Clinical Efficacy and Safety of an Implantable Cardioverter-Defibrillator Lead with a Floating Atrial Sensing Dipole

Ventricular arrhythmia detection for contemporary Biotronik and Abbott implantable cardioverter defibrillators with markedly prolonged detection in Biotronik devices

BACKGROUND

Implantable cardioverter defibrillators (ICDs) are typically programed with both ventricular tachycardia (VT) and ventricular fibrillation (VF) treatment zones. Biotronik and Abbott ICDs do not increment the VT counter when the tachycardia accelerates to the VF zone, which could result in a prolonged delay in tachycardia detection.

METHODS

Patients with Biotronik and Abbott ICDs receiving care at Veterans Affairs facilities in Northern California were identified. Patient information and device tracings for patients with any ICD therapies were examined to assess for possible delayed tachycardia detection.

RESULTS

Among 52 patients with Biotronik ICDs, 8 (15%) experienced appropriate ICD therapy over a median follow-up of 29 months. Among 68 patients with Abbott ICDs, 26 (38%) experienced appropriate ICD therapy over a median follow-up of 83 months. Three of the patients with Biotronik ICDs who received appropriate therapy experienced a delay in VT/VF detection due to the tachycardia rate oscillating between the VT and VF treatment zones (longest 31.2 s on detection), compared with four of the patients with Abbott ICDs (longest 4.1 s on the detection and 8 s on redetect). One of the patients with a Biotronik ICD experienced recurrent syncope associated with delayed detection and another died on the day of delayed detection. One of the patients with an Abbott ICD experienced syncope.

CONCLUSIONS

Because contemporary Biotronik and Abbott ICDs freeze the VT counters when tachycardia is in the VF zone, ICD therapies can be markedly delayed when the tachycardia oscillates between the VT and VF zone.

Ability to remotely monitor atrial high-rate episodes using a single-chamber implantable cardioverter-defibrillator with a floating atrial sensing dipole

AIMS

To allow timely initiation of anticoagulation therapy for the prevention of stroke, the European guidelines on atrial fibrillation (AF) recommend remote monitoring (RM) of device-detected atrial high-rate episodes (AHREs) and progression of arrhythmia duration along pre-specified strata (6 min…<1 h, 1 h…<24 h, ≥ 24 h). We used the MATRIX registry data to assess the capability of a single-lead implantable cardioverter-defibrillator (ICD) with atrial sensing dipole (DX ICD system) to follow this recommendation in patients with standard indication for single-chamber ICD.

METHODS AND RESULTS

In 1841 DX ICD patients with daily automatic RM transmissions, electrograms of first device-detected AHREs per patient in each duration stratum were adjudicated, and the corresponding positive predictive values (PPVs) for the detections to be true atrial arrhythmia were calculated. Moreover, the incidence and progression of new-onset AF was assessed in 1451 patients with no AF history. A total of 610 AHREs ≥6 min were adjudicated. The PPV was 95.1% (271 of 285) for episodes 6min…<1 h, 99.6% (253/254) for episodes 1 h…<24 h, 100% (71/71) for episodes ≥24 h, or 97.5% for all episodes (595/610). The incidence of new-onset AF was 8.2% (119/1451), and in 31.1% of them (37/119), new-onset AF progressed to a higher duration stratum. Nearly 80% of new-onset AF patients had high CHA2DS2-VASc stroke risk, and 70% were not on anticoagulation therapy. Age was the only significant predictor of new-onset AF.

CONCLUSION

A 99.7% detection accuracy for AHRE ≥1 h in patients with DX ICD systems in combination with daily RM allows a reliable guideline-recommended screening for subclinical AF and monitoring of AF-duration progression.

The efficacy of single-lead implantable cardioverter-defibrillator with atrial sensing dipole to detect atrial fibrillation and to reduce inappropriate therapy according to atrial sensing ON or OFF: Rationale and design of the SMART-CONTROL study, a prospective multicenter randomized trial

BACKGROUND

Few studies have compared the efficacy of single-lead implantable cardioverter-defibrillator (ICD) with atrial sensing dipole (VDD-ICD) and conventional single-chamber ICD from the aspect of atrial fibrillation (AF) detection or inappropriate ICD therapy reduction. In the SMART-CONTROL trial (NCT03932604), we primarily aim to investigate whether the atrial sensing capability of VDD-ICD is useful in AF detection and inappropriate therapy reduction by randomly activating or deactivating the atrial sensing function.

