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

Analyses of inappropriate shocks in a Spanish ICD primary prevention population: Predictors and prognoses

BACKGROUND

ICDs have been demonstrated to be highly effective in the primary prevention of sudden death, but inappropriate shocks (IS) occur frequently and represent one of the most important adverse effects of ICDs. The aim of this study was to analyze IS and identify the clinical predictors and prognostic implications of ISs in a real-world primary prevention ICD population.

METHODS

This multicenter retrospective study was performed in 13 centers with experience in the field of ICD implantation (at least 30 per year) and ICD follow-up in Spain. All consecutive patients who underwent ICD implantation for primary prevention between January 2008 and May 2014 were included.

RESULTS

One-thousand-sixteen patients were included, and 4 (0.39%) were lost to follow-up. Two-hundred-seventeen (21.4%) patients suffered from shock; 69 (6.8%) of these patients experienced IS, and 154 (15.4%) experienced appropriate shocks (AS). Age (<65 years, hazard ratio (HR) 2.588 [95% CI 1.282-5.225]; p=0.008), history of atrial fibrillation (HR 2.252 [95% CI 1.230-4.115]; p=0.009), non-ischemic myocardiopathy (HR 2.258 [95% CI 1.090-4.479]; p=0.028), and cardiac resynchronization therapy (HR 0.385 [95% CI 0.200-0.740]; p=0.004) were identified as IS predictors in a multivariate analysis. IS was not associated with rehospitalization due to heart failure, myocardial infarction, cardiovascular mortality or all-cause mortality.

CONCLUSIONS

This analysis of our national registry identified the independent IS predictors of age, atrial fibrillation history and cardiac resynchronization therapy and suggests that ISs are not linked to poorer clinical endpoints.

Shock Reduction With Multiple Bursts of Antitachycardia Pacing Therapies to Treat Fast Ventricular Tachyarrhythmias in Patients With Implantable Cardioverter Defibrillators: A Multicenter Study

INTRODUCTION

An empirical sequence of burst antitachycardia pacing (ATP) is effective in terminating fast ventricular tachycardias (FVT) in patients with implantable cardioverter-defibrillators (ICDs). We aimed to determine whether multiple ATP bursts for termination of FVT results in shock reduction compared to a single ATP burst.

METHODS AND RESULTS

We analyzed data from the Umbrella trial, a multicenter prospective observational study of ICD patients followed by the CareLink Monitoring System. We compared the safety and effectiveness of a single ATP burst (Group 1) with a strategy of successive ATP sequences (Group 2) for termination of FVT episodes (cycle lengths 250-320 milliseconds) before shock therapy. Over a mean follow-up of 35 months, a total of 650 FVT episodes were detected in 154 patients (mean cycle length: 299 ± 18 milliseconds). Effectiveness of the first burst ATP in Group 1 was 73% and shocks were required in 27% of episodes. Effectiveness of the first burst ATP in Group 2 was 77%, and this increased to 91% with the third or successive ATP bursts. Shocks were required in 9% of episodes in group 2, representing a 67% reduction in the need of high-energy shocks. Median duration of FVT episodes and mortality in both groups were similar. Multivariate analysis indicated that programming multiple ATP bursts (OR 3.4, 95%CI 1.7-6.8, P = 0.001) was an independent predictor of ATP effectiveness.

CONCLUSION

This study provides first evidence that a strategy of multiple burst ATP sequences for termination of FVT episodes leads to a clinically meaningful reduction in the need for shocks.

Reduction of inappropriate ICD therapies in patients with primary prevention of sudden cardiac death: DECREASE study

BACKGROUND

A significant number of patients with an implantable cardioverter/defibrillator (ICD) for primary prevention receive inappropriate shocks. Previous studies have reported a reduction of inappropriate therapies with simple modifications of ICD detection settings, however, inclusion criteria and settings varied markedly between studies. Our aim was to investigate the effect of raising the ICD detection zone in the entire primary prevention ICD population.

