Canadian Implantable Defibrillator Study Research Articles

Modes of death in defibrillator patients: Learning from clinical experience

Historically, mortality rates from trials with implantable cardioverter-defibrillator (ICD) treatment arms for primary and secondary prevention have ranged from 6% to 8%. 1 Moss A.J. Hall W.J. Cannom D.S. et al. Multicenter Automatic Defibrillator Implantation Trial InvestigatorsImproved survival with an implanted defibrillator in patients with coronary disease at high risk for ventricular arrhythmia. N Engl J Med. 1996; 335: 1933-1940 Crossref PubMed Scopus (3537) Google Scholar , 2 Moss A.J. Zareba W. Hall W.J. et al. Prophylactic implantation of a defibrillator in patients with myocardial infarction and reduced ejection fraction. N Engl J Med. 2002; 346: 877-883 Crossref PubMed Scopus (5558) Google Scholar , 3 Connolly S.J. Gent M. Roberts R.S. et al. Canadian Implantable Defibrillator Study (CIDS): a randomized trial of the implantable cardioverter defibrillator against amiodarone. Circulation. 2000; 101: 1297-1302 Crossref PubMed Scopus (1357) Google Scholar , 4 The AVID InvestigatorsCauses of death in the Antiarrhythmics Versus Implantable Defibrillators (AVID) Trial. J Am Coll Cardiol. 1999; 34: 1552-1559 Abstract Full Text Full Text PDF PubMed Scopus (89) Google Scholar Mortality rates for cardiac resynchronization therapy with defibrillators (CRT-D) have ranged from 9% to 12%. 5 Bristow M.R. Saxon L.A. Boehmer J. et al. Cardiac-resynchronization therapy with or without an implantable defibrillator in advanced chronic heart failure. N Engl J Med. 2004; 350: 2140-2150 Crossref PubMed Scopus (4734) Google Scholar , 6 Cleland J.G. Daubert J.C. Erdmann E. et al. The effect of cardiac resynchronization on morbidity and mortality in heart failure. N Engl J Med. 2005; 352: 1539-1549 Crossref PubMed Scopus (5130) Google Scholar Annual heart failure mortality rates have been reported at ∼3% 4 The AVID InvestigatorsCauses of death in the Antiarrhythmics Versus Implantable Defibrillators (AVID) Trial. J Am Coll Cardiol. 1999; 34: 1552-1559 Abstract Full Text Full Text PDF PubMed Scopus (89) Google Scholar , with sudden cardiac death rates at 20%–27% in primary prevention trials (MADIT-I, MADIT-II) and 30%–36% in secondary prevention trials (AVID, CIDS). The mode of death in implantable cardioverter-defibrillator and cardiac resynchronization therapy with defibrillator patients: Results from routine clinical practiceHeart RhythmVol. 9Issue 10PreviewAlthough data on the mode of death of implantable cardioverter-defibrillator (ICD) and cardiac resynchronization therapy with defibrillator (CRT-D) patients have been examined in randomized clinical trials, in routine clinical practice data are scarce. To provide reasonable expectations and prognosis for patients and physicians, this study assessed the mode of death in routine clinical practice. Full-Text PDF

Counting Down Before Blasting Off

Since the first generation of implantable cardioverter-defibrillators (ICDs), technologic advances have markedly enhanced their efficacy and safety and improved the accuracy of arrhythmia detection algorithms. Despite these developments, inappropriate therapies for sinus or supraventricular tachyarrhythmias or lead noise remain a major limitation of contemporary ICDs, with a substantial proportion of patients receiving inappropriate shocks. Psychosocial issues appear to reflect the level of distress related to ICD shocks, with fear of shocks associated with increased anxiety, avoidance behaviors, and perceived functional limitations. 1 Sears Jr., S.E. Conti J.B. Understanding implantable cardioverter defibrillator shocks and storms: medical and psychosocial considerations for research and clinical care. Clin Cardiol. 2003; 26: 107-111 Crossref PubMed Scopus (131) Google Scholar , 2 Irvine J. Dorian P. Baker B. et al. Quality of life in the Canadian Implantable Defibrillator Study (CIDS). Am Heart J. 2002; 144: 282-289 PubMed Google Scholar , 3 Kuhl E.A. Dixit N.K. Walker R.L. Conti J.B. Sears S.F. Measurement of patient fears about implantable cardioverter defibrillator shock: an initial evaluation of the Florida Shock Anxiety Scale. Pacing Clin Electrophysiol. 2006; 29: 614-618 Crossref PubMed Scopus (83) Google Scholar Although all ICD recipients are potentially at risk, reported rates of inappropriate shocks are particularly high in the young, growing, and complex population with congenital heart disease. 4 Khairy P. Harris L. Landzberg M.J. et al. Implantable cardioverter-defibrillators in tetralogy of Fallot. Circulation. 2008; 117: 363-370 Crossref PubMed Scopus (352) Google Scholar , 5 Berul C.I. Van Hare G.F. Kertesz N.J. et al. Results of a multicenter retrospective implantable cardioverter-defibrillator registry of pediatric and congenital heart disease patients. J Am Coll Cardiol. 2008; 51: 1685-1691 Abstract Full Text Full Text PDF PubMed Scopus (290) Google Scholar , 6 Khairy P. Harris L. Landzberg M.J. et al. Sudden death and defibrillators in transposition of the great arteries with intra-atrial baffles: a multicenter study. Circ Arrhythm Electrophysiol. 2008; 1: 250-257 Crossref PubMed Scopus (182) Google Scholar , 7 Khairy P. Defibrillators and cardiac resynchronisation therapy in congenital heart disease. Exp Rev Med Devices. 2008; 5: 267-271 Crossref PubMed Scopus (11) Google Scholar On the basis of the global literature and ICD interrogation in multicenter cohorts with congenital heart disease, it appeared reasonable to speculate that many inappropriate or unnecessary shocks may potentially be averted by tailored programming. This prompted our succinct “Hands On” article offering 10 programming tips in congenital heart disease. 8 Khairy P. Mansour F. Implantable cardioverter-defibrillators in congenital heart disease: 10 programming tips. Heart Rhythm. 2011; 8: 480-483 Abstract Full Text Full Text PDF PubMed Scopus (21) Google Scholar A more detailed general review of ICD programming beyond nominal settings was subsequently proposed. 9 Mansour F. Khairy P. Programming ICDs in the modern era beyond out-of-the box settings. Pacing Clin Electrophysiol. 2011; 34: 506-520 Crossref PubMed Scopus (26) Google Scholar To the Editor—Programming tips and practical programmingHeart RhythmVol. 8Issue 6PreviewI would like to offer two comments on Khairy and Mansour's well-written article on programming of implantable cardioverter-defibrillators (ICDs) in the March 2011 issue of Heart Rhythm.1 Full-Text PDF

Invited Commentary

Invited Commentary

All Patients With Hemodynamically Tolerated Postinfarction Ventricular Tachycardia Do Not Require an Implantable Cardioverter-Defibrillator

Several randomized clinical trials have been published in the last decade to evaluate the clinical efficacy of the implantable cardioverter-defibrillator (ICD) for secondary prevention of sudden cardiac arrest.1–4 However, none of those trials included patients with hemodynamically tolerated ventricular tachycardia (VT). In the largest of these trials, the Antiarrhythmics Versus Implantable Defibrillators (AVID) trial, patients with VT were included only if the VT produced syncope or if the “ejection fraction was 0.40 or less and symptoms suggesting severe hemodynamic compromise” were present.1 The Canadian Implantable Defibrillator Study (CIDS) trial included patients with VT if it produced syncope or caused presyncope or angina.2 The other 2 trials included only cardiac arrest survivors.3,4 Thus, no information is available from randomized clinical trials about outcome in patients with hemodynamically tolerated VT. Response by Callans p 1212 Despite decades of active research focused on post–myocardial infarction (MI) VT, information on the clinical outcome of sustained monomorphic VT patients is limited. Several reasons account for the limited information. First, because post-MI VT has always been considered a life-threatening condition, it has been considered unethical to leave these patients without specific antiarrhythmic therapy for group comparisons. Second, VT recurrences during follow-up have been considered in some studies together with sudden cardiac death (SCD)5 despite the fact that both events are distinctly different; the recurrence of a well-tolerated VT may require medical attention, but in most instances, the patient leaves the hospital alive and without any sequelae. Third, because ICD and catheter ablation therapy have been used increasingly in recent years, outcome information is likely to be more homogeneous in relatively old studies. Fourth, several outcome studies have included patients with a variety of sustained ventricular arrhythmias, but the prognosis of patients with ventricular fibