Prospective randomized multicenter trial of empirical antitachycardia pacing versus shocks for spontaneous rapid ventricular tachycardia in patients with implantable cardioverter-defibrillators: Pacing Fast Ventricular Tachycardia Reduces Shock Therapies (PainFREE Rx II) trial results

Lead Management: Device Programming and Defibrillation Threshold Testing

Implantable cardioverter-defibrillators (ICDs) reduce sudden cardiac death (SCD) and improve survival in patients with a history of life-threatening arrhythmia or sudden cardiac arrest, and in select populations at high risk of SCD due to ventricular arrhythmias. However, patients with ICDs may receive inappropriate or unnecessary shocks, which have been associated with pro-arrhythmia, psychological sequelae, poor quality of life, and increased mortality. The benefits and risks of ICD therapy are therefore directly impacted on by physician operative and programming decisions. This article aims to provide a detailed review of transvenous ICD programming as guided by clinical trials.

A Modular Communicative Leadless Pacing-Defibrillator System

BACKGROUND

The subcutaneous implantable cardioverter-defibrillator (ICD) is associated with fewer lead-related complications than a transvenous ICD; however, the subcutaneous ICD cannot provide bradycardia and antitachycardia pacing. Whether a modular pacing-defibrillator system comprising a leadless pacemaker in wireless communication with a subcutaneous ICD to provide antitachycardia and bradycardia pacing is safe remains unknown.

METHODS

We conducted a multinational, single-group study that enrolled patients at risk for sudden death from ventricular arrhythmias and followed them for 6 months after implantation of a modular pacemaker-defibrillator system. The safety end point was freedom from leadless pacemaker-related major complications, evaluated against a performance goal of 86%. The two primary performance end points were successful communication between the pacemaker and the ICD (performance goal, 88%) and a pacing threshold of up to 2.0 V at a 0.4-msec pulse width (performance goal, 80%).

RESULTS

We enrolled 293 patients, 162 of whom were in the 6-month end-point cohort and 151 of whom completed the 6-month follow-up period. The mean age of the patients was 60 years, 16.7% were women, and the mean (±SD) left ventricular ejection fraction was 33.1±12.6%. The percentage of patients who were free from leadless pacemaker-related major complications was 97.5%, which exceeded the prespecified performance goal. Wireless-device communication was successful in 98.8% of communication tests, which exceeded the prespecified goal. Of 151 patients, 147 (97.4%) had pacing thresholds of 2.0 V or less, which exceeded the prespecified goal. The percentage of episodes of arrhythmia that were successfully terminated by antitachycardia pacing was 61.3%, and there were no episodes for which antitachycardia pacing was not delivered owing to communication failure. Of 162 patients, 8 died (4.9%); none of the deaths were deemed to be related to arrhythmias or the implantation procedure.

CONCLUSIONS

The leadless pacemaker in wireless communication with a subcutaneous ICD exceeded performance goals for freedom from major complications related to the leadless pacemaker, for communication between the leadless pacemaker and subcutaneous ICD, and for the percentage of patients with a pacing threshold up to 2.0 V at a 0.4-msec pulse width at 6 months. (Funded by Boston Scientific; MODULAR ATP ClinicalTrials.gov NCT04798768.).

Decision-making regarding subcutaneous implantable cardioverter defibrillator as primary prevention in patients with low ejection fraction

BACKGROUND

Conventional transvenous implantable cardioverter-defibrillator (TV-ICD) is the standard device used for primary prevention of sudden cardiac death (SCD) in patients with reduced left ventricular ejection fraction (LVEF). Nonetheless its use is associated with lead-related complications including infection and malfunction. A subcutaneous implantable cardioverter-defibrillator (S-ICD) offers an alternative option without the need for a transvenous lead but has limitations. The decision to implant a TV-ICD or S-ICD in patients with impaired LVEF for primary prevention of SCD is controversial. Several randomised controlled trials and large observational studies have confirmed similar safety and efficacy of S-ICDs and TV-ICDs in such population.

METHODS

A literature review was conducted to compare the outcomes of subcutaneous (S-ICD) versus transvenous (TV-ICD) implantable cardioverter-defibrillators. Databases including PubMed, MEDLINE, and Cochrane were searched for relevant peer-reviewed articles. Studies were selected based on relevance and quality. Key outcomes like complication rates, efficacy, and patient survival were summarized in a comparative table.

RESULTS

Different factors that influence the choice between an TV-ICD and S-ICD for primary prevention of SCD in patients with LVEF are highlighted to guide selection of the appropriate device in different patient populations. Moreover, future perspective on the combination of SICD with leadless pacemaker, and the latest development of the extravascular implantable cardioverter defibrillator are also discussed.

CONCLUSIONS

S-ICD offers a safe and efficacious option to primary prevention in reduced ejection fraction. Future development including incorporation of leadless pacemaker will add to the arsenal of choice to protect patients from sudden cardiac death.

A randomized clinical trial of catheter ablation and antiarrhythmic drug therapy for suppression of ventricular tachycardia in ischemic cardiomyopathy: The VANISH2 trial

BACKGROUND

Recurrent ventricular tachycardia (VT) in patients with prior myocardial infarction is associated with adverse quality of life and clinical outcomes, despite the presence of implanted defibrillators (ICDs). Suppression of recurrent VT can be accomplished with antiarrhythmic drug therapy or catheter ablation. The Ventricular Tachycardia Antiarrhythmics or Ablation In Structural Heart Disease 2 (VANISH2) trial is designed to determine whether ablation is superior to antiarrhythmic drug therapy as first line therapy for patients with ischemic cardiomyopathy and VT.

METHODS

The VANISH2 trial enrolls patients with prior myocardial infarction and VT (with one of: ≥1 ICD shock; ≥3 episodes treated with antitachycardia pacing (ATP) and symptoms; ≥5 episodes treated with ATP regardless of symptoms; ≥3 episodes within 24 hours; or sustained VT treated with electrical cardioversion or pharmacologic conversion). Enrolled patients are classified as either sotalol-eligible, or amiodarone-eligible, and then are randomized to either catheter ablation or to that antiarrhythmic drug therapy, with randomization stratified by drug-eligibility group. Drug therapy, catheter ablation procedures and ICD programming are standardized. All patients will be followed until two years after randomization. The primary endpoint is a composite of mortality at any time, appropriate ICD shock after 14 days, VT storm after 14 days, and treated sustained VT below detection of the ICD after 14 days. The outcomes will be analyzed according to the intention-to-treat principle using survival analysis techniques RESULTS: The results of the VANISH2 trial are intended to provide data to support clinical decisions on how to suppress VT for patients with prior myocardial infarction.

CLINICALTRIALS

gov registration NCT02830360.

A His bundle pacing protocol for suppressing ventricular arrhythmia maintenance and improving defibrillation efficacy

BACKGROUND

The excitable gap (EG), defined as the excitable tissue between two subsequent wavefronts of depolarization, is critical for maintaining reentry that underlies deadly ventricular arrhythmias. EG in the His-Purkinje Network (HPN) plays an important role in the maintenance of electrical wave reentry that underlies these arrhythmias.

OBJECTIVE

To determine if rapid His bundle pacing (HBP) during reentry reduces the amount of EG in the HPN and ventricular myocardium to suppress reentry maintenance and/or improve defibrillation efficacy.

METHODS

In a virtual human biventricular model, reentry was initiated with rapid line pacing followed by HBP delivered for 3, 6, or 9 s at pacing cycle lengths (PCLs) ranging from 10 to 300 ms (n=30). EG was calculated independently for the HPN and myocardium over each PCL. Defibrillation efficacy was assessed for each PCL by stimulating myocardial surface EG with delays ranging from 0.25 to 9 s (increments of 0.25 s, n=36) after the start of HBP. Defibrillation was successful if reentry terminated within 1 s after EG stimulation. This defibrillation protocol was repeated without HBP. To test the approach under different pathological conditions, all protocols were repeated in the model with right (RBBB) or left (LBBB) bundle branch block.

