardia with left bundle-branch block at a rate of 135 bpm. In the emergency department, the patient received 5 additional shocks without a change in rhythm. A donut magnet was placed over the ICD. Interrogation revealed evidence of a lead fracture, and tachycardia therapies were disabled. The high-voltage lead was a Medtronic Sprint Fidelis ICD lead. Admission to the hospital was recommended for definitive correction of his problem. This case illustrates the most common presentation of an ICD lead failure and the resulting management challenges. Lead failure is typically thought of as an intrinsic design or construction defect leading to an adverse clinical event. However, any adverse clinical event mediated through malfunction of an ICD lead represents lead failure. An ICD lead failure can occur in any patient, even with leads that have a proven record of reliability. The overall incidence of ICD lead failure is difficult to assess because of its underreporting and the absence of strict reporting requirements. Random component failures in individual patients are especially difficult to quantify, but some studies suggest a failure rate of ≈0.58%/y among modern ICD leads.1 Leads that have undergone manufacturer advisory or Food and Drug Administration alerts have a much higher incidence of failure. Examples of ICD leads with high failure rates include the Guidant Endotak DSP (model 0125) and the Medtronic Transvene (model 6936). The 6936 lead had a 90% survival rate at 4 to 5 years and a nearly 60% survival rate at 8 to 9 years. Therefore, lead failure rates are not linear over time. The recent recall of the Medtronic …

Ventricular oversensing due to manufacturer-related differences in implantable cardioverter-defibrillator signal processing and sensing lead properties

Ventricular oversensing remains a significant problem in modern implantable cardioverter-defibrillator (ICD) systems. The role of manufacturer-related differences in device-based signal processing on the one hand and sensing lead properties on the other is largely unknown. This retrospective study aimed to evaluate and compare the incidence and mechanisms of ventricular oversensing in single- or dual-chamber ICD systems from Biotronik (BTK), Guidant (GDT), and Medtronic (MDT). In 245 consecutive patients, device function, stored episodes, and lead parameters were evaluated at implant and during 243 ± 18 days of follow-up. Oversensing occurred in 3.3% of the patients [four T-wave oversensing (TWO), three R-wave double-sensing, and one diaphragmatic myopotentials]. The incidence of ventricular oversensing was generally low if an ICD device and an ICD lead were from one identical manufacturer (BTK: 2/68, GDT: 1/80, and MDT: 1/69; P = 0.67). In the subgroup of ICDs connected to leads from other manufacturers, however, ventricular oversensing was observed in none of 19 GDT and MDT ICDs but in 4 of 9 BTK devices (44.4%, P = 0.012). These four cases of oversensing (three R-wave double-sensing and one TWO) all occurred in BTK ICDs connected to integrated bipolar ICD leads from other manufacturers. Significant manufacturer-related differences exist in the incidence of ventricular oversensing in single- and dual-chamber ICD systems. Biotronik devices connected to integrated bipolar ICD leads from other manufacturers have an increased risk for R-wave double-sensing.

Defibrillation threshold testing: Is it necessary during implantable cardioverter-defibrillator implantation?

Defibrillation threshold (DFT) testing has traditionally been a routine part of implantable cardioverter-defibrillator (ICD) implantation. DFT testing was developed in the early days of the ICD when failure of defibrillation was common, recipients had a high-risk of ventricular tachycardia (VT) or ventricular fibrillation (VF), and the only therapy for rapid VT or VF was a shock. However, modern ICD systems have such a high rate of successful defibrillation that many electrophysiologists now question whether DFT testing is still worthwhile. Studies found that long-term mortality was not higher among patients not undergoing DFT testing. Moreover, there was no survival difference between patients with a lower DFT and a higher DFT. Other studies have demonstrated that DFT testing poses some risk to the patient such as myocardial damage, embolic stroke in patient with atrial fibrillation and DFT testing-related death. If DFT testing is abandoned, more patients may have the opportunity to be treated with ICD, especially in regions with few or no electrophysiologists. It may be argued that other physicians, such as those currently implanting pacemakers, would more readily implant ICDs if not for the requirement of DFT testing.

No Benefit From Defibrillation Threshold Testing in the SCD-HeFT (Sudden Cardiac Death in Heart Failure Trial)

This study investigated whether defibrillation threshold (DFT) testing during implantable cardioverter-defibrillator (ICD) implantation predicts clinical outcomes. Defibrillation testing is often performed during insertion of ICDs to confirm shock efficacy. There are no prospective data to suggest that this procedure improves outcomes when modern ICDs are implanted for primary prevention of sudden death. The analysis included the 811 patients who were randomized to the ICD arm of the SCD-HeFT (Sudden Cardiac Death in Heart Failure Trial) and had the device implanted. The DFT testing protocol in SCD-HeFT was designed to limit shock testing in a primary prevention heart failure population. Baseline DFT data were available for 717 patients (88.4%). All 717 patients had a DFT of < or =30 J, the maximum output of the device in this study. The DFT was < or =20 J in 97.8% of patients. There was no survival difference between patients with a lower DFT (< or =10 J, n = 547) and a higher DFT (>10 J, n = 170) (p = 0.41). First shock efficacy was 83.0% for the first clinical ventricular tachyarrhythmia event; there were no differences in shock efficacies when the cohort was subdivided by baseline DFT. Low baseline DFTs were obtained in patients with stable, optimally treated heart failure during ICD implantation for primary prevention of sudden death. First shock efficacy for ventricular tachyarrhythmias was high regardless of baseline DFT testing results. Baseline DFT testing did not predict long-term mortality or shock efficacy in this study.

Implantable Cardioverter-Defibrillator Lead Performance

Implantable cardioverter-defibrillators (ICDs) have revolutionized the treatment of patients at risk for sudden cardiac death. In the nearly 3 decades since the first human ICD implant,1 millions of devices have been implanted worldwide and innumerable lives have been saved. Successful resuscitation of a potentially lethal ventricular arrhythmia by an ICD system depends on successful arrhythmia detection and timely delivery of therapy. Both the ICD generator and the ICD lead are critical components of this system. The lead, in particular, is literally a lifeline whose purpose is to convey critical information about the heart’s rhythm to the ICD generator and, in turn, to deliver life-sustaining therapy when needed. Failure of an ICD lead may result in significant clinical events, including failure to pace, failure to defibrillate, inappropriate shocks, and even death. Article p 2727 ICD leads, like many medical technologies, have undergone a remarkable transformation. Epicardial leads, which necessitated a thoracotomy for lead placement, have given way to transvenous leads, which are easier to implant, less costly, and associated with decreased morbidity and mortality.2 Important advances in transvenous lead technology, such as the development of steroid elution, smaller diameter leads, novel insulations, and multipolar leads, have translated into meaningful clinical benefits for patients. Although modern ICD leads consist primarily of electrodes, conductors, insulation, and a fixation mechanism to attach the lead to the myocardium, lead design and performance vary from model to model. Indeed, monitoring of performance is critical not only to identify products with increased failure rates but also to provide physicians and patients with realistic expectations of device performance. In the current issue of Circulation , Eckstein et al add to our understanding of ICD lead performance.3 The investigators conducted a retrospective analysis of 1317 consecutive patients who received ICD systems (including 38 different ICD lead …