METHODS AND RESULTS

543 patients receiving an ICD for primary prevention were randomized to either conventional or progressive ICD programming. The detection rate was programmed at 171 bpm for ventricular tachycardia (VT) and 214 bpm for ventricular fibrillation (VF) in the Conventional group and 187 bpm for VT and 240 bpm for VF in the Progressive group. 43 % of patients received single-chamber and 57 % dual-chamber detection devices (DDD-ICD 19 %; CRT-D 38 %). The primary endpoint consisted of inappropriate therapies and untreated VT/VF. The primary endpoint was reached in 35 patients (13 %) in the Conventional group and 17 patients (6 %) in the Progressive group (p = 0.004). Progressive ICD programming led to significantly fewer amount of patients with ICD therapies (26 vs. 14 %; p < 0.001) and shocks (11 vs. 5 %; p = 0.023) compared to conventional ICD programming. Sub-analyses showed the greatest reduction of inappropriate therapies and shocks in dual-chamber detection devices with progressive compared to single-chamber detection devices with conventional ICD programming (p < 0.001).

CONCLUSIONS

Progressive ICD programming reduces the number of inappropriate therapies and shocks in a broad primary prevention ICD population particularly in combination with dual-chamber detection algorithms.

CLINICAL TRIAL REGISTRATION

http://clinicaltrials.gov ; ClinicalTrials.gov identifier NCT01217528.

Management of ventricular arrhythmias in structural heart disease

Ventricular arrhythmias (VA) are a source of significant morbidity and mortality in patients with structural heart disease (SHD). The advent of the implantable cardiac defibrillator (ICD) has had a positive effect on mortality, but the associated morbidity remains a significant problem. Modern treatment of VA has advanced far beyond medical therapy and includes strategies as simple as intelligent ICD programming and as complex as catheter ablation (CA). In these pages, the spectrum of management strategies will be discussed; from anti-arrhythmic drugs and ICD implantation and programming to CA and autonomic modulation. The focus of this review will be on strategies for secondary prevention of VA in patients with SHD, supported by clinical evidence for their utilization.

Programming implantable cardioverter-defibrillator therapy zones to high ranges to prevent delivery of inappropriate device therapies in patients with primary prevention: results from the RISSY-ICD (Reduction of Inappropriate ShockS bY InCreaseD zones) trial

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

The clinical course of patients with implantable cardioverter-defibrillators: Extended experience on clinical outcome, device replacements, and device-related complications

BACKGROUND

Large randomized trials demonstrated the beneficial effect of implantable cardioverter-defibrillator (ICD) and cardiac resynchronization therapy-defibrillator (CRT-D) treatments in selected patients. Data on long-term follow-up of patients outside the setting of clinical trials are scarce.

OBJECTIVE

The aim of this study was to evaluate the long-term outcome of ICD and CRT-D recipients.

METHODS

All patients who underwent ICD (n = 1729 [57%]) or CRT-D (n = 1326 [43%]) implantation at the Leiden University Medical Center since 1996 were evaluated. Follow-up visits were performed every 3-6 months, and events were registered. Cumulative incidence curves of device therapy and device-related complications were adjusted for the competing risk of all-cause mortality.

RESULTS

After a median follow-up of 5.1 years (25th-75th percentile 3.1-7.8 years), 842 patients (28%) died. The cumulative incidence of all-cause mortality was 49% (95% confidence interval [CI] 45%-54%) in ICD recipients after 12 years of follow-up and 55% (95% CI 52%-58%) in CRT-D recipients after 8 years of follow-up. A total of 1081 patients (35%) received appropriate defibrillator therapy. The cumulative incidence of appropriate therapy in ICD patients was 58% (95% CI 54%-62%) after 12 years of follow-up and 39% (95% CI 35%-43%) in CRT-D patients after 8 years of follow-up. Twelve-year cumulative incidences of adverse events were 20% (95% CI 18%-22%) for inappropriate shock, 6% (95% CI 5%-8%) for device-related infection, and 17% (95% CI 14%-21%) for lead failure.

CONCLUSION

After long-term follow-up of ICD (12 years) and CRT-D (8 years) recipients, 49% of ICD recipients and 55% of CRT-D recipients had died. Appropriate ICD therapy was received by the majority (58%) of ICD recipients and by almost 40% of CRT-D recipients.