RESULTS

Compared to without pacing, HBP for >3 seconds reduced average EG in the HPN and myocardium across a broad range of PCLs for the default, RBBB, and LBBB models. HBP >6 seconds terminated reentrant arrhythmia by converting HPN activation to a sinus rhythm behavior in the default (6/30 PCLs) and RBBB (7/30 PCLs) models. Myocardial EG stimulation during HBP increased the number of successful defibrillation attempts by 3%-19% for 30/30 PCLs in the default model, 3%-6% for 14/30 PCLs in the RBBB model, and 3%-11% for 27/30 PCLs in the LBBB model.

CONCLUSION

HBP can reduce the amount of excitable gap and suppress reentry maintenance in the HPN and myocardium. HBP can also improve the efficacy of low-energy defibrillation approaches targeting excitable myocardium. HBP during reentrant arrhythmias is a promising anti-arrhythmic and defibrillation strategy.

Computational modeling of cardiac electrophysiology and arrhythmogenesis: toward clinical translation

The complexity of cardiac electrophysiology, involving dynamic changes in numerous components across multiple spatial (from ion channel to organ) and temporal (from milliseconds to days) scales, makes an intuitive or empirical analysis of cardiac arrhythmogenesis challenging. Multiscale mechanistic computational models of cardiac electrophysiology provide precise control over individual parameters, and their reproducibility enables a thorough assessment of arrhythmia mechanisms. This review provides a comprehensive analysis of models of cardiac electrophysiology and arrhythmias, from the single cell to the organ level, and how they can be leveraged to better understand rhythm disorders in cardiac disease and to improve heart patient care. Key issues related to model development based on experimental data are discussed, and major families of human cardiomyocyte models and their applications are highlighted. An overview of organ-level computational modeling of cardiac electrophysiology and its clinical applications in personalized arrhythmia risk assessment and patient-specific therapy of atrial and ventricular arrhythmias is provided. The advancements presented here highlight how patient-specific computational models of the heart reconstructed from patient data have achieved success in predicting risk of sudden cardiac death and guiding optimal treatments of heart rhythm disorders. Finally, an outlook toward potential future advances, including the combination of mechanistic modeling and machine learning/artificial intelligence, is provided. As the field of cardiology is embarking on a journey toward precision medicine, personalized modeling of the heart is expected to become a key technology to guide pharmaceutical therapy, deployment of devices, and surgical interventions.

Comparison of novel intrinsic versus conventional antitachycardia pacing for ventricular tachycardia among implantable cardioverter-defibrillator recipients

INTRODUCTION

Intrinsic antitachycardia pacing (iATP) is a novel automated antitachycardia pacing (ATP) that provides individual treatment to terminate ventricular tachycardia (VT). However, the clinical efficacy of iATP in comparison with conventional ATP is unknown. We aim to compare the termination rate of VT between iATP and conventional ATP in patients with implantable cardioverter-defibrillators using a unique setting of different sequential orders of both ATP algorisms.

METHODS

Patients with the iATP algorithm were assigned to iATP-first and conventional ATP-first groups sequentially. In the iATP-first group, a maximum of seven iATP sequences were delivered, followed by conventional burst and ramp pacing. In contrast, in the conventional ATP-first group, two bursts and ramp pacing were initially programmed, followed by iATP sequences. We compared the success rates of VT termination in the first and secondary programmed ATP zones between the two groups.

RESULTS

Fifty-eight and 56 patients were enrolled in the iATP-first and conventional ATP-first groups, and 67 and 44 VTs were analyzed in each group, respectively. At the first single ATP therapy, success rates were 64% and 70% in the iATP and conventional groups, respectively. At the end of the first iATP treatment zone, the success rate increased from 64% to 85%. Moreover, secondary iATP therapy following the failure of conventional ATPs increased the success rate from 80% to 93%. There was a significant benefit of alternative iATP for VT termination compared to secondary conventional ATP (100% vs. 33%, p = .028).

CONCLUSIONS

iATP may be beneficial as a secondary therapy after failure of conventional ATP to terminate VT.

Left bundle branch pacing lead for sensing ventricular arrhythmias in implantable cardioverter-defibrillator: A pilot study (LBBP-ICD study)

BACKGROUND

Left bundle branch pacing (LBBP) has been suggested as an alternative modality for biventricular pacing in cardiac resynchronization therapy (CRT)-eligible patients. As it provides stable R-wave sensing, LBBP has been recently used to provide sensing of ventricular arrhythmia in patients receiving implantable cardioverter-defibrillator (ICD) with CRT.

OBJECTIVE

The aim of this study was to analyze the long-term safety and efficacy of the LBBP lead for appropriate detection of ventricular arrhythmia and delivery of antitachycardia pacing (ATP) in patients requiring defibrillator therapy with CRT.

METHODS

CRT-eligible patients who underwent successful LBBP-optimized ICD and LBBP-optimized CRT with defibrillator were enrolled. The LBBP lead was connected to the right ventricular-P/S port after capping the IS-1 connector plug of the DF-1-ICD lead. LBBP-optimized ICD or LBBP-optimized CRT with defibrillator was decided on the basis of correction of conduction system disease. Documented arrhythmic episodes and therapy delivered were analyzed.

RESULTS

Thirty patients were enrolled. The mean age was 59.7 ± 10.5 years. LBBP resulted in an increase in left ventricular ejection fraction from 29.9% ± 4.6% to 43.9% ± 11.2% (P < .0001). During a mean follow-up of 22.9 ± 12.5 months, 254 ventricular arrhythmic events were documented. Appropriate events (n = 225 [89%]) included nonsustained ventricular tachycardia (VT) (n = 212 episodes [94%]), VT (n = 8 [3.5%]), and ventricular fibrillation (n = 5 [2.5%]). ATP efficacy in terminating VT was 75%. Eleven percent of episodes (n = 29) were inappropriately detected because of T-wave oversensing. Inappropriate therapy (ATP) was delivered for 14 episodes (5.5%). Three patients (10%) had worsening of tricuspid regurgitation.

CONCLUSION

Sensing from the LBBP lead for arrhythmia detection is safe as ∼90% of the episodes were detected appropriately. Future studies with a dedicated LBBP-defibrillator lead along with algorithms to avoid oversensing can help in combining defibrillation with conduction system pacing.

[History of the implantable cardioverter-defibrillator in Germany]

The implantable cardioverter-defibrillator (ICD) was a breakthrough in the prevention of sudden cardiac death. After years of technical development in the USA, Michel Mirowski succeeded in proving reliable automatic defibrillation of ventricular tachyarrhythmias through initial human implantations in 1980, despite many obstacles. Nearly 4 years later, the first patients received ICDs at multiple centers in Germany. Subsequently, outside the USA, Germany became the country with highest implantation rates. The absolute number of implantations remained small as long as implantations required epicardial defibrillation electrodes and therefore thoracotomy by cardiac surgeons. Pacemaker-like implantation using a transvenous defibrillation electrode with a pectoral ICD became feasible in the early 1990s pushing implantation rates to the next level. Technical advancements were accompanied by clinical research in Germany, and often, the first-in-human studies were conducted in Germany. In 1991, the first guidelines for indications were established in the USA and Germany. Several randomized studies on indications were published between 1996 and 2009, mostly led by American teams with German participation, but also under German leadership (CASH, CAT, DINAMIT, IRIS). The DANISH study in 2016 questioned the results of these long-standing studies. Instead of providing ICDs to patients using a broad indication, future efforts aim to identify patients who, despite optimal medical therapy, cardiac resynchronization therapy (CRT), and/or catheter ablation, need protection against sudden cardiac death. Risk scores incorporating myocardial scars in magnetic resonance imaging (MRI) and genetic information are expected to contribute to more individualized and effective indications.

Evaluation of MADIT-II Risk Stratification Score Among Nationwide Registry of Heart Failure Patients With Primary Prevention Implantable Cardiac Defibrillators or Resynchronization Therapy Devices

The current guidelines advocate prophylactic implantable cardioverter-defibrillator (ICD) for all patients with symptomatic heart failure (HF) with low left ventricular ejection fraction. Because many patients will never use their device, a score delineating subgroups with differential ICD benefit is crucial. We aimed to evaluate the MADIT-II-based Risk Stratification Score (MRSS) feasibility to delineate the ICD survival benefit in a nationwide registry of patients with HF with prophylactic ICDs. Accordingly, all Israeli patients with HF with prophylactic ICD/cardiac resynchronization therapy defibrillators were categorized into MRSS-based risk subgroups. The study end points included overall mortality, sustained ventricular arrhythmia (VA), and a competing risk of VA (potential preventable arrhythmic death, where ICD could benefit survival) versus nonarrhythmic death. Potential ICD survival benefit was estimated by the area between these cumulative incidence curves. In 2,177 patients with HF implanted prophylactic device, 189 patients (8.7%) had VA and 316 (14.5%) died during a median follow-up of 2.9 years. The MRSS risk subgroups were significantly associated with overall mortality (p <0.001) and weakly with VA (p = 0.3). The competing risk analysis of VA versus nonarrhythmic death revealed a significantly shorter duration (p <0.001) and smaller magnitude of ICD survival benefit with increased risk subgroups, yielding an estimated 76, 60, 38, and 0 life days gained from prophylactic ICD implant during a 5-year follow-up for the MRSS low-, intermediate-, high-, and very high-risk subgroups, respectively (p for trend <0.05). In conclusion, MRSS use in a nationwide registry of patients with ischemic and nonischemic cardiomyopathy, revealed subgroups with differing ICD survival benefit, suggesting it could help evaluate prophylactic ICD survival benefit.

Canine Model of Ischemia-Induced Ventricular Tachycardia

INTRODUCTION

Despite advances in antiarrhythmia therapies, ventricular tachycardia (VT) is a leading cause of sudden cardiac death. Investigation into the characteristics and new treatments for this arrhythmia is required to improve outcomes and a reproducible model of VT would be useful in these endeavors. We therefore created a canine model of ischemia-induced VT.

MATERIALS AND METHODS

A pacing lead was implanted in the right ventricle in canines (n = 13) and the left anterior descending artery was occluded in two locations for 2 h and subsequently released to create an ischemia-reperfusion injury. In the 10 dogs that survived the first 48 h following the initial study, a terminal study was conducted 4-7 d later and VT was induced using premature stimulation or burst pacing through the right ventricle lead. The arrhythmia was terminated using either antitachycardia pacing or a defibrillatory shock. Multiple inductions into sustained VT were attempted.

RESULTS

Sustained VT was induced in eight of 10 dogs with an average cycle length of 335 ± 70 bpm. Multiple episodes of VT were induced. Episodes of VT exhibited different electrocardiogram morphologies and cycle lengths in individual animals.

CONCLUSIONS

This canine model provides a consistent technique for inducing multiple episodes of sustained VT. It may be useful for investigating VT mechanisms and testing novel therapeutics and treatments for patients with VT.

Transvenous versus subcutaneous implantable cardioverter defibrillators in young cardiac arrest survivors

Secondary prevention implantable cardioverter defibrillators (ICDs) are indicated in young patients presenting with aborted sudden cardiac death (SCD) because of ventricular arrhythmias. Transvenous-ICDs (TV-ICDs) are effective, established therapies supported by evidence. The significant morbidity associated with transvenous leads led to the development of the newer subcutaneous-ICD (S-ICD). This review discusses the clinical considerations when selecting an ICD for the young patient presenting with out-of-hospital cardiac arrest. The major benefits of TV-ICDs are their ability to pace (antitachycardia pacing [ATP], bradycardia support and cardiac resynchronisation therapy [CRT]) and the robust evidence base supporting their use. Other benefits include a longer battery life. Significant complications associated with transvenous leads include pneumothorax and tamponade during insertion and infection and lead failure in the long term. Comparatively, S-ICDs, by virtue of having no intravascular leads, prevent these complications. S-ICDs have been associated with a higher incidence of inappropriate shocks. Patients with an indication for bradycardia pacing, CRT or ATP (documented ventricular tachycardia) are seen as unsuitable for a S-ICD. If venous access is unsuitable or undesirable, S-ICDs should be considered given the patient is appropriately screened. There is a need for further randomised controlled trials to directly compare the two devices. TV-ICDs are an effective therapy for preventing SCD limited by significant lead-related complications. S-ICDs are an important development hindered largely by an inability to pace. Young patients stand to gain the most from a S-ICD as the cumulative risk of lead-related complications is high. A clinical framework to aid decision-making is presented.

Development of the Implantable Cardioverter-Defibrillator: JACC Historical Breakthroughs in Perspective

Implantable cardioverter-defibrillators (ICDs) represent transformational technology, arguably the most significant advance in cardiovascular medicine in 50 years. The vision and determination of pioneers Mirowski and Mower was fundamental to this monumental achievement, working with limited resources and confronted by skepticism/criticism from medical establishment. The inventors were followed >35 years in which a multitude of innovative clinical scientists and engineers introduced technological advances leading to the sophisticated devices in practice today. A pivotal patient experiment with automated termination of ventricular fibrillation (1980) led to U.S. Food and Drug Administration approval. Transvenous lead systems converted ICDs from thoracotomy-based secondary prevention to primary prevention of sudden death devices in countless patients worldwide. ICD acceptance was solidified by prospective randomized controlled trials showing reduced mortality superior to antiarrhythmic drugs. ICDs eventually expanded from coronary disease to inherited arrhythmia conditions (eg, hypertrophic cardiomyopathy). The ICD breakthrough story demonstrates how significant progress is possible in medicine against all odds, given fearless imagination to pursue novel ideas that conflict with accepted wisdom.

Design and rationale of the MODULAR ATP global clinical trial: A novel intercommunicative leadless pacing system and the subcutaneous implantable cardioverter-defibrillator

Background

The subcutaneous implantable cardioverter-defibrillator (S-ICD) has demonstrated safety and efficacy for the treatment of malignant ventricular arrhythmias. However, a limitation of the S-ICD lies in the inability to either pace-terminate ventricular tachycardia or provide prolonged bradycardia pacing support.

Objective

The rationale and design of a prospective, single-arm, multinational trial of an intercommunicative leadless pacing system integrated with the S-ICD will be presented.

Methods

A technical description of the modular cardiac rhythm management (mCRM) system (EMPOWER leadless pacemaker and EMBLEM S-ICD) and the implantation procedure is provided. MODULAR ATP (Effectiveness of the EMPOWER™ Modular Pacing System and EMBLEM™ Subcutaneous ICD to Communicate Antitachycardia Pacing) is a multicenter, international trial enrolling up to 300 patients at risk of sudden cardiac death at up to 60 centers trial design. The safety endpoint of freedom from major complications related to the mCRM system or implantation procedure at 6 months and 2 years are significantly higher than 86% and 81%, respectively, and all-cause survival is significantly >85% at 2 years.

Results

Efficacy endpoints are that at 6 months mCRM communication success is significantly higher than 88% and the percentage of subjects with low and stable thresholds is significantly higher than 80%. Substudies to evaluate rate-responsive features and performance of the pacing module are also described.

Conclusion

The MODULAR ATP global clinical trial will prospectively test the safety and efficacy of the first intercommunicating leadless pacing system with the S-ICD. This trial will allow for robust validation of device-device communication, pacing performance, rate responsiveness, and system safety.

Arrhythmogenicity of anti-tachycardia pacing in patients with implantable cardioverter defibrillator

BACKGROUND

Anti-tachycardia pacing therapy (ATP) has shown comparable efficacy to shock therapy in ventricular tachycardia (VT) termination with better quality of life. However, some ATPs may lead to VT acceleration or degeneration to ventricular fibrillation (VF), which will result in more ICD shocks. The aim of this study was to investigate the predictors of VT acceleration by ATP therapy in a real-life patient cohort.

RESULTS

We retrospectively reviewed 448 monomorphic VT episodes that required ATP therapy in 60 patients with structural heart diseases implanted with ICD or CRTD. The clinical data of the patients and the episodes' details were evaluated. We found that patients with a higher ejection fraction (EF) were more likely to be cardioverted by ATP therapy (P: 0.024). VT acceleration was more frequent in patients with lower EF (mean 31.24 ± 4.08) compared with the non-accelerated patients with higher EF (mean 37.00 ± 9.4, P: 0.016). The percentage of accelerated episodes was 8.5%. VT episodes with a mean cycle length (CL) < 310 ms are more likely to accelerate (sensitivity 76.3%, specificity 67.7%, PPV value 45%, NPV 86%, and AUC 0.790). There was a statistically significant difference in the accelerated VT episodes as compared to non-accelerated episodes regarding the number of ATP bursts (mean 3.66 ± 2.22 vs. 1.76 ± 1.35, P: < 0.001), ramp (23.7% vs. 4.2%, P: < 0.001), scanning (55.3% vs. 31.3%, P: 0.003) and burst adaptive cycle length (mean 83.55 ± 2.92 vs. 84.64 ± 2.61, P: 0.016). In a multivariate analysis, the VT CL, number of ATP bursts and ramp pacing predicted VT acceleration by ATP therapy.

CONCLUSIONS

Ventricular tachycardia in patients with low LV EF and fast VTs with a CL less than 310 ms were more likely to accelerate with ATP therapy. The number of ATP bursts and the use of ramp had a significant effect on VT acceleration. To avoid VT acceleration by ATP therapy, ramp pacing better be avoided, especially in fast VTs, and lesser number of bursts should be delivered.

Ventricular Tachycardia and ICD Therapy Burden With Catheter Ablation Versus Escalated Antiarrhythmic Drug Therapy

BACKGROUND

Catheter ablation improves ventricular tachycardia (VT) event-free (time to event) survival in patients with antiarrhythmic drug (AAD)-refractory VT and previous myocardial infarction (MI). The effects of ablation on recurrent VT and implantable cardioverter-defibrillator (ICD) therapy (burden) have yet to be investigated.

OBJECTIVES

This study sought to compare the VT and ICD therapy burden following treatment with either ablation or escalated AAD therapy among patients with VT and previous MI in the VANISH (Ventricular tachycardia AblatioN versus escalated antiarrhythmic drug therapy in ISchemic Heart disease) trial.

METHODS

The VANISH trial randomized patients with previous MI and VT despite initial AAD therapy to either escalated AAD treatment or catheter ablation. VT burden was defined as the total number of VT events treated with ≥1 appropriate ICD therapy. Appropriate ICD therapy burden was defined as the total number of appropriate shocks or antitachycardia pacing therapies (ATPs) delivered. The Anderson-Gill recurrent event model was used to compare burden between the treatment arms.

RESULTS

Of the 259 enrolled patients (median age, 69.8 years; 7.0% women), 132 patients were randomized to ablation and 129 patients were randomized to escalated AAD therapy. Over 23.4 months of follow-up, ablation-treated patients had a 40% lower shock-treated VT event burden and a 39% lower appropriate shock burden compared with patients who received escalated AAD therapy (P <0.05 for all). A reduction in VT burden, ATP-treated VT event burden, and appropriate ATP burden among ablation patients was only demonstrated in the stratum of patients with amiodarone-refractory VT (P <0.05 for all).

CONCLUSIONS

Among patients with AAD-refractory VT and a previous MI, catheter ablation reduced shock-treated VT event burden and appropriate shock burden compared with escalated AAD therapy. There was also lower VT burden, ATP-treated VT event burden, and appropriate ATP burden among ablation-treated patients; however, the effect was limited to patients with amiodarone-refractory VT.

Right ventricular function is a predictor for sustained ventricular tachycardia requiring anti-tachycardic pacing in arrhythmogenic ventricular cardiomyopathy: insight into transvenous vs. subcutaneous implantable cardioverter defibrillator insertion

AIMS

Arrhythmogenic right ventricular cardiomyopathy (ARVC) patients develop ventricular arrhythmias (VAs) responsive to anti-tachycardia pacing (ATP). However, VA episodes have not been characterized in accordance with the device therapy, and with the emergence of the subcutaneous implantable cardioverter defibrillator (S-ICD), the appropriate device prescription in ARVC remains unclear. Study aim was to characterize VA events in ARVC patients during follow-up in accordance with device therapy and elicit if certain parameters are predictive of specific VA events.

METHODS AND RESULTS

This was a retrospective single-centre study utilizing prospectively collated registry data of ARVC patients with ICDs. Forty-six patients were included [54.0 ± 12.1 years old and 20 (43.5%) secondary prevention devices]. During a follow-up of 12.1 ± 6.9 years, 31 (67.4%) patients had VA events [n = 2, 6.5% ventricular fibrillation (VF), n = 14], 45.2% VT falling in VF zone resulting in ICD shock(s), n = 10, 32.3% VT resulting in ATP, and n = 5, 16.1% patients had both VT resulting in ATP and ICD shock(s). Lead failure rates were high (11/46, 23.9%). ATP was successful in 34.5% of patients. Severely impaired right ventricular (RV) function was an independent predictor of VT resulting in ATP (hazard ratio 16.80, 95% confidence interval 3.74-75.2; P < 0.001) with a high predictive accuracy (area under the curve 0.88, 95%CI 0.76-1.00; P < 0.001).

CONCLUSION

VA event rates are high in ARVC patients with a majority having VT falling in the VF zone resulting in ICD shock(s). S-ICDs could be of benefit in most patients with ARVC with the absence of severely impaired RV function which has the potential to avoid consequences of the high burden of lead failure.

Reduced inferior wall longitudinal strain is associated with malignant arrhythmias in non-ischemic heart failure

BACKGROUND

Reduced systolic myocardial function in the inferior region of the left ventricle has been suggested to be associated with malignant arrhythmias. We tested this hypothesis in patients with non-ischemic heart failure.

METHODS

Patients with non-ischemic heart failure (left ventricular ejection fraction [LVEF] < 35%) were evaluated by 2D-speckle-tracking echocardiography. The regional longitudinal strain was calculated for each of the six left ventricular walls. The reduced regional function was defined as strain below the median. The outcome was a composite of sudden cardiac death, admission with sustained ventricular arrhythmia, resuscitated cardiac arrest, and appropriate therapy from a primary prophylactic implantable cardioverter defibrillator. Time-to-first-event analysis was performed using a Cox model.

RESULTS

From two centers, 401 patients were included (median age: 63 years, 72% male) with a median LVEF of 25% (interquartile range [IQR] 20;30), and a median inferior wall strain of -9.0% (-12.5; -5.4). During a median follow-up of 4.0 years, 52 outcomes occurred. After multivariate adjustment for clinical and electrocardiographic parameters, inferior wall strain was independently associated with the outcome (HR 2.50 [1.35; 4.62], p = .003). No independent association was found between the composite outcome and reduced strain in any of the other left ventricular walls, Global Longitudinal Strain (HR 1.66 [0.93; 2.98], p = .09), or LVEF (HR 1.33 [0.75; 2.33], p = .33).

CONCLUSIONS

Below median strain in the left ventricular inferior region was independently associated with a 2.5-fold increase in the risk of malignant arrhythmias and sudden cardiac death in patients with non-ischemic heart failure.