METHODS AND DESIGN

This study was designed as a prospective, multicenter, open-label, randomized trial to enroll 640 patients with no history of clinical AF or rhythm control for AF within 1 year who were undergoing the implantation of VDD-ICD system. Patients are assigned randomly to atrial sensing "ON" or "OFF" group, with crossover allowed during follow-up. The coprimary outcomes are the incidence of AF detection and inappropriate ICD therapy over a 2-year follow-up period. The secondary outcomes include non-AF atrial tachyarrhythmia, ventricular tachyarrhythmia with or without ICD therapy, thromboembolic events, bleeding, heart failure hospitalization, mortality, a composite of adverse cardiovascular events, and long-term atrial sensing stability or variability.

CONCLUSION

We expect that this trial can evaluate the efficacy of a single-lead ICD system on various clinical outcomes including AF detection and inappropriate therapy reduction, and ultimately provide guidance to selection of ICD system.

The utilization of atrial sensing dipole in single lead implantable cardioverter defibrillator for detection of new-onset atrial high-rate episodes or subclinical atrial fibrillation: A systematic review and meta-analysis

This meta-analysis aims to evaluate the performance of atrial sensing dipole in single lead implantable cardioverter defibrillator (VDD-ICD) recipients in particular diagnosing new-onset atrial high-rate episodes (AHREs) defined as rate threshold of 200 beats per minute, or subclinical atrial fibrillation (SCAF) defined as device-detected AF without symptoms. We comprehensively searched PubMed, Embase, and ClinicalTrials.gov. Studies comparing contemporary single- and dual-chamber ICD (VVI-/DDD-ICD) versus VDD-ICD were included. Restricted maximum likelihood method for random effect model and Mantel-Haenszel method for fixed effect model were used to estimate the effect size of new-onset AHREs, or SCAF detection in each group. Three prospective studies were identified and total of 991 participants were included. There were 330 (33.3%) in VDD-ICD and 661 (66.7%) in VVI-/DDD-ICD. Most (78%) participants were men. Median follow-up was from 365 days to 847 days. VDD-ICD has a higher likelihood of detecting AHREs or SCAF as compared to VVI-/DDD-ICD [(OR random effect : 2.6; 95% CI: 1.2, 5.8; p = .018); I-squared = 67.8%, p = .019]. This difference was more apparently seen in the comparison between VDD-ICD and VVI-ICD [(OR random effect: 3.8; 95% CI: 2.1, 6.6, p < .001), I-squared = 0.0%, p = .518]. The result is same as fixed effect. Rate of AHREs detection observed in VDD-ICD was not statistically different when compared to the only group with DDD-ICD from SENSE trial. In conclusion, this meta-analysis reveals that the use of floating atrial sensing dipole in VDD-ICD increases the detection of new-onset AHREs or SCAF when compared to VVI-ICD, with similar atrial sensing performance to DDD-ICD.

Long-term evaluation of sensing variability of a floating atrial dipole in a single‑lead defibrillator: The mechanistic basis of long-term stability of amplified atrial electrogram

BACKGROUND

A single‑lead implantable cardioverter-defibrillator (ICD) with a floating atrial dipole has been developed to enhance the diagnostic capability of atrial arrhythmias and to facilitate adjudication of arrhythmic events without the additional effort required for atrial lead insertion. However, there have been concerns about the long-term reliability of atrial sensing.

METHODS

We enrolled patients with the single-chamber ICD with atrial-sensing electrodes from 4 tertiary university hospitals in Korea. Minimal, maximal, and mean P wave amplitudes were collected at 3-6 months, 6-12 months, and 12-24 months after implantation. The difference between the minimal and maximal sensing amplitudes was calculated as an indicator of the variability of atrial sensing, while the atrial sensing stability was assessed using the mean amplitude.

RESULTS

A total of 86 patients were included for analysis. The variability of atrial sensing amplitudes significantly decreased at 12-24 months compared to 3-6 months (p = 0.01), while mean atrial amplitudes were stable throughout the mean follow-up duration of 17.4 months. Nine patients (10.5%) experienced inappropriate ICD therapy mostly due to misclassification of supraventricular tachycardia.

CONCLUSIONS

Under the hypothesis that sensing stability can be guaranteed as the variability decreases with time, we suggest that the concern about long-term sensing stability of a floating dipole can be abated with an ICD that has been implanted for over 2 years.

