Comparison of arrhythmia recurrence in patients presenting with ventricular fibrillation versus ventricular tachycardia in the Antiarrhythmics Versus Implantable Defibrillators (AVID) trial

Prognostic Impact of Different Types of Ventricular Tachyarrhythmias Stratified by Underlying Cardiac Disease

Limited data regarding the outcome of patients with different types of ventricular tachyarrhythmias is available. This study sought to assess the prognostic impact of different types of ventricular tachyarrhythmias stratified by underlying cardiac disease. A large retrospective registry was used including all consecutive patients presenting with ventricular tachycardia (VT) and fibrillation (VF) on admission from 2002 to 2016. Patients with non-sustained VT (ns-VT), sustained VT (s-VT) and VF were compared using uni- and multivariable Cox regression models. Risk stratification was performed after stratification by underlying cardiac disease (i.e., acute myocardial infarction (AMI), ischemic heart disease (IHD), non-ischemic cardiomyopathy (NICM) and patients considered as lower-risk for ventricular tachyarrhythmias). The primary endpoint was defined as all-cause mortality at 2.5 years. Secondary endpoints were cardiac death at 24 h, all-cause mortality at 5 years, cardiac rehospitalization and a composite arrhythmic endpoint at 2.5 years. In 2422 consecutive patients with ventricular tachyarrhythmias, most patients were admitted with VF (44%), followed by ns-VT (30%) and s-VT (26%). Patients with VF suffered most commonly from AMI (42%), whereas heart failure was more common in s-VT patients (32%). In patients with AMI (HR = 1.146; 95% CI 0.751-1.750; p = 0.527) and in the lower-risk group (HR = 1.357; 95% CI 0.702-2.625; p = 0.364), the risk of all-cause mortality did not differ in VF and s-VT patients. In IHD patients, VF was associated with impaired prognosis compared to s-VT (HR = 2.502; 95% CI 1.936-3.235; p = 0.001). In conclusion, VF was associated with worse long-term prognosis compared to s-VT in IHD patients, whereas the risk of all-cause mortality among VF and s-VT patients did not differ in patients with AMI, NICM and in patients considered at lower risk for ventricular tachyarrhythmias.

Cycle length of nonsustanied ventricular tachycardias among ICD patients: implications on subsequent appropriate therapies

Background

ICD patients with episodes of nonsustained ventricular tachycardias (NSVT) are at risk of appropriate therapies. However, the relationship between the cycle length (CL) of such NSVTs and the subsequent incidence of appropriate interventions is unknown.

Methods

416 ICD patients with LVEF < 45% were studied. ICD programming was standardized. NSVT was defined as any VT of 5 or more beats at ≥ 150 bpm occurred in the first 6 months after implantation that terminated spontaneously and was not preceded by any appropriate therapy. The mean follow-up was 41 ± 27 months.

Results

We analyzed 2201 NSVTs (mean CL = 323 ms) that occurred in 250 patients; 111 of such episodes were fast (CL ≤ 300 ms). Secondary prevention (HR = 1.7; p < 0.001), number of NSVT episodes (HR = 1.05; 95% CI 1.04–1.07; p < 0.001) and beta-blocker treatment (HR = 0.7; p = 0.04) were independent predictors of appropriate interventions; however, the mean CL of NSVTs was not (p = 0.6). There was a correlation between the mean CL of NSVTs and the CL of the first monomorphic VT: r = 0.88; p < 0.001. This correlation was especially robust in individuals with > 5 NSVTs (r = 0.97; p < 0.001), with an agreement between both values greater than 95%. Patients with any fast NSVT experienced a higher incidence of VF episodes (26%) compared to those without NVSTs (3%) or with only slow NSVTs (7%); p < 0.001.

Conclusions

Unlike the burden, the CL of NSVTs is not a predictor of subsequent appropriate interventions. However, there is a close relationship between the CL of NSVTs and that of arrhythmias that will later lead to appropriate therapies.

Temporal Incidence of Appropriate and Inappropriate Therapy and Mortality in Secondary Prevention ICD Patients by Cardiac Diagnosis

OBJECTIVES

This study sought to estimate the temporal development in rates and incidences of appropriate and inappropriate implantable cardioverter-defibrillator (ICD) therapy and shocks by cardiac diagnosis in a real-world population of patients with secondary prevention ICDs.