Antitachycardia pacing for reduction of implantable cardioverter-defibrillator shocks

Antitachycardia pacing (ATP) strategies represent safe, effective, and painless therapy for ventricular tachyarrhythmias, with a large body of clinical evidence supporting their routine use in both primary and secondary implantable cardioverter-defibrillator recipients. This article details the evidence supporting the use of standardized and validated ATP strategies for primary prevention patients and the conceptual framework to design effective ATP strategy for secondary prevention patients.

Clinical course and prognostic relevance of antitachycardia pacing-terminated ventricular tachyarrhythmias in implantable cardioverter-defibrillator patients

AIMS

In patients with an implantable cardioverter-defibrillator (ICD), ICD shocks due to ventricular tachycardia (VT) or ventricular fibrillation (VF) have been associated with an increased mortality. It is not known whether patients with antitachycardia pacing (ATP)-terminated VT/VF episodes have a similar worse outcome. The aim of this study was to evaluate the clinical course and prognostic impact of ATP-terminated episodes on mortality in ICD patients.

METHODS AND RESULTS

A total of 1398 consecutive patients of the prospective single-centre ICD-registry Ludwigshafen who underwent an ICD implantation between 1992 and 2008 for primary or secondary prevention of sudden cardiac death were analysed. Patients treated with ATP were compared with patients with appropriate ICD shocks or patients without any appropriate ATP or ICD shock. During the median follow-up time of 6 years, 749 (54%) patients experienced 17 827 episodes of VT or VF which were terminated by ATP in 74% and by shock in 26% of patients. In approximately half (n = 321/749) of those patients with VT/VF, the first episode was terminated by ATP. In a multivariate analysis adjusted for different baseline confounding parameters, the occurrence of first ATP therapy was associated with a higher mortality rate [hazard ratio (HR) 2.60, 95% confidence interval (CI) 2.02-3.35]. When excluding all patients with appropriate ICD shocks first ATP therapy remained associated with a worse prognosis (HR 1.92, 95% CI 1.38-2.67).

CONCLUSIONS

In ICD patients, about three-fourths of ventricular arrhythmias are terminated by ATP. The occurrence of ATP-terminated episode is associated with an increased mortality rate.

The implantable cardioverter-defibrillator: An update

The implantable cardioverter-defibrillator (ICD) provides life-saving therapy to prevent sudden cardiac death. ICDs have been implanted in millions of patients worldwide since the first human implant in 1980. Clinical trials have helped establish guidelines for ICD implantation in primary and secondary prevention of sudden cardiac death. Recent trials have also tested and compared various programing strategies to avoid unnecessary shocks and improve survival among ICD recipients. ICDs may also assist with monitoring for heart failure management. In this review, we discuss the clinical science to date that has helped define the role of ICDs in current practice.

Psychological effects of implantable cardioverter defibrillator shocks. A review of study methods

Background: The implantable cardioverter defibrillator (ICD) saves lives but clinical experience suggests that it may have detrimental effects on mental health. The ICD shock has been largely blamed as the main offender but empirical evidence is not consistent, perhaps because of methodological differences across studies.

Objective: To appraise methodologies of studies that assessed the psychological effects of ICD shock and explore associations between methods and results.

Data Sources: A comprehensive search of English articles that were published between 1980 and 30 June 2013 was applied to the following electronic databases: PubMed, EMBASE, NHS HTA database, PsycINFO, Sciencedirect and CINAHL.

Review Methods: Only studies testing the effects of ICD shock on psychological and quality of life outcomes were included. Data were extracted according to a PICOS pre-defined sheet including methods and study quality indicators.

Results: Fifty-four observational studies and six randomized controlled trials met the inclusion criteria. Multiple differences in methods that were used to test the psychological effects of ICD shock were found across them. No significant association with results was observed.

Conclusions: Methodological heterogeneity of study methods is too wide and limits any quantitative attempt to account for the mixed findings. Well-built and standardized research is urgently needed.