Rationale and feasibility of the atrioventricular single-lead ICD systems with a floating atrial dipole (DX) in clinical practice

Cardiac implantable electronic devices establish proper therapy for the prevention of sudden cardiac death, significantly reducing the morbidity and mortality of patients with arrhythmias and heart failure. It is well-known that the number of electrodes increases the risk of complications. To preserve the benefit of atrial sensing without the need to implant an additional lead, a single-lead ICD system with a floating atrial dipole (DX ICD lead) has been developed. Besides all of the potential benefits, the necessity of a reliable and stable atrial sensing via the floating dipole could be the main concern against the use of this lead type. In the current generation of DX devices, the specially filtered atrial signal seems to be high enough and stable over time, which is crucial in the early detection of atrial arrhythmias, discrimination between different forms of tachycardias in order to prevent inappropriate ICD therapy, and achieving an optimal atrioventricular and interventricular synchrony in patients with a two-lead CRT-DX system. The present review summarizes the benefits and potential drawbacks of the DX ICD systems based on the available literature, furthermore, proposes an evidence-based algorithm of ICD type selection.

Real-world performance of the atrial fibrillation monitor in patients with a subcutaneous ICD

Introduction

The third‐generation subcutaneous implantable cardioverter‐defibrillator (S‐ICD) (EMBLEM™ A219, Boston Scientific) contains a new diagnostic tool to detect atrial fibrillation (AF) in S‐ICD patients, without the use of an intracardiac lead. This is the first study to evaluate the performance of the S‐ICD AF monitor (AFM).

Methods

The AFM algorithm analyzes a subcutaneous signal for the presence of AF, similar to the signals collected by implantable and wearable diagnostic devices. The AFM algorithm combines heart rate (HR) scatter analysis with an HR histogram. The algorithm was tested against publicly available electrocardiogram databases (simulated performance). Real‐world performance of the algorithm was evaluated by using the S‐ICD LATITUDE remote monitoring (RM) database.

Results

The simulated performance of the AFM algorithm resulted in a sensitivity of 95.0%, specificity of 100.0%, and positive predictive value (PPV) of 100.0%. To evaluate the real‐world performance of the AFM, 7744 S‐ICD devices were followed for up to 30 months by RM, whereof 99.5% had the AFM enabled. A total of 387 AF episodes were randomly chosen for adjudication, resulting in a PPV of 67.7%. The main cause of misclassification was atrial and ventricular ectopy.

Conclusion

The AFM exhibited a very high sensitivity and specificity in a simulated setting, designed to maximize PPV in order to minimize the clinical burden of reviewing falsely detected AF events. The real‐world performance of the AFM, enabled in 99.5% of S‐ICD patients, is a PPV of 67.7%.

The efficacy of the LinoxSmart DX ICD lead from a single center experience

Purpose

The Biotronik Linox^Smart DX implanted cardioverter defibrillator (ICD) lead is a novel VDD lead with the advantage of integrated atrial sensing dipole combined with a special augmentation and filtering mechanisms. We sought to determine the efficacy of the Biotronik Linox^Smart DX ICD lead.

Methods

Non-randomized consecutive patients implanted with Biotronik Linox^Smart DX lead at Sheba Medical Center were included in this study. Electrical parameters and arrhythmic events were recorded during follow up of one year.

Results

Seventy-three patients (69 males (94.5%), mean age 61 ± 12 years) were included. All patients were successfully implanted with a Biotronic VR-T DX device and Linox^Smart DX ICD lead (DX-17 in 37% and DX-15 in 63% patients). Mean P wave amplitude at time of implantation was 3.66 ± 2.9 mV and improved significantly throughout the follow-up (5.29 ± 4.39 mV, p = 0.009). Appropriate atrial sensing (defined as P wave amplitude of ≥0.8 mV) rate of 100% at implantation significantly decreased to 89% (p = 0.015) at 12 months. Three out of 67 (4.5%) patients without a known history of atrial fibrillation had documented new onset paroxysmal atrial fibrillation. Appropriate shocks occurred in 4 (5.5%) patients. One patient with atrial sensing less than 0.4 mV had inappropriate shock.

Conclusions

Among patients implanted with the Biotronik Linox^Smart DX ICD lead in our single center, appropriate atrial sensing rate decreased over 12 months. Larger studies are needed to evaluate the reliability of long term appropriate atrial sensing.