EHRA expert consensus document on the management of arrhythmias in frailty syndrome, endorsed by the Heart Rhythm Society (HRS), Asia Pacific Heart Rhythm Society (APHRS), Latin America Heart Rhythm Society (LAHRS), and Cardiac Arrhythmia Society of Southern Africa (CASSA)

There is an increasing proportion of the general population surviving to old age with significant chronic disease, multi-morbidity, and disability. The prevalence of pre-frail state and frailty syndrome increases exponentially with advancing age and is associated with greater morbidity, disability, hospitalization, institutionalization, mortality, and health care resource use. Frailty represents a global problem, making early identification, evaluation, and treatment to prevent the cascade of events leading from functional decline to disability and death, one of the challenges of geriatric and general medicine. Cardiac arrhythmias are common in advancing age, chronic illness, and frailty and include a broad spectrum of rhythm and conduction abnormalities. However, no systematic studies or recommendations on the management of arrhythmias are available specifically for the elderly and frail population, and the uptake of many effective antiarrhythmic therapies in these patients remains the slowest. This European Heart Rhythm Association (EHRA) consensus document focuses on the biology of frailty, common comorbidities, and methods of assessing frailty, in respect to a specific issue of arrhythmias and conduction disease, provide evidence base advice on the management of arrhythmias in patients with frailty syndrome, and identifies knowledge gaps and directions for future research.

Electrical Stimulation for Low-Energy Termination of Cardiac Arrhythmias: a Review

Cardiac arrhythmias are a leading cause of morbidity and mortality in the developed world, estimated to be responsible for hundreds of thousands of deaths annually. Our understanding of the electrophysiological mechanisms of such arrhythmias has grown since they were formally characterized in the late nineteenth century, and this has led to the development of numerous devices and therapies that have markedly improved outcomes for patients affected by such conditions. Despite these advancements, the application of a single large shock remains the clinical standard for treating deadly tachyarrhythmias. Such defibrillating shocks are undoubtedly effective in terminating such arrhythmias; however, they are applied without forewarning, contributing to the patient's stress and anxiety; they can be intensely painful; and they can have adverse psychological and physiological effects on patients. In recent years, there has been interest in developing defibrillation protocols that can terminate arrhythmias without crossing the human pain threshold for energy delivery, generally estimated to be between 0.1 and 1 J. In this article, we review existing literature on the development of such low-energy defibrillation methods and their underlying mechanisms, in an attempt to broadly describe the current landscape of these technologies.

Ventricular tachyarrhythmia treatment and prevention by subthreshold stimulation with stretchable epicardial multichannel electrode array

The implantable cardioverter-defibrillator (ICD) is an effective method to prevent sudden cardiac death in high-risk patients. However, the transvenous lead is incompatible with large-area electrophysiological mapping and cannot accommodate selective multichannel precision stimulations. Moreover, it involves high-energy shocks, resulting in pain, myocardial damage, and recurrences of ventricular tachyarrhythmia (VTA). We present a method for VTA treatment based on subthreshold electrical stimulations using a stretchable epicardial multichannel electrode array, which does not disturb the normal contraction or electrical propagation of the ventricle. In rabbit models with myocardial infarction, the infarction was detected by mapping intracardiac electrograms with the stretchable epicardial multichannel electrode array. Then, VTAs could be terminated by sequential electrical stimuli from the epicardial multichannel electrode array beginning with low-energy subthreshold stimulations. Last, we used these subthreshold stimulations to prevent the occurrence of additional VTAs. The proposed protocol using the stretchable epicardial multichannel electrode array provides opportunities toward the development of innovative methods for painless ICD therapy.

Subcutaneous and Transvenous Defibrillators in Arrhythmogenic Right Ventricular Cardiomyopathy: A Comparison of Clinical and Quality-of-Life Outcomes

BACKGROUND

There is limited evidence guiding the selection between subcutaneous and transvenous implantable cardioverter-defibrillators (ICDs) in patients with arrhythmogenic right ventricular cardiomyopathy (ARVC) at risk for sudden death.

OBJECTIVES

This study aimed to compare clinical and quality-of-life outcomes between transvenous and subcutaneous ICDs among patients with ARVC.

METHODS

Patients with a subcutaneous ICD (n = 57) were matched to patients with a transvenous ICD (n = 88) based on sex, proband status, primary prevention or secondary prevention, monomorphic ventricular tachycardia before implantation, and year of implantation. Appropriate therapy for ventricular arrhythmia, inappropriate shocks, and complications were compared. Quality-of-life surveys were conducted annually.

RESULTS

The matched cohort (median age of 35 years, 43% men, 78% proband, and 37% secondary prevention device) were prospectively followed for 5.1 ± 2.5 years. No significant difference was observed in the rate of appropriate ICD shocks. The subcutaneous group had more inappropriate shocks (23% vs 10%) and fewer procedure-related complications (4% vs 14%) than the transvenous group (P < 0.05). The association between ICD type and the composite of inappropriate shock and complication was not statistically significant (subcutaneous vs transvenous adjusted HR: 1.43; 95% CI: 0.72-2.84). A subcutaneous ICD was associated with more body image concerns and range of motion than a transvenous ICD (P < 0.05).

CONCLUSIONS

In patients with ARVC receiving an ICD, the risk of inappropriate shocks from a subcutaneous ICD should be balanced against the significant vascular complication risk from a transvenous ICD. Patients with a subcutaneous ICD had more concerns for body image and range of motion.

Antitachycardia pacing success in implantable cardioverter-defibrillators by patient, device, and programming characteristics

BACKGROUND

Antitachycardia pacing (ATP) is an established implantable cardioverter-defibrillator (ICD) therapy that terminates ventricular tachycardias (VTs) without painful ICD shocks. However, factors influencing ATP success are not well understood.

OBJECTIVE

The purpose of this study was to examine ATP success rates by patient, device, and programming characteristics.

METHODS

This retrospective analysis of the PainFree SmartShock Technology study included spontaneous ATP-treated monomorphic VT episodes. ATP success rates were calculated for various factors. Also, the relationship of ATP programming on shock burden and syncope were investigated.

RESULTS

Of the 2770 enrolled patients (2200 [79%] male; mean age 65 years), 1699 (61%) received an ICD and 1071 (39%) a cardiac resynchronization therapy - defibrillator. ATP had >80% rate of success for terminating VTs overall, with similar rates observed between ICD and cardiac resynchronization therapy - defibrillator devices (82.2% vs 80.3%, respectively; P = .81) as well as between primary and secondary prevention patients with ICDs (77.2% vs 83.9% respectively; P = .25). Arrhythmias with a median cycle length of ≥320 ms had a significantly higher ATP success rate (88.0%; 95% confidence interval 84.8%-90.6%). The cumulative percentage of ATP success increased from 71% at 1 ATP sequence delivered to 87% at ≥8 sequences delivered. Programming more ATP sequences was associated with lower shock burden (P = .0005). There was no evidence that more sequences were associated with higher rates of syncope (P = .16).

CONCLUSION

Delivering more ATP sequences resulted in a higher overall success of terminating VTs, while programming more ATP was associated with decreased shock burden and no evidence of increased syncope or acceleration. This suggests that more ATP sequences should be programmed when possible, but confirmation in prospective studies will be necessary.

Conduction of excitation waves and reentry drift on cardiac tissue with simulated photocontrol-varied excitability

The development of new approaches to suppressing cardiac arrhythmias requires a deep understanding of spiral wave dynamics. The study of spiral waves is possible in model systems, for example, in a monolayer of cardiomyocytes. A promising way to control cardiac excitability in vitro is the noninvasive photocontrol of cell excitability mediated by light-sensitive azobenzene derivatives, such as azobenzene trimethylammonium bromide (AzoTAB). The trans-isomer of AzoTAB suppresses spontaneous activity and excitation propagation speed, whereas the cis isomer has no detectable effect on the electrical properties of cardiomyocyte monolayers; cis isomerization occurs under the action of near ultraviolet (UV) light, and reverse isomerization occurs when exposed to blue light. Thus, AzoTAB makes it possible to create patterns of excitability in conductive tissue. Here, we investigate the effect of a simulated excitability gradient in cardiac cell culture on the behavior and termination of reentry waves. Experimental data indicate a displacement of the reentry wave, predominantly in the direction of lower excitability. However, both shifts in the direction of higher excitability and shift absence were also observed. To explain this effect, we reproduced these experiments in a computer model. Computer simulations showed that the explanation of the mechanism of observed drift to a lower excitability area requires not only a change in excitability coefficients (ion currents) but also a change in the diffusion coefficient; this may be the effect of the substance on intercellular connections. In addition, it was found that the drift direction depended on the observation time due to the meandering of the spiral wave. Thus, we experimentally proved the possibility of noninvasive photocontrol and termination of spiral waves with a mechanistic explanation in computer models.