BACKGROUND

Data on cardiac diagnoses and temporal development of ICD therapies in patients with secondary prevention ICDs are limited.

METHODS

Patients (N = 4,587) with a secondary prevention ICD were identified from the Danish Pacemaker and ICD Register (January 1, 2007, to December 31, 2016) and linked to nationwide administrative registers. The outcome of appropriate and inappropriate ICD therapy and all-cause mortality were analyzed by annual event rates, cumulative incidence plots, and Cox regression models.

RESULTS

During a mean follow-up of 3.6 ± 2.4 years, 1,362 patients (30%) experienced appropriate ICD therapy (16.8% shocks), and 350 patients (7.6%) experienced inappropriate ICD therapy (4.6% shocks). From 2007 to 2016, there was a significant temporal reduction in both appropriate and inappropriate ICD therapy from 28.2 (95% confidence interval [CI]: 21.6 to 37.0) to 7.9 (95% CI: 6.8 to 9.1) and 10.0 (95% CI: 6.4 to 15.5) to 1.0 (95% CI: 0.7 to 1.5) per 100 person-years (p for trends <0.001). Multivariate Cox regression analyses showed that arrhythmogenic right ventricular cardiomyopathy was associated with the highest probability of appropriate ICD therapy (hazard ratio: 2.45; 95% CI: 1.77 to 3.39; p < 0.0001), whereas patients with hypertrophic cardiomyopathy had the lowest probability (hazard ratio: 0.62; 95% CI: 0.42 to 0.93; p = 0.0196) when compared to patients with ischemic heart disease.

CONCLUSIONS

In this nationwide real-life cohort of patients with secondary prevention ICDs, we observed a significant temporal decline in delivered appropriate and inappropriate shocks and ICD therapies in the last decade. A large proportion of patients still experienced ICD therapy but with significant differences by cardiac diagnosis.

Secondary prevention of sudden cardiac death

The prevention and treatment of sudden cardiac death (SCD) remains a significant public health challenge. For patients with a history of sudden death attributable to ventricular arrhythmia, implantable cardioverter-defibrillator (ICD) therapy is a mainstay of treatment, although these patients remain at high risk for recurrent ventricular arrhythmia and defibrillator therapies. In this review, we summarize landmark clinical trials evaluating the efficacy of ICD therapy in secondary prevention patients, review clinical outcomes including mode of death in survivors of SCD, and highlight the role for systematic diagnostic evaluation. We additionally discuss the invasive electrophysiological management of these patients, including ICD selection and programming as well as the role and timing of antiarrhythmic drug therapy and catheter ablation. Finally, we frame future challenges and needs to advance the care for secondary prevention patients.

Pan-Asia United States PrEvention of Sudden Cardiac Death Catheter Ablation Trial (PAUSE-SCD): rationale and study design

BACKGROUND

The role of catheter ablation as an adjunct and alternative to ICD implantation is not known in patients at risk for recurrent ventricular tachycardia (VT) and sudden cardiac death (SCD) across Asia. Patients with nonischemic etiologies of cardiomyopathy, which are highly prevalent in Asia, have not been previously enrolled in randomized trials of VT ablation.

OBJECTIVE

To evaluate whether preemptive catheter ablation in patients with monomorphic VT and an indication for ICD implantation results in improved clinical outcomes compared to ICD implantation with standard medical therapy alone. To examine the natural history of ablation outcomes in the absence of background ICD therapy in patients that refuse randomization.

METHODS

The PAUSE-SCD study (NCT02848781) is a prospective, multi-center, randomized controlled trial enrolling patients with structural heart disease (EF < 50%) with an indication for ICD implantation. Patients are randomized in a 1:1 fashion to two treatment arms: ICD with ablation and ICD with standard medical therapy alone. A prospective registry cohort was designed to follow the outcomes of patients who refuse ICD and randomization but elect to receive catheter ablation as primary therapy. The primary endpoint is defined as a composite of recurrent VT, cardiovascular rehospitalization, and death. Pre-specified secondary endpoints include each of the individual components of the primary endpoint in addition to comparison between randomized and registry patients.

CONCLUSION

The PAUSE-SCD study is a prospective, multi-center, randomized, and controlled trial examining the impact of preemptive catheter ablation on cardiovascular outcomes in patients with an indication for ICD at risk for recurrent VT and SCD. It represents the first multi-center VT ablation study in Asia, with a design intended to provide insights into the role of both ICD and ablation therapy in a predominantly nonischemic population.

Evaluation of recurrent ventricular tachyarrhythmias in patients who survived out-of-hospital cardiac arrest due to ventricular fibrillation: eligibility for subcutaneous implantable defibrillator therapy

Purpose

The subcutaneous implantable defibrillator (S-ICD) was developed to avoid complications related to transvenous leads. A trade-off with the S-ICD is the inability to deliver antitachycardia pacing (ATP). Data is scarce about the recurrence and characteristics of ventricular tachyarrhythmias (VTa) during a follow-up in survivors of out-of-hospital cardiac arrest due to ventricular fibrillation (OHCA-VF). The aim of the study is to determine the characteristics of VTa triggering ICD therapy in order to assess whether survivors of OHCA-VF are eligible candidates for the S-ICD.

Methods

All OHCA-VF patients who received a transvenous ICD were identified, 378 patients, age 57 ± 14 years, predominantly male (76%) with ischemic heart disease (58%). Arrhythmic endpoints were appropriate ICD therapies for any ventricular arrhythmia.

Results

Over a median follow-up of 4.5 years, 690 VTa in 91 patients (24%) were terminated by ICD therapy; 70% of patients had < 5 VTa with ICD therapy. VTa with cycle length ≤ 300 ms were mainly (82%) treated by shock, while 83% of VTa with cycle length > 300 ms were treated by ATP. The presence of a remote myocardial infarction (OR 2.07; 95% CI 1.08–3.97) and LVEF ≤ 0.35 (OR 2.09; 95% CI 1.09–4.00) were significantly associated with the occurrence of VTa with cycle length > 300 ms.

Conclusion

S-ICD implantation may be reasonable in survivors of OHCA-VF who present without a remote myocardial infarction and LVEF > 35%.

Ventricular Tachycardia Ablation versus Escalation of Antiarrhythmic Drugs

BACKGROUND

Recurrent ventricular tachycardia among survivors of myocardial infarction with an implantable cardioverter-defibrillator (ICD) is frequent despite antiarrhythmic drug therapy. The most effective approach to management of this problem is uncertain.

METHODS

We conducted a multicenter, randomized, controlled trial involving patients with ischemic cardiomyopathy and an ICD who had ventricular tachycardia despite the use of antiarrhythmic drugs. Patients were randomly assigned to receive either catheter ablation (ablation group) with continuation of baseline antiarrhythmic medications or escalated antiarrhythmic drug therapy (escalated-therapy group). In the escalated-therapy group, amiodarone was initiated if another agent had been used previously. The dose of amiodarone was increased if it had been less than 300 mg per day or mexiletine was added if the dose was already at least 300 mg per day. The primary outcome was a composite of death, three or more documented episodes of ventricular tachycardia within 24 hours (ventricular tachycardia storm), or appropriate ICD shock.

RESULTS

Of the 259 patients who were enrolled, 132 were assigned to the ablation group and 127 to the escalated-therapy group. During a mean (±SD) of 27.9±17.1 months of follow-up, the primary outcome occurred in 59.1% of patients in the ablation group and 68.5% of those in the escalated-therapy group (hazard ratio in the ablation group, 0.72; 95% confidence interval, 0.53 to 0.98; P=0.04). There was no significant between-group difference in mortality. There were two cardiac perforations and three cases of major bleeding in the ablation group and two deaths from pulmonary toxic effects and one from hepatic dysfunction in the escalated-therapy group.

CONCLUSIONS

In patients with ischemic cardiomyopathy and an ICD who had ventricular tachycardia despite antiarrhythmic drug therapy, there was a significantly lower rate of the composite primary outcome of death, ventricular tachycardia storm, or appropriate ICD shock among patients undergoing catheter ablation than among those receiving an escalation in antiarrhythmic drug therapy. (Funded by the Canadian Institutes of Health Research and others; VANISH ClinicalTrials.gov number, NCT00905853.).

Infarct tissue characterization in implantable cardioverter-defibrillator recipients for primary versus secondary prevention following myocardial infarction: a study with contrast-enhancement cardiovascular magnetic resonance imaging

Knowledge about potential differences in infarct tissue characteristics between patients with prior life-threatening ventricular arrhythmia versus patients receiving prophylactic implantable cardioverter-defibrillator (ICD) might help to improve the current risk stratification in myocardial infarction (MI) patients who are considered for ICD implantation. In a consecutive series of (ICD) recipients for primary and secondary prevention following MI, we used contrast-enhanced (CE) cardiovascular magnetic resonance (CMR) imaging to evaluate differences in infarct tissue characteristics. Cine-CMR measurements included left ventricular end-diastolic and end-systolic volumes (EDV, ESV), left ventricular ejection fraction (LVEF), wall motion score index (WMSI), and mass. CE-CMR images were analyzed for core, peri, and total infarct size, infarct localization (according to coronary artery territory), and transmural extent. In this study, 95 ICD recipients were included. In the primary prevention group (n = 66), LVEF was lower (23 ± 9 % vs. 31 ± 14 %; P < 0.01), ESV and WMSI were higher (223 ± 75 ml vs. 184 ± 97 ml, P = 0.04, and 1.89 ± 0.52 vs. 1.47 ± 0.68; P < 0.01), and anterior infarct localization was more frequent (P = 0.02) than in the secondary prevention group (n = 29). There were no differences in infarct tissue characteristics between patients treated for primary versus secondary prevention (P > 0.6 for all). During 21 ± 9 months of follow-up, 3 (5 %) patients in the primary prevention group and 9 (31 %) in the secondary prevention group experienced appropriate ICD therapy for treatment of ventricular arrhythmia (P < 0.01). There was no difference in infarct tissue characteristics between recipients of ICD for primary versus secondary prevention, while the secondary prevention group showed a higher frequency of applied ICD therapy for ventricular arrhythmia.

Electrical storms in patients with an implantable cardioverter defibrillator

PURPOSE

In some patients with an implantable cardioverter defibrillator (ICD), multiple episodes of electrical storm (ES) can occur. We assessed the prevalence, features, and predictors of ES in patients with ICD.

MATERIALS AND METHODS

Eighty-five patients with an ICD were analyzed. ES was defined as the occurrence of two or more ventricular tachyarrhythmias within 24 hours.

RESULTS

Twenty-six patients experienced at least one ES episode, and 16 patients experienced two or more ES episodes. The first ES occurred 209 ± 277 days after ICD implantation. In most ES cases, the index arrhythmia was ventricular tachycardia (65%). There were no obvious etiologic factors at the onset of most ES episodes (57%). More patients with a structurally normal heart (p = 0.043) or ventricular fibrillation (VF) as the index arrhythmia (p = 0.017) were in the ES-free group. Kaplan-Meier estimates and a log-rank test showed that patients with nonischemic dilated cardiomyopathy (DCMP) (log-rank test, p = 0.016) or with left ventricular ejection fraction < 35% (p = 0.032) were more likely to experience ES, and that patients with VF (p = 0.047) were less affected by ES. Cox proportional hazard regression analysis showed that nonischemic DCMP correlated with a greater probability of ES (hazard ratio, 3.71; 95% confidence interval, 1.16-11.85; p = 0.027).

CONCLUSION

ES is a common and recurrent event in patients with an ICD. Nonischemic DCMP is an independent predictor of ES. Patients with VF or with a structurally normal heart are less likely to experience ES.

Chronic Suppression of Ventricular Tachyarrhythmias in Patients with ICDs

In this review, we examine the data evaluating the role of adjuvant therapy with antiarrthymic drugs (AADs) in chronic suppression of ventricular tachyarrhythmias in the patient with an ICD. It must be noted that all uses of AADs for this indication represent "off-label" prescription. No AAD is approved by the Food and Drug Administration (FDA) specifically as a therapy to reduce ICD shocks.

A comparison of empiric to physician-tailored programming of implantable cardioverter-defibrillators: results from the prospective randomized multicenter EMPIRIC trial

OBJECTIVES

The purpose of this randomized study was to determine whether a strategically chosen standardized set of programmable settings is at least as effective as physician-tailored choices, as measured by the shock-related morbidity of implantable cardioverter-defibrillator (ICD) therapy.

BACKGROUND

Programming of ventricular tachyarrhythmia (ventricular tachycardia [VT] or ventricular fibrillation [VF]) detection and therapy for ICDs is complex, requires many choices by highly trained physicians, and directly influences the frequency of shocks and patient morbidity.

METHODS

A total of 900 ICD patients were randomly assigned to standardized (EMPIRIC, n = 445) or physician-tailored (TAILORED, n = 455) VT/VF programming and followed for 1 year.

RESULTS

The primary end point was met: the adjusted percentages of both VT/VF (22.3% vs. 28.7%) and supraventricular tachycardia or other non-VT/VF event episodes (11.9% vs. 26.1%) that resulted in a shock were non-inferior and lower in the EMPIRIC arm compared to the TAILORED arm. The time to first all-cause shock was non-inferior in the EMPIRIC arm (hazard ratio = 0.95, 90% confidence interval 0.74 to 1.23, non-inferiority p = 0.0016). The EMPIRIC trial had a significant reduction of patients with 5 or more shocks for all-cause (3.8% vs. 7.0%, p = 0.039) and true VT/VF (0.9% vs. 3.3%, p = 0.018). There were no significant differences in total mortality, syncope, emergency room visits, or unscheduled outpatient visits. Unscheduled hospitalizations occurred significantly less often (p = 0.001) in the EMPIRIC arm.

CONCLUSIONS

Standardized empiric ICD programming for VT/VF settings is at least as effective as patient-specific, physician-tailored programming, as measured by many clinical outcomes. Simplified and pre-specified ICD programming is possible without an increase in shock-related morbidity.

Prediction of arrhythmic events with positron emission tomography: PAREPET study design and methods

BACKGROUND

In medically-treated patients with ischemic cardiomyopathy, myocardial viability is associated with a worse prognosis than scar. The risk is especially great with hibernating myocardium (chronic regional dysfunction with reduced resting flow), and the excess mortality appears to be due to sudden cardiac death (SCD). Hibernating myocardium also results in sympathetic nerve dysfunction, which has been independently associated with risk of SCD.

OBJECTIVES

PAREPET is a prospective, observational cohort study funded by NHLBI. It is designed to determine whether hibernating myocardium and/or inhomogeneity of sympathetic innervation by positron emission tomography imaging identifies patients with ischemic cardiomyopathy who are at high risk for SCD and cardiovascular mortality.

METHODS

Patients with documented ischemic cardiomyopathy, an ejection fraction of <or=35%, and with no plans for coronary revascularization will be recruited. Major exclusion criteria include: history of resuscitated SCD, sustained VT, ICD discharge, or unexplained syncope; recent myocardial infarction (30 days), percutaneous coronary intervention (3 months), coronary bypass surgery (1 year); or comorbidities that would be expected to reduce life expectancy to <2 years. All patients will undergo transthoracic echocardiography, and dynamic cardiac positron emission tomography to quantify resting perfusion (13N-ammonia), norepinephrine uptake as an index of sympathetic innervation (11C-meta-hydroxyephedrine), and metabolic viability (18F-2-deoxyglucose during glucose-insulin clamp). The development of SCD or cardiovascular mortality will be determined by telephone follow-up every three months. In patients with an implantable cardiac defibrillator, appropriate device discharge will be considered a surrogate for SCD.

CONCLUSION

The PAREPET study will prospectively determine whether the amount of viable dysfunction myocardium and/or cardiac sympathetic dysinnervation is associated with the risk of SCD. It is anticipated that the results of this trial will more specifically identify myocardial substrates of SCD. This will help target therapies intended to reduce arrhythmic death to those patients with the greatest likelihood of benefit.

Frequency and causes of implantable cardioverter-defibrillator therapies: is device therapy proarrhythmic?

Implantable cardioverter-defibrillator (ICD) shocks diminish patients' quality of life, increase health care resource utilization, and may lead to other adverse sequelae. Better understanding of the factors that lead to ICD therapies, and better strategies to avoid unnecessary therapies, are needed to optimize patient outcomes. Data from major randomized clinical trials involving the use of ICDs and cardiac resynchronization therapy-defibrillator devices were reviewed to determine control group mortality rates, control group sudden death rates, and the frequency of appropriate and inappropriate ICD therapies. In all studies that classified deaths, appropriate ICD therapies outnumbered control group sudden cardiac deaths by a factor of 2 to 3. Some of these episodes can be explained by device programming, by the treatment of potentially unsustained tachycardias, and by errors of episode classification. Another underexplored possibility is that device therapy is proarrhythmic. Reasons for frequent therapies and methods to prevent them are discussed, as well as the notion of device proarrhythmia and the potentially detrimental effects of ICD shocks. These issues clearly affect the overall benefit of device therapy and have important implications for patient management and health care delivery.

Analysis of implantable cardioverter defibrillator signals for non conventional cardiac electrical activity characterization

Implantable cardioverter defibrillators (ICDs) can store intracardiac electrograms (EGMs) in sinus rhythm (SR), at the onset of spontaneous ventricular tachyarrhythmias (VT) or during their course. This allows the investigation of unknown features of the heart electrical activity associated with different cardiac rhythms. In this study we propose a non conventional cardiac electrical activity characterization (CEAC) that extracts quantitative information about the power spectrum wideness and variability of the beat-by-beat morphology. We analyze 293 EGMs from 40 patients who underwent implantation of St Jude Medical-Ventritex ICDs that allow the storage of EGMs with two different modes of recording: bipolar (BIP) and unipolar or far-field (FF). The EGMs are studied with this CEAC by (1) exploring differences between the CEAC measured from FF and BIP EGMs during similar cardiac rhythms, and (2) investigating the mode of recording that allows a better separation between SR and VT rhythms. Results show that, with similar cardiac rhythm, the CEACs from FF or BIP recordings are different (for SR rhythm: sensitivity 81.5%, specificity 93.6%; for VT rhythm: sensitivity and specificity 100%); thus FF and BIP EGMs analyze different aspects of cardiac activity. The CEAC applied to FF EGMs distinguishes better EGMs obtained during SR from VT rhythms (VT vs SR with sensitivity 92.7% and specificity 79.7%) than when it is applied to BIP signals (VT vs SR with sensitivity 60% and specificity 73.3%).

Clinical predictors and prognostic significance of electrical storm in patients with implantable cardioverter defibrillators

AIMS

Insufficient data exists regarding predictors of electrical storms (ES) and clinical outcome in patients treated with an implantable cardioverter defibrillator (ICD). The purpose of this study was to delineate a subgroup of patients likely to experience ES and to determine the impact of ES on mortality in ICD recipients.

METHODS AND RESULTS

Baseline characteristics of 307 ICD-treated patients were retrospectively analysed. ES was defined as two or more ventricular tachyarrhythmias within 24 h leading to an immediate electrical therapy (antitachycardia pacing and/or shock), separated by a period of sinus rhythm. Clinical characteristics and survival of 123 patients experiencing a total of 294 episodes of ES (median 2 ES/patient, range 1-9), were compared with those of 184 ES-free patients during a median follow-up of 826 days (inter-quartile 1141 days). Median actuarial duration for the first ES occurrence after ICD implant was 1417 days [95% confidence interval (CI) 1061-2363] with a median follow-up of 816 days (7-4642 days) in ES-free patients. Univariate analysis identified older age, depressed left ventricular ejection fraction (LVEF), ventricular tachycardia (VT) as index arrhythmia, chronic renal failure and absence of lipid-lowering drugs as variables significantly associated with an increased risk of ES. Multivariable Cox analysis confirmed an independent predictive value for chronic renal failure [hazard ratio (HR) 1.54, 95% CI 0.95-2.51, P=0.052], VT (HR 2.20, 95% CI 1.44-3.37, P=0.0003), and LVEF (HR 0.98, 95% CI 0.97-0.99, P=0.027). In contrast, diabetics (HR 0.49, 95% CI 0.27-0.90, P=0.022) were less affected by ES. There was no difference in survival between both groups.