Examination of the differential impacts of antitachycardia pacing vs. shock on patient activity in the EMPIRIC study

AIMS

Implantable cardioverter defibrillators (ICDs) have demonstrated mortality advantages over antiarrhythmic drug therapy, but ICD shock has known detrimental effects on quality of life and psychologic functioning. However, it remains unknown how patient activity level is affected by shock, or by antitachycardia pacing (ATP), which was developed to reduce the treatment burden of shocks. Examine the differential impact of ICD shock and ATP on patient activity level as a novel way to capture the relative behavioural repercussions of these ICD therapies.

METHODS AND RESULTS

Accelerometer-derived activity data were analysed for a subset of patients (males = 83%; mean age = 62 years) enrolled in the EMPIRIC trial who received shock (n = 71) or ATP (n = 103). Differences in activity between a week pre-therapy and a week post-therapy were examined to assess the behavioural repercussions of shock vs. ATP when one, few (2-4), or many (5+) therapies were delivered. For patients receiving shock, a significant reduction in activity was observed for few (-26%) and many shocks (-34%) in the first week post-therapy (P < 0.05). In weeks 2-4, activity levels recovered towards baseline levels. In contrast, no level of ATP-only therapy significantly reduced patients' activity levels at any time following therapy.

CONCLUSION

This study is the first to evaluate objective, behavioural effects of shock, and whether these effects are comparable with ATP therapy alone. In tandem with existing literature, current results highlight that ICD shocks and ATP have divergent effects on behavioural outcomes, with ATP's effect profile in these domains appearing somewhat favourable.

ICD programming to reduce shocks and improve outcomes

Despite the clinical benefit of implantable cardioverter defibrillator (ICD), there is a high frequency of inappropriate ICD therapy associated with impaired quality of life, unwanted health care resource utilization, and adverse clinical outcome. Alternative strategies of ICD programming are needed to reduce the risk of inappropriate and "unnecessary" ICD therapies and to improve patient outcome. In this review, we provide an overview of the rate of inappropriate and appropriate ICD therapies in clinical trials and large registries as well as a review of current trials evaluating novel ICD programming to reduce inappropriate ICD therapy to avoid unnecessary ICD therapy. Based on recent studies including a large randomized trial, we recommend a simple programming approach involving high-rate device therapy beginning at 200 bpm with a 2.5 sec delay for it reduces inappropriate therapy, unnecessary therapy, and all-cause mortality in patients receiving ICD or CRT-D devices for primary prevention indications.

Programming implantable cardioverter/defibrillators and outcomes

Implantable cardioverter-defibrillators are complex technical devices with a multitude of programming options for the physician. In recent years, numerous randomized trials have been performed to define the optimal programming strategies and have provided valuable insights, especially in primary prevention patients. This article provides an actual overview on the existing evidence on the most important programming features for accurate detection and therapy of ventricular arrhythmias.

Optimal programming management of ventricular tachycardia storm in ICD patients

Ventricular tachycardia storm (VTS) is defined as a life-threatening syndrome of three or more separate episodes of ventricular tachycardia (VT) leading to implantable cardioverter defibrillator (ICD) therapy within 24 hours. Patients with VTS have poor outcomes and require immediate medical attention. ICD shocks have been shown to be associated with increased mortality in several studies. Optimal programming in minimization of ICD shocks may decrease mortality. Large controlled trials showed that long detection time and high heart rate detection threshold reduced ICD shock burden without an increase in syncope or death. As a fundamental therapy of ICD, antitachycardia pacing (ATP) can terminate most slow VT with a low risk of acceleration. For fast VT, burst pacing is more effective and less likely to result in acceleration than ramp pacing. One algorithm of optimal programming management during a VTS is presented in the review.