Management of hemodynamically stable wide QRS complex tachycardia in patients with implantable cardioverter defibrillators

Management of hemodynamically stable, incessant wide QRS complex tachycardia (WCT) in patients who already have an implantable cardioverter defibrillator (ICD) is challenging. First-line treatment is performed by medical staff who have no knowledge on programmed ICD therapy settings and there is always some concern for unexpected ICD shock. In these patients, a structured approach is necessary from presentation to therapy. The present review provides a systematic approach in four distinct phases to guide any physician involved in the management of these patients: PHASE I: assessment of hemodynamic status and use of the magnet to temporarily suspend ICD therapies, especially shocks; identification of possible arrhythmia triggers; risk stratification in case of electrical storm (ES).

PHASE II

The preparation phase includes reversal of potential arrhythmia "triggers", mild patient sedation, and patient monitoring for therapy delivery. Based on resource availability and competences, the most adequate therapeutic approach is chosen. This choice depends on whether a device specialist is readily available or not. In the case of ES in a "high-risk" patient an accelerated patient management protocol is advocated, which considers urgent ventricular tachycardia transcatheter ablation with or without mechanical cardiocirculatory support.

PHASE III

Therapeutic phase is based on the use of intravenous anti-arrhythmic drugs mostly indicated in this clinical context are presented. Device interrogation is very important in this phase when sustained monomorphic VT diagnosis is confirmed, then ICD ATP algorithms, based on underlying VT cycle length, are proposed. In high-risk patients with intractable ES, intensive patient management considers MCS and transcatheter ablation.

PHASE IV

The patient is hospitalized for further diagnostics and management aimed at preventing arrhythmia recurrences.

Race, Sex, and Neighborhood Socioeconomic Disparities in Ablation of Ventricular Tachycardia Within a National Medicare Cohort

Background Ventricular tachycardia (VT) ablation significantly improves our ability to control VT, yet little is known about whether disparities exist in delivery of this technology. Methods and Results Using a national 100% Medicare inpatient data set of beneficiaries admitted with VT from January 1, 2014, through November 30, 2014, multivariable logistic regression techniques were used to examine the sociodemographic and clinical characteristics associated with receiving ablation. Census block group-level neighborhood socioeconomic disadvantage was measured for each patient by the Area Deprivation Index, a composite measure of socioeconomic disadvantage consisting of education, income, housing, and employment factors. Among 131 645 patients admitted with VT, 2190 (1.66%) received ablation. After adjustment for comorbidities, hospital characteristics, and sociodemographics, female sex (odds ratio [OR], 0.75 [95% CI, 0.67-0.84]), identifying as Black race (OR, 0.75 [95% CI, 0.62-0.90] compared with identifying as White race), and living in a highly socioeconomically disadvantaged neighborhood (national Area Deprivation Index percentile of >85%) (OR, 0.81 [95% CI, 0.69-0.95] versus Area Deprivation Index ≤85%) were associated with significantly lower odds of receiving ablation. Conclusions Female patients, patients identifying as Black race, and patients living in the most disadvantaged neighborhoods are 19% to 25% less likely to receive ablation during hospitalization with VT. The cause of and solutions for these disparities require further investigation.

Evolution of extravascular implantable cardioverter-defibrillator therapy for ventricular arrhythmias

Implantable cardioverter-defibrillators have become an established therapy for the prevention of sudden cardiac death due to life-threatening ventricular arrhythmias in the last decades. In all those years, the use of transvenous leads has proven to be the most vulnerable part of the system. The development of the completely subcutaneous implantable cardioverter-defibrillator opened a new era of device therapy outside of the vascular system. The next step, enabling extravascular devices with the option of antitachycardia pacing, is just around the corner. This may become an important option for all patients without a bradycardia pacing indication that are in need for antitachycardia pacing because of monomorphic ventricular tachycardia.

The physics of heart rhythm disorders

The global burden caused by cardiovascular disease is substantial, with heart disease representing the most common cause of death around the world. There remains a need to develop better mechanistic models of cardiac function in order to combat this health concern. Heart rhythm disorders, or arrhythmias, are one particular type of disease which has been amenable to quantitative investigation. Here we review the application of quantitative methodologies to explore dynamical questions pertaining to arrhythmias. We begin by describing single-cell models of cardiac myocytes, from which two and three dimensional models can be constructed. Special focus is placed on results relating to pattern formation across these spatially-distributed systems, especially the formation of spiral waves of activation. Next, we discuss mechanisms which can lead to the initiation of arrhythmias, focusing on the dynamical state of spatially discordant alternans, and outline proposed mechanisms perpetuating arrhythmias such as fibrillation. We then review experimental and clinical results related to the spatio-temporal mapping of heart rhythm disorders. Finally, we describe treatment options for heart rhythm disorders and demonstrate how statistical physics tools can provide insights into the dynamics of heart rhythm disorders.

Transvenous or subcutaneous implantable cardioverter defibrillator: a review to aid decision-making

The implantable cardioverter-defibrillator (ICD) is a proven treatment for preventing sudden cardiac death. Transvenous leads are associated with significant mortality and morbidity, and the subcutaneous ICD (S-ICD) addresses this. However, it is not without limitations, in particular the absence of anti-tachycardia pacing. The decision of which device is most suitable for an individual patient is often complex. Here, we review the relative merits and weaknesses of both the transvenous and S-ICD. We summarise the available evidence for each device in particular patient cohorts, namely: ischaemic and non-ischaemic cardiomyopathy, idiopathic ventricular fibrillation, Brugada syndrome, long QT syndrome, arrhythmogenic right ventricular cardiomyopathy, and hypertrophic cardiomyopathy.

Evaluation of the Novel Automated Anti-Tachycardia Pacing Algorithm Successfully Terminating Sustained Monomorphic Ventricular Tachycardia in an Electrophysiology Study

We report the usefulness of novel automated anti-tachycardia pacing (ATP) for ventricular tachycardia (VT) termination evaluated in an electrophysiology study. This intrinsic, automated ATP with an implanted cardiac resynchronization therapy-defibrillator successfully terminated the sustained VT, which had not been suppressed by repetitive burst pacing from the electrode catheter. The reproduction of programed pacing of the automated ATP by a right ventricular electrode catheter was effective in terminating VT, and this termination was absolute and reproducible. Further detailed assessment in an electrophysiology study could highlight the algorithm of the automated ATP and its possible benefit in terminating the reentrant VT.

Optimal entrainment for removal of pinned spiral waves

Cardiac fibrillation is caused by self-sustaining spiral waves that occur in the myocardium, some of which can be pinned to anatomical obstacles, making them more difficult to eliminate. A small electrical stimulation is often sufficient to unpin these spirals but only if it is applied during the vulnerable unpinning window. Even if these unpinning windows can be inferred from data, when multiple pinned spirals exist, their unpinning windows will not generally overlap. Using phase-based reduction techniques, we formulate and solve an optimal control problem to yield a time-varying external voltage gradient that can synchronize a collection of spiral waves that are pinned to a collection of heterogeneous obstacles. Upon synchronization, the unpinning windows overlap so that they can be simultaneously unpinned by applying an external voltage gradient pulse at an appropriate moment. Numerical validation is presented in bidomain model simulations. Results represent a proof-of-concept illustration of the proposed unpinning strategy which explicitly incorporates heterogeneity in the problem formulation and requires no real-time feedback about the system state.

Subcutaneous ICD Implantation and Catheter Ablation

Secondary prevention of sudden cardiac death in the young patient with arrhythmogenic right ventricular cardiomyopathy and hemodynamically tolerated ventricular tachycardia is still a challenging field. We present a combined approach, including subcutaneous implantable cardioverter-defibrillator (ICD) and catheter ablation, as a promising treatment to prevent both ventricular tachycardia recurrences and ICD shocks. (Level of Difficulty: Intermediate.)