CONCLUSION

ES is frequent but does not increase mortality in ICD's recipients. Patients with severe systolic dysfunction, chronic renal failure and VT as initial arrhythmia are likely to experience ES. Diabetics are less affected by ES.

Prevalence, predictors, and mortality significance of the causative arrhythmia in patients with electrical storm

INTRODUCTION

Electrical storm (ES) is characterized by either refractory ventricular tachycardia (VT) or ventricular fibrillation (VF). However, little is known about the prevalence, predictors, and mortality implications of the causative arrhythmia in ES. We sought to assess the prevalence, predictors, and survival significance of VT and VF as the causative arrhythmia of ES in implantable cardioverter defibrillator (ICD) patients.

METHODS AND RESULTS

Consecutive patients from January 2000 to December 2002 who presented to the ICD clinic with > or = 2 separate ventricular arrhythmic episodes requiring shock within 24 hours were included in the study. ICD interrogation confirmed the number of shocks and provided electrograms for interpretation of the causative arrhythmia. Patients were grouped as VF or VT according to the causative arrhythmia. Their prevalence, predictors, and mortality rates were compared. Of 2,028 patients assessed in the ICD clinic, 208 (10%) presented with ES. VF was the cause of ES in 99 of 208 patients, for an overall prevalence of 48%. Original ICD indication, coronary artery disease, and amiodarone therapy were predictive for the causative arrhythmia. There was no mortality difference between the VT and VF groups; however, both groups had significantly increased mortality compared to a control ICD population without ES.

CONCLUSION

VF is the causative arrhythmia for a sizable proportion of patients with ES. The initial ICD indication, coronary artery disease, and amiodarone therapy are predictors of the causative arrhythmias in ES. There does not appear to be any mortality difference between ES patients with VT and VF, but mortality is increased in patients with ES versus control ICD patients without ES.

Clinical variables predicting inappropriate use of implantable cardioverter-defibrillator in patients with coronary heart disease or nonischemic dilated cardiomyopathy

Inappropriate therapy is a common clinical problem in recipients of implantable cardioverter-defibrillators (ICDs). The present study evaluated whether clinical characteristics could predict inappropriate ICD therapy due to atrial tachyarrhythmias in a series of 260 patients.

Subanalyses of secondary prevention implantable cardioverter-defibrillator trials: antiarrhythmics versus implantable defibrillators (AVID), Canadian Implantable Defibrillator Study (CIDS), and Cardiac Arrest Study Hamburg (CASH)

PURPOSE OF REVIEW

Controlled trials for secondary prevention of sudden death--Antiarrhythmics Versus Implantable Defibrillators (AVID), Canadian Implantable Defibrillator Study (CIDS), and Cardiac Arrest Study Hamburg (CASH)--have been published and subanalyses of them provide useful clinical information on the outcome during the follow-up of this population.

RECENT FINDINGS

Results from a meta-analysis showed a significant risk reduction (RR) of 25 to 27% of total mortality (P < 0.001) and 50 to 52% of arrhythmic death (P < 0.001). Compared with amiodarone, patients treated with an implantable cardioverter-defibrillator (ICD) in AVID had a maximal benefit in survival when the ejection fraction (EF) was between 20 and 34%. In CIDS, the group of higher risk (older than 70 years, EF less than 3.5%, and New York Heart Association class III-IV) presented a 50% RR of mortality. It has been demonstrated that the imbalance in beta-blocker use cannot explain the better survival in the ICD patients. After 3 years the recurrence of arrhythmia was 64% in the ICD group of the AVID trial. Patients enrolled after an episode of ventricular tachycardia were more likely to have appropriate therapy during follow-up. Older age, lower blood pressure, history of atrial fibrillation, diabetes, congestive heart failure, and prior pacemaker were parameters used for high-risk stratification. Conversely, inducibility of ventricular tachyarrhythmias on electrophysiology did not predict death.

SUMMARY

Patients with ICD after ventricular tachyarrhythmias have a 28% RR in total mortality. Individuals with EF between 20 to 34% received the highest benefit with ICD therapy.