Subclinical atrial fibrillation detection with a floating atrial sensing dipole in single lead implantable cardioverter-defibrillator systems: Results of the SENSE trial

INTRODUCTION

Subclinical atrial fibrillation (AF), in the form of cardiac implantable device-detected atrial high rate episodes (AHREs), has been associated with increased thromboembolism. An implantable cardioverter-defibrillator (ICD) lead with a floating atrial dipole may permit a single lead (DX) ICD system to detect AHREs. We sought to assess the utility of the DX ICD system for subclinical AF detection in patients, with a prospective multicenter, cohort-controlled trial.

METHODS AND RESULTS

One hundred fifty patients without prior history of AF (age 59 ± 13 years; 108 [72%] male) were enrolled into the DX cohort and implanted with a Biotronik DX ICD system at eight centers. Age-, sex-, and left ventricular ejection fraction-matched single- and dual-chamber ICD cohorts were derived from a Cornell database and from the IMPACT trial, respectively. The primary endpoint were AHRE detection at 12 months. During median 12 months follow-up, AHREs were detected in 19 (13%) patients in the DX, 8 (5.3%) in the single-chamber, and 19 (13%) in the dual-chamber cohorts. The rate of AHRE detection was significantly higher in the DX cohort compared to the single-chamber cohort (P = .026), but not significantly different compared to the dual-chamber cohort. There were no inappropriate ICD therapies in the DX cohort. At 12 months, only 3.0% of patients in the DX cohort had sensed atrial amplitudes less than 1.0 mV.

CONCLUSION

Use of a DX ICD lead allows subclinical AF detection with a single lead DX system that is superior to that of a conventional single-chamber ICD system.

Cost Saving Potential of an Early Detection of Atrial Fibrillation in Patients after ICD Implantation

Atrial fibrillation (AF) is a relevant comorbidity in recipients of implantable cardioverter-defibrillators (ICD). Latest generation single-chamber ICD allow the additional sensing of atrial tachyarrhythmias and, therefore, contribute to the early detection and treatment of AF, potentially preventing AF-related stroke. The present study aimed to measure the impact on patient-related costs of this new ICD compared to conventional ICD. A Markov model was developed to simulate the long-term incidence of stroke in patients treated with a single-chamber ICD with or without atrial sensing capabilities. The median annual cost per patient and its difference, the number of strokes avoided, and the cost per stroke avoided were estimated. During a 9-year horizon, the costs for the ICD and stroke treatment were €570 per patient-year for an ICD with atrial sensing capabilities and €491 per patient-year for a conventional ICD. Per 1,000 patients, 4.6 strokes per year are assumed to be avoided by the new device. Higher CHA2DS2-VASc scores are associated with higher numbers of avoided strokes and larger potential for cost savings. Apart from clinical advantages, the use of ICD with atrial sensing capabilities may reduce the incidence of stroke and, in high-risk patients, may also contribute to reduce overall health care costs.

Atrial electrogram quality in single-pass defibrillator leads with floating atrial bipole in patients with permanent atrial fibrillation and cardiac resynchronization therapy

Many patients receiving cardiac resynchronization therapy (CRT) suffer from permanent atrial fibrillation (AF). Knowledge of the atrial rhythm is important to direct pharmacological or interventional treatment as well as maintaining AV-synchronous biventricular pacing if sinus rhythm can be restored. A single pass single-coil defibrillator lead with a floating atrial bipole has been shown to obtain reliable information about the atrial rhythm but has never been employed in a CRT-system. The purpose of this study was to assess the feasibility of implanting a single coil right ventricular ICD lead with a floating atrial bipole and the signal quality of atrial electrograms (AEGM) in CRT-defibrillator recipients with permanent AF.

Methods and results

Seventeen patients (16 males, mean age 73 ± 6 years, mean EF 25 ± 5%) with permanent AF and an indication for CRT-defibrillator placement were implanted with a designated CRT-D system comprising a single pass defibrillator lead with a atrial floating bipole. They were followed-up for 103 ± 22 days using remote monitoring for AEGM transmission. All patients had at last one AEGM suitable for atrial rhythm diagnosis and of 100 AEGM 99% were suitable for visual atrial rhythm assessment. Four patients were discharged in sinus rhythm and one reverted to AF during follow-up.

Conclusion

Atrial electrograms retrieved from a single-pass defibrillator lead with a floating atrial bipole can be reliably used for atrial rhythm diagnosis in CRT recipients with permanent AF. Hence, a single pass ventricular defibrillator lead with a floating bipole can be considered in this population.