Efficacy and Safety of Appropriate Shocks and Antitachycardia Pacing in Transvenous and Subcutaneous Implantable Defibrillators: Analysis of All Appropriate Therapy in the PRAETORIAN Trial

BACKGROUND

The PRAETORIAN trial (A Prospective, Randomized Comparison of Subcutaneous and Transvenous Implantable Cardioverter Defibrillator Therapy) showed noninferiority of subcutaneous implantable cardioverter defibrillator (S-ICD) compared with transvenous implantable cardioverter defibrillator (TV-ICD) with regard to inappropriate shocks and complications. In contrast to TV-ICD, S-ICD cannot provide antitachycardia pacing for monomorphic ventricular tachycardia. This prespecified secondary analysis evaluates appropriate therapy and whether antitachycardia pacing reduces the number of appropriate shocks.

METHODS

The PRAETORIAN trial was an international, investigator-initiated randomized trial that included patients with an indication for implantable cardioverter defibrillator (ICD) therapy. Patients with previous ventricular tachycardia <170 bpm or refractory recurrent monomorphic ventricular tachycardia were excluded. In 39 centers, 849 patients were randomized to receive an S-ICD (n=426) or TV-ICD (n=423) and were followed for a median of 49.1 months. ICD programming was mandated by protocol. Appropriate ICD therapy was defined as therapy for ventricular arrhythmias. Arrhythmias were classified as discrete episodes and storm episodes (≥3 episodes within 24 hours). Analyses were performed in the modified intention-to-treat population.

RESULTS

In the S-ICD group, 86 of 426 patients received appropriate therapy, versus 78 of 423 patients in the TV-ICD group, during a median follow-up of 52 months (48-month Kaplan-Meier estimates 19.4% and 17.5%; P=0.45). In the S-ICD group, 83 patients received at least 1 shock, versus 57 patients in the TV-ICD group (48-month Kaplan-Meier estimates 19.2% and 11.5%; P=0.02). Patients in the S-ICD group had a total of 254 shocks, compared with 228 shocks in the TV-ICD group (P=0.68). First shock efficacy was 93.8% in the S-ICD group and 91.6% in the TV-ICD group (P=0.40). The first antitachycardia pacing attempt successfully terminated 46% of all monomorphic ventricular tachycardias, but accelerated the arrhythmia in 9.4%. Ten patients with S-ICD experienced 13 electrical storms, versus 18 patients with TV-ICD with 19 electrical storms. Patients with appropriate therapy had an almost 2-fold increased relative risk of electrical storms in the TV-ICD group compared with the S-ICD group (P=0.05).

CONCLUSIONS

In this trial, no difference was observed in shock efficacy of S-ICD compared with TV-ICD. Although patients in the S-ICD group were more likely to receive an ICD shock, the total number of appropriate shocks was not different between the 2 groups. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT01296022.

Patterned Illumination Techniques in Optogenetics: An Insight Into Decelerating Murine Hearts

Much has been reported about optogenetic based cardiac arrhythmia treatment and the corresponding characterization of photostimulation parameters, but still, our capacity to interact with the underlying spatiotemporal excitation patterns relies mainly on electrical and/or pharmacological approaches. However, these well-established treatments have always been an object of somehow heated discussions. Though being acutely life-saving, they often come with potential side-effects leading to a decreased functionality of the complex cardiac system. Recent optogenetic studies showed the feasibility of the usage of photostimulation as a defibrillation method with comparatively high success rates. Although, these studies mainly concentrated on the description as well as on the comparison of single photodefibrillation approaches, such as locally focused light application and global illumination, less effort was spent on the description of excitation patterns during actual photostimulation. In this study, the authors implemented a multi-site photodefibrillation technique in combination with Multi-Lead electrocardiograms (ECGs). The technical connection of real-time heart rhythm measurements and the arrhythmia counteracting light control provides a further step toward automated arrhythmia classification, which can lead to adaptive photodefibrillation methods. In order to show the power effectiveness of the new approach, transgenic murine hearts expressing channelrhodopsin-2 ex vivo were investigated using circumferential micro-LED and ECG arrays. Thus, combining the best of two methods by giving the possibility to illuminate either locally or globally with differing pulse parameters. The optical technique presented here addresses a number of challenges of technical cardiac optogenetics and is discussed in the context of arrhythmic development during photostimulation.

Influence of "high" defibrillation thresholds on patient survival and impact of system modification

OBJECTIVE

To test whether a high defibrillation threshold (DFT) marks patients with poor outcomes which are improved when DFT is decreased by system modification (subcutaneous coil implant; SM).

BACKGROUND

The electrical substrate generating fast ventricular arrhythmias may generate poor outcomes among patients treated with implantable cardioverter-defibrillators (ICDs), even when arrhythmias are treated successfully. Since patients with high DFTs have increased mortality, we contrasted survival among patients with high DFT treated with and without SM.

METHODS

We studied consecutive patients undergoing ICD implantation and DFT testing at Cleveland Clinic over a 14-year period. High DFT was defined as successful defibrillation by shock strength >25 J or ≤10 J of maximal device output. Mortality was recorded using the Social Security Death Index. Survival was compared among those high DFT patients receiving SM versus the remainder.

RESULTS

Out of 6353 patients tested, 191 (3%) had high DFT (32.1 ± 3.7 J) versus 13.9 ± 4.9 J in the remainder ("acceptable DFT," p < .001). One hundred twenty-one high DFT patients (63%; 33.3 ± 3.4 J) underwent SM, which significantly decreased DFT (24.8 ± 5.9 J; p < .001). Seventy patients (37%; 30.3 ± 3.3 J) did not undergo SM. During follow-up, 38% (2363/6162; 7.8 yrs) patients with acceptable DFT died versus 48% high DFT patients (91/191; 5.6 yrs.; p < .001). Concomitantly, 48% patients with SM (58/121) died, as compared to 47% patients (33/70) without SM (p = .91); median follow-up 4.9 yrs).

CONCLUSION

Patients with high DFT have a higher mortality than those with acceptable DFT. The additional subcutaneous coil implant decreases DFT to an acceptable range but does not appear to improve survival. The electrical substrate underlying high DFT appears to determine survival.

Trends in implantable cardioverter-defibrillator programming practices and its impact on therapies: Insights from a North American Remote Monitoring Registry 2007-2018

BACKGROUND

Recent evidence has revealed the utility of prolonged arrhythmia detection duration and increased rate cutoff to reduce implantable cardioverter-defibrillator (ICD) therapies. Data on real-world trends in ICD programming and its impact on outcomes are limited.

OBJECTIVE

The purpose of this study was to evaluate trends in ICD programming and its impact on ICD therapy using a large remote monitoring database.

METHODS

A retrospective analysis of patients with ICD implanted from 2007 to 2018 was conducted using the de-identified Medtronic CareLink database. Data on ICD programming (number of intervals to detection [NID] and therapy rate cutoff) and delivered ICD therapies were collected.

RESULTS

Among 210,810 patients, the proportion programmed to a rate cutoff of ≥188 beats/min increased from 41% to 49% and an NID of ≥30/40 increased from 17% to 67% before May 2013 vs after February 2016. Programming to a rate cutoff of ≥188 beats/min, a ventricular fibrillation (VF) NID of ≥30/40, or a combined rate cutoff of ≥188 beats/min and VF NID of ≥30/40 were associated with reductions in ICD therapy. The largest reductions in ICD therapy occurred when the combination of rate cutoff ≥ 188 beats/min and VF NID ≥ 30/40 was programmed (antitachycardia pacing: hazard ratio [HR] 0.35; 95% confidence interval [CI] 0.34-0.36; P < .001; shocks: HR 0.67; 95% CI 0.65-0.69; P < .001; and antitachycardia pacing/shocks: HR 0.43; 95% CI 0.42-0.44; P < .001).

CONCLUSION

Despite evidence supporting the use of prolonged detection duration and high rate cutoff, implementation of shock reduction programming strategies in real-world clinical practice has been modest. The use of evidence-based ICD programming is associated with reduced ICD shocks over long-term follow-up.