The subcutaneous ICD-current evidence and challenges

The subcutaneous implantable cardioverter-defibrillator (S-ICD) represents an exciting development in ICD technology. It has relative advantages over traditional transvenous systems, particularly for young patients in whom the lifetime risk of device-related complications may be deemed to be unacceptably high. While data relating to device longevity and long term safety profile is yet to be accrued, several recent studies have demonstrated good clinical efficacy comparable to transvenous ICDs. Indeed, new techniques have also been developed to simplify the S-ICD implantation procedure and attempts have been made to address challenges pertaining to T-wave oversensing to reduce the delivery of inappropriate shocks. The impact of inappropriate shocks and lack of anti-tachycardia pacing (ATP) function are not only contentious matters, but also have important implications for patients in whom the S-ICD would be suitable. It is envisaged that subsequent models of this device will be less cumbersome, with the possibility that an entirely leadless pacemaker-defibrillator will one day be possible. Although the S-ICD may not completely replace transvenous devices in its current form, evidence suggests that it is a viable alternative particularly in preventing sudden cardiac death in non-pacing dependent patients.

Device therapies: new indications and future directions

Implantable cardioverter-defibrillator (ICDs), cardiac resynchronization (CRT) and combination (CRT-D) therapy have become an integral part of the management of patients with heart failure with reduced ejection fraction (HFrEF). ICDs treat ventricular arrhythmia and CRTs improve left ventricular systolic function by resynchronizing ventricular contraction. Device therapies (ICD, CRT-D), have been shown to reduce all-cause mortality, including sudden cardiac death. Hospitalizations are reduced with CRT and CRT-D therapy. Major device related complications include device infection, inappropriate shocks, lead malfunction and complications related to extraction of devices. Improvements in device design and implantation have included progressive miniaturization and increasing battery life of the device, optimization of response to CRT, and minimizing inappropriate device therapy. Additionally, better definition of the population with the greatest benefit is an area of active research.

Nonlinear and Stochastic Dynamics in the Heart

In a normal human life span, the heart beats about 2 to 3 billion times. Under diseased conditions, a heart may lose its normal rhythm and degenerate suddenly into much faster and irregular rhythms, called arrhythmias, which may lead to sudden death. The transition from a normal rhythm to an arrhythmia is a transition from regular electrical wave conduction to irregular or turbulent wave conduction in the heart, and thus this medical problem is also a problem of physics and mathematics. In the last century, clinical, experimental, and theoretical studies have shown that dynamical theories play fundamental roles in understanding the mechanisms of the genesis of the normal heart rhythm as well as lethal arrhythmias. In this article, we summarize in detail the nonlinear and stochastic dynamics occurring in the heart and their links to normal cardiac functions and arrhythmias, providing a holistic view through integrating dynamics from the molecular (microscopic) scale, to the organelle (mesoscopic) scale, to the cellular, tissue, and organ (macroscopic) scales. We discuss what existing problems and challenges are waiting to be solved and how multi-scale mathematical modeling and nonlinear dynamics may be helpful for solving these problems.

Ventricular tachyarrhythmia recurrence in primary versus secondary implantable cardioverter-defibrillator patients and role of electrophysiology study

PURPOSE

In recent years, there has been a shift away from performing electrophysiologic study (EPS) to guide implantable cardioverter-defibrillator (ICD) implantation with a reliance on left ventricular ejection fraction (LVEF) alone.

METHODS

ICD patients were prospectively recruited from the multicentre COMFORT (Concept of Optimal Management of ventricular Fibrillation Or Very fast ventricular Tachycardia) trial. Primary prevention ICD patients (n = 260, groups 1 and 2) were compared to secondary prevention ICD patients (n = 210, group 3). Primary prevention ICDs were implanted in patients with ischemic cardiomyopathy based on LVEF ≤ 40 % and inducible ventricular tachycardia (VT) at EPS (n = 123, group 1) or impaired LVEF alone (LVEF ≤ 30 % or LVEF ≤ 35 % with NYHA class II or III; n = 137, group 2). EPS was performed in 61 % of secondary prevention ICD patients (n = 129). Patients were followed up for >12 months with a primary endpoint of spontaneous VT/ventricular fibrillation (VF).

RESULTS

A significantly higher rate of spontaneous VT/VF occurred in secondary versus primary prevention ICD patients (P < 0.001) and in EPS-guided versus LVEF-guided primary prevention ICD patients (P = 0.029). At 2 years, the proportion of patients with ≥1 VT/VF episode was 24.6 ± 4.2 %, 19.9 ± 4.6 % and 37.1 ± 3.9 % for groups 1, 2 and 3, respectively. In the secondary prevention, patients who underwent EPS, VT/VF occurred in 44.4 ± 5.9 % and 14.1 ± 6.6 % with a positive versus negative result, respectively (P = 0.02).

CONCLUSIONS

Secondary prevention ICD patients have more spontaneous VT/VF than primary prevention ICD patients. Secondary and primary prevention ICD patients with inducible VT at EPS have more VT/VF than patients without inducible VT or impaired LVEF alone.

Efficacy of anti-tachycardia pacing for terminating fast ventricular tachycardia in Japanese implantable cardioverter defibrillator patients. Primary results of the SATISFACTION study

BACKGROUND

Anti-tachycardia pacing (ATP) delivered by implantable cardioverter defibrillators (ICD) safely avoids painful shocks with minimum risk of tachycardia acceleration. The etiology of ventricular tachycardia (VT) in those studies, however, was predominantly coronary artery disease (CAD). Patient etiology differs by geography and could affect ATP efficacy rate. The primary objective of this study was to examine how often the first ATP therapy terminates fast VT (FVT) in Japanese ICD patients with regional etiologies. METHODS AND RESULTS: Seven hundred and fifteen patients received ICD or cardiac resynchronization therapy defibrillator with the function of ATP during capacitor charging. The primary endpoint was the first ATP success rate for terminating FVT with cycle length 240-320 ms. During a mean follow-up of 11.3 months, 888 spontaneous VT episodes were detected, including 276 FVT (31.1%) in 42 patients. The first-ATP success rate for FVT in the overall group (41% CAD, 59% non-CAD including 23% idiopathic VT) was 62.1% (61.7% adjusted). Success rate was not different between non-CAD and CAD patients (61.4% adjusted and 57.5% adjusted, respectively, P=0.75). Eight FVT episodes (2.9%) accelerated after the first ATP attempt, all of which were terminated by subsequent device therapy (additional ATP or shock).

CONCLUSIONS

ATP efficacy for FVT was similar between ICD patients with and without CAD etiology.

Effectiveness of antitachycardia pacing therapy after primary prophylaxis implantation of implantable defibrillators in coronary artery disease patients

PURPOSE

Effectiveness of implantable defibrillators (ICD) has been proven with large randomized trials. Unfortunately, ICD discharge is painful and potentially threatening for the patient despite its life saving effects. We analyzed influence of the clinical parameters present before implantation on the effectiveness of antitachycardia pacing therapy (ATP) in terminating ventricular tachycardia (VT) slower than 200 bpm in the coronary artery disease patients with prophylactic implanted ICD in a single centre retrospective trial.

PATIENTS/METHODS

We analyzed 121 consecutive coronary disease patients with ICD implanted in primary prophylaxis between 2001 and 2007, with the mean age of 62 ± 10 years. The mean follow-up was 876 ± 538 days.

RESULTS

32 of them had VT. In 27 persons (84.4%) at least one ATP attempt terminate VT. ATP was always successful in 21 patients. We analyzed age, sex, LVEF, NYHA class, widening of QRS complex, atrial fibrillation, type of myocardial infarction or diabetes. There were no significant differences in clinical features between patients with successful and unsuccessful ATP therapy.

CONCLUSIONS

High effectiveness of ATP was shown in this group. There were no clinical factors indicating success of this type of therapy. That could justify programming ATP as the first line therapy in the VT zone in primary prophylaxis coronary artery disease patients to reduce application of shock therapy. It should be possible to apply a single mode of programming when discharging patients after the implantation procedure regardless of the patient's clinical condition. This could help to control and programme the devices, thus reducing the risk of errors.

Mortality reduction in relation to implantable cardioverter defibrillator programming in the Multicenter Automatic Defibrillator Implantation Trial-Reduce Inappropriate Therapy (MADIT-RIT)

BACKGROUND

The benefit of novel implantable cardioverter defibrillator (ICD) programming in reducing inappropriate ICD therapy and mortality was demonstrated in Multicenter Automatic Defibrillator Implantation Trial-Reduce Inappropriate Therapy (MADIT-RIT). However, the cause of mortality reduction remains incompletely evaluated. We aimed to identify factors associated with mortality, with focus on ICD therapy and programming in the MADIT-RIT population.