ICD discrimination of SVT versus VT with 1:1 V-A conduction: A review of the literature

Inappropriate ICD shocks are associated with increased mortality. They also impair patients' quality of life, increase hospitalizations, and raise health-care costs. Nearly 80% of inappropriate ICD shocks are caused by supraventricular tachycardia. Here we report the case of a patient who received a single-lead dual-chamber sensing ICD for primary prevention of sudden cardiac death and experienced inappropriate ICD shocks. V-A time, electrogram morphology, and response to antitachycardia pacing suggested atrioventricular nodal reentry tachycardia, which was confirmed in an electrophysiology study. Inspired by this case, we performed a literature review to discuss mechanisms for discrimination of supraventricular tachycardia with 1:1 A:V relationship from ventricular tachycardia with 1:1 retrograde conduction.

"Two for the Price of One": A Single-Lead Implantable Cardioverter-Defibrillator System with a Floating Atrial Dipole

In patients known to be a high risk for sudden cardiac arrest, implantable cardioverter defibrillators (ICD) are a proven therapy to reduce risk of death. However, in patients without conventional indications for pacing, the optimal strategy for type of device, dual- versus single-chamber, remains debatable. The benefit of prophylactic pacing in this category of patients has never been documented. Although available atrial electrograms in a dual chamber system improve interpretation of stored arrhythmia events, allow monitoring of atrial fibrillation and may potentially reduce the risk of inappropriate shocks by enhancing automated arrhythmia discrimination, the use of dual-chamber ICDs has a number of disadvantages. The addition of an atrial lead adds complexity to implantation and extraction procedures, increases procedural cost and is associated with a higher risk of periprocedural complications. The single lead pacing system with ability to sense atrial signals via floating atrial electrodes (VDD) clinically became available in early 1980's but did not gain much popularity due to inconsistent atrial sensing and concerns about the potential need for an atrial lead if sinus node fails. Most ICD patients do not have indications for pacing at implantation and subsequent risk of symptomatic bradycardia seems to be low. The concept of atrial sensing via floating electrodes has recently been revitalized in the Biotronik DX ICD system (Biotronik, SE & Co., Berlin, Germany) aiming to provide all of the potential advantages of available atrial electrograms without the risks and incremental cost of an additional atrial lead. Compared to a traditional VDD pacing system, the DX ICD system uses an optimized (15 mm) atrial dipole spacing and improved atrial signal processing to offer more reliable atrial sensing. The initial experience with the DX system indicates that the clinically useful atrial signal amplitude in sinus rhythm remains stable over time. Future studies are needed to determine reliability of atrial sensing during tachyarrhythmias, particularly atrial fibrillation as well as clinical utility and cost-effectiveness of this technology in different populations of patients.

Implantable cardioverter defibrillator system with floating atrial sensing dipole: a single-center experience

BACKGROUND

The concept of a single-lead dual-chamber implantable cardioverter defibrillator (ICD) with floating sensing atrial dipole has been proven safe and functional. We report a single-center experience with this ICD system; the major focus of the work is on the recorded atrial activation and its stability on a medium term follow-up.

METHODS

Thirteen patients received a DX ICD (BIOTRONIK SE & Co, Berlin, Germany) with the Linox Smart S DX(ProMRI) ICD lead; the implantation data were reported. Daily P- and R-wave sensing amplitude was collected and followed up during 200 days; their coefficient of variance (CV) was calculated. In addition, all the atrial and ventricular high-rate episodes were analyzed.

RESULTS

The total x-ray exposure time was 3.9 ± 1.8 minutes. The overall mean sensing was 4.2 ± 1.9 mV for P wave and 12.9 ± 4.5 mV for R wave. The CV was significantly higher for the P-wave amplitude than for the R-wave one (0.25 ± 0.11 vs 0.08 ± 0.06; P < 0.001). A total of 27 high ventricular rate episodes were recorded and correctly discriminated by the device. Fifty-six high atrial rate episodes were recorded, 49 were true arrhythmic events.

CONCLUSIONS

The single-lead ICD system with floating atrial dipole provides reliable atrial sensing amplitude over time. The physician, without the implantation of an additional lead, has the atrial information that may be used for the discrimination of supraventricular tachyarrhythmia/ventricular tachycardia, for the early detection of atrial fibrillation episodes and for the evaluation of changes in the patient's heart status.