Clinical management of electrical storm: a current overview

The number of patients affected by electrical storm has been continuously increasing in emergency departments. Patients are often affected by multiple comorbidities requiring multidisciplinary interventions to achieve a clinical stability. Careful reprogramming of cardiac devices, correction of electrolyte imbalance, knowledge of underlying heart disease and antiarrhythmic drugs in the acute phase play a crucial role. The aim of this review is to provide a comprehensive overview of pharmacological treatment, latest transcatheter ablation techniques and advanced management of patients with electrical storm.

Assessment of primary prevention patients receiving an ICD - Systematic evaluation of ATP: APPRAISE ATP

Background

The value of antitachycardia pacing (ATP) in the overall cohort of primary prevention patients who receive implantable cardioverter-defibrillators (ICDs) remains uncertain. ATP success reported in prior trials potentially included a large number of patients receiving unnecessary ATP for arrhythmias that may have self-terminated owing to the prematurity of the intervention. Although some patients derive benefit from initial ATP in terminating rapid ventricular arrhythmias and thereby preventing shocks, there are limited data allowing us to identify those patients a priori.

Objective

The purpose of APPRAISE ATP is to understand the role of ATP in primary prevention patients currently indicated for ICD therapy in a large prospective randomized controlled trial with modern programming parameters.

Methods

The study is a global, prospective, randomized, multicenter clinical trial conducted at up to 150 sites globally, enrolling approximately 2600 subjects The primary endpoint of the trial is time to first all-cause shock in a 2-arm study with an equivalent study design in which the incidence of all-cause shocks will be compared between primary prevention subjects programmed with shocks only vs subjects programmed to standard therapy (ATP and shock).

Results

An Electrogram and Device Interrogation Core Laboratory will review interrogation data to determine primary endpoints that occur in APPRAISE ATP. Their decisions are based on independent physician review of the data from device interrogation.

Conclusion

The ultimate purpose of the study is to aid clinicians in the selection of ICD technologies based on hard endpoint evidence across the spectrum of indications for primary prevention implantation.

RR interval variability in the evaluation of ventricular tachycardia and effects of implantable cardioverter defibrillator therapy

BACKGROUND

An implantable cardioverter defibrillator (ICD) is the most reliable therapeutic device for preventing sudden cardiac death in patients with sustained ventricular tachycardia (VT). Regarding its effectiveness, targeted VT is defined based on the tachyarrhythmia cycle length. However, variations in RR interval variability of VTs may occur. Few studies have reported on VT characteristics and effects of ICD therapy according to the RR interval variability. We aimed to identify the clinical characteristics of VTs and ICD therapy effects according to the RR interval variability.

METHODS

We analyzed 821 VT episodes in 69 patients with ICDs or cardiac resynchronization therapy defibrillators. VTs were classified as irregular when the difference between two successive beats was >20 ms in at least one of 10 RR intervals; otherwise, they were classified as regular. We evaluated successful termination using anti-tachycardia pacing (ATP)/shock therapy, spontaneous termination, and acceleration between regular and irregular VTs. The RR interval variability reproducibility rates were evaluated.

RESULTS

Regular VT was significantly more successfully terminated than irregular VT by ATP. No significant difference was found in shock therapy or VT acceleration between the regular and irregular VTs. Spontaneous termination occurred significantly more often in irregular than in regular VT cases. The reproducibility rates of RR interval variability in each episode and in all episodes were 89% and 73%, respectively.

CONCLUSIONS

ATP therapy showed greater effectiveness for regular than for irregular VT. Spontaneous termination was more common in irregular than in regular VT. RR interval variability of VTs seems to be reproducible.

Anti-tachycardia pacing for non-fast and fast ventricular tachycardias in individual Japanese patients: From Nippon-storm study

BACKGROUND

Anti-tachycardia pacing (ATP) delivered from an implantable device is a useful tool to terminate ventricular tachycardia (VT). But its real-world efficacy for those patients having multiple VTs with varying VT rates has not been fully studied.

METHODS

Using the Nippon-storm study database, efficacy of patient-by-patient basis ATP programing for Japanese patients having both non-fast (120-187 bpm) and fast VT (≥188 bpm) was assessed. According to the useful criteria of ≥50% success termination by ATP, patients were divided into three subgroups; success ≥50% for both non-fast and fast VT (both useful), ≥50% only for non-fast VT (non-fast VT useful), or ≥50% for neither non-fast nor fast VT (neither useful).

RESULTS

During a median follow-up of 28 months, ATP terminated 184 of the 203 non-fast VT episodes (91%) and 86 of the 113 fast VT episodes (76%) in all 41 patients. In the patient-by-patient analysis, efficacy of ATP was not different between non-fast and fast VT in most of the patients (36/41 = 88%); 32 patients were in the both useful and four other patients in the neither useful. Neither ischemic nor non-ischemic structural heart disease was associated with the ATP efficacy, whereas LVEF more than 37.0% and non-prescribed amiodarone were characteristics of the patients classified into the both useful.

CONCLUSIONS

ATP well terminated both non-fast and fast VT occurring in individual Japanese patients with various structural heart diseases in the real-world device treatment and this finding further supports ATP programing for all device tachycardia detection zones in most patients with multiple VTs.

Expert consensus on acute management of ventricular arrhythmias - VT network Austria

The Arrhythmia Working Group of the Austrian Society of Cardiology (ÖKG) has set the goal of systematically structuring and organizing the acute care of patients with ventricular arrhythmias (VA), i.e. ventricular tachycardia (VT) or ventricular fibrillation (VF) in Austria. Within a consensus paper, national recommendations on the basic diagnostic work-up of VA (12-lead ECG, medical history, family history, laboratory analyses, echocardiography, search for reversible causes, ICD interrogation), as well as further medical treatment and therapeutic measures (indication of coronary angiography, ablation therapy) are established. Since acute ablation of VT is indicated in the current ESC guidelines as a class IB indication for scar-associated incessant VT or electrical storm (ES; ≥ 3 ICD therapies in 24 h) as well as for ischemic cardiomyopathy (iCMP) with recurrent ICD shocks, organizational measures must be taken to ensure that these guidelines can be implemented. Therefore, a VT network will be established covering all areas in Austria, consisting of primary and secondary VT centers. Organizational aspects of an acute VT network are defined and should subsequently be implemented by the participating hospitals. All electrophysiologic centers in Austria that deal with VT ablation are to be integrated into the network in the medium-term. Centers that co-operate in the network are divided into primary and secondary VT centers according to predefined criteria.

Prediction of paroxysmal atrial fibrillation using new heart rate variability features

Paroxysmal atrial fibrillation (PAF) is a cardiac arrhythmia that can eventually lead to heart failure or stroke if left untreated. Early detection of PAF is therefore crucial to prevent any further complications and avoid fatalities. An implantable defibrillator device could be used to both detect and treat the condition though such devices have limited computational capability. With this constraint in mind, this paper presents a novel set of features to accurately predict the presence of PAF. The method is evaluated using ECG signals from the widely used atrial fibrillation prediction database (AFPDB) from PhysioNet. We analysed 106 signals from 53 pairs of ECG recordings. Each pair of signals contains one 5-min ECG segment that ends just before the onset of a PAF event and another 5-min ECG segment at least 45 min distant from the PAF event, to represent a non-PAF event. Seven novel features are extracted through the Poincaré representation of R-R interval signals, and are prioritised through feature ranking schemes. The features are used with four standard classification techniques for PAF prediction and compared to the existing state of the art from the literature. Using only the seven proposed features, classification performance outperforms those of the classical state-of-the-art feature set, registering sensitivity and specificity measurements of over 96%. The results further improve when the features are combined with several of the classical features, with an accuracy increasing to 98% using a linear kernel SVM. The results show that the proposed features provide a useful representation of the PAF condition and achieve good prediction with off-the-shelf classification techniques that would be suitable for ICU deployment.