METHODS AND RESULTS

In MADIT-RIT, 1500 patients with a primary prophylactic indication for ICD or cardiac resynchronization therapy with defibrillator were randomized to 1 of 3 different ICD programming arms: conventional programming (ventricular tachycardia zone ≥170 beats per minute), high-rate programming (ventricular tachycardia zone ≥200 beats per minute), and delayed programming (60-second delay before therapy ≥170 beats per minute). Multivariate Cox models were used to assess the influence of time-dependent appropriate and inappropriate ICD therapy (shock and antitachycardia pacing) and randomized programming arm on all-cause mortality. During an average follow-up of 1.4±0.6 years, 71 of 1500 (5%) patients died: cardiac in 40 patients (56.3%), noncardiac in 23 patients (32.4%), and unknown in 8 patients (11.3%). Appropriate shocks (hazard ratio, 6.32; 95% confidence interval, 3.13-12.75; P<0.001) and inappropriate therapy (hazard ratio, 2.61; 95% confidence interval, 1.28-5.31; P=0.01) were significantly associated with an increased mortality risk. There was no evidence of increased mortality risk in patients who experienced appropriate antitachycardia pacing only (hazard ratio, 1.02; 95% confidence interval, 0.36-2.88; P=0.98). Randomization to conventional programming was identified as an independent predictor of death when compared with patients randomized to high-rate programming (hazard ratio, 2.0; 95% confidence interval, 1.06-3.71; P=0.03).

CONCLUSIONS

In MADIT-RIT, appropriate shocks, inappropriate ICD therapy, and randomization to conventional ICD programming were independently associated with an increased mortality risk. Appropriate antitachycardia pacing was not related to an adverse outcome.

CLINICAL TRIAL REGISTRATION URL

clinicaltrials.gov Unique identifier: NCT00947310.

State of the art of ICD programming: Lessons learned and future directions

The lifesaving benefits of implantable cardioverter defibrillator (ICD) therapy are more and more weighted against possible harm (e.g. unnecessary device therapy, procedural complications, device malfunction etc.) which might have adverse effects on patients' perceived health status and quality of life. Hence, there has been an increasing interest in the optimisation of ICD programming to prevent inappropriate and appropriate but unnecessary device therapy. The purpose of the current report is to give an overview of research into the optimisation of ICD programming and present the design of the on-going ENHANCED-ICD study. The ENHANCED-ICD study is a prospective, safety monitoring study enrolling 60 primary and secondary prophylactic ICD patients at the University Medical Center Utrecht. Patients implanted with any type of ICD with SmartShock technology(TM), and between 18-80 years of age, were eligible to participate. In all patients a prolonged detection of 60/80 intervals was programmed. The primary objective of the study is to investigate whether enhanced programming to further reduce ICD therapies is safe. The secondary objective is to examine the impact of enhanced programming on (i) antitachycardia pacing and shocks (both appropriate and inappropriate) and (ii) quality of life and distress. The first results of the ENHANCED-ICD study are expected in 2015.

Ventricular arrhythmias in super-responders to cardiac resynchronization therapy

INTRODUCTION AND OBJECTIVES

Cardiac resynchronization therapy is associated with improved quality of life and reduced morbidity and mortality in patients with severe ventricular dysfunction and wide QRS. However, its role in the reduction of ventricular arrhythmias is more controversial.

METHODS

We compared the incidence of ventricular arrhythmias in patients who were undergoing cardiac resynchronization therapy with an implantable cardioverter-defibrillator in terms of the degree of echocardiographic response to resynchronization. Patients were classified in 3 subgroups;super-responders, responders, and nonresponders.

RESULTS

We included 196 patients who were followed up for a median 30.1 months [interquartile range, 18.0-55.1 months]. We recorded the presence of ventricular arrhythmias in 37 patients (18.8%); 3 patients (5.9%) in the super-responder group had ventricular arrhythmias vs 14 (22.2%) among the responders and 20 (24.4%) in the group of nonresponders (P = .025). In multivariate analysis, the only independent predictors of the appearance of ventricular arrhythmias were secondary-prevention device implantation (odds ratio = 4.04; 95% confidence interval, 1.52-10.75; P=.005), absence of echocardiographic super-response (odds ratio=3.81; 95% confidence interval, 1.04-13.93; P=043), QRS >160 ms (odds ratio=2.39; 95% confidence interval, 1.00-1.35; P=.049) and treatment with amiodarone (odds ratio=2.47; 95% confidence interval, 1.03-5.91; P=.041).

CONCLUSIONS

The patients classified as super-responders to cardiac resynchronization therapy had a significant reduction in incidence of ventricular arrhythmias by comparison with the other patients. Despite this, arrhythmic episodes do not completely disappear in this subgroup.

[Electrical storm in ICD patients: prevention and treatment]

Medical progress and demographic changes cause a continuous increase in patients with implantable cardioverter-defibrillators (ICD). Up to one third of patients with ICDs for secondary prevention and half of the patients with previous electrical storm (ES) will suffer from (further) ESs. When multiple ICD shocks are reported by patients (ICD storm), appropriate, inappropriate and phantom shocks have to be distinguished. Reported shocks without clinical correlates (phantom) often affect patients suffering from posttraumatic stress syndrome after an ICD storm. Approximately one third of all ICD shocks are inappropriate, most often due to supraventricular tachycardia with fast atrioventricular (AV) nodal conduction or lead failure. Within 10 years after implantation lead failure can be detected in up to 20 % of cases and approximately one third of these failures are only seen after inappropriate ICD shocks. Furthermore, inappropriate shocks are due to oversensing of far field atrial electrograms, T-waves, diaphragmatic potentials and electrical noise.Appropriate ICD shocks can rarely also be stimulated by the proarrhythmogenicity of lead implantation or ICD programming. Modifications of the waiting period to therapy, time to detection, detection window, antitachycardia pacing (ATP) stimulation and supraventricular discrimination algorithms may minimize ICD shocks. Some stimulation algorithms may improve the hemodynamic stability during ES. In addition to ventricular ablation, blockade of the sympathetic autonomic nervous system and antiarrhythmic treatment are the main pillars of ES treatment. The best ES prevention, however, is optimized heart failure treatment, especially when a cardiac resynchronization with defibrillator (CRT-D) system is implanted.

Fragmentation of the paced QRS complex: a marker of antitachycardia pacing effectiveness among ICD patients

INTRODUCTION

The presence of notches in the paced QRS complex (P-QRS) from the right ventricular apex (RVA) reflects delays in the activation of the left ventricle and may therefore be associated with longer times of stimulus conduction. Our objective was to determine prospectively the relationship between the duration of a notch ≥0.1 mV in the P-QRS (DN) and the effectiveness of antitachycardia pacing (ATP).

METHODS AND RESULTS

We followed 286 implantable cardioverter-defibrillator (ICD) patients with left ventricular dysfunction (pacing site: RVA) for 41 ± 27 months. ICD programming was standardized. P-QRS (100 bpm) was obtained at implant (50 mm/s). A total of 955 monomorphic ventricular tachycardias (VTs) with a cycle length of 335 ± 32 milliseconds occurred consecutively in 108 patients. ATP was successful in 84% of VTs. DN correlated with the probability of ineffective ATP (C = 0.67; P < 0.001), the cutoff point with the best sensitivity and specificity being 50 milliseconds. The adjusted mean ATP effectiveness per patient was 76% (95% CI: 72-85). Patients with a DN ≥ 50 milliseconds had a lower ATP efficiency: 67% (56-77) versus 92% (87-97) and a higher proportion of VTs terminated with shocks (SH): 31% (21-42) versus 8% (2-14); P < 0.001 for both. Although the occurrence of VT was similar (41% vs. 40%), the incidence of VT-related SH was higher in patients with a DN ≥ 50 (25% vs. 14%; P = 0.01) in the overall study population (n = 286).

CONCLUSIONS

When ATP is applied to the RVA, a DN ≥ 50 milliseconds is associated with a lower ATP effectiveness and a higher risk of SH due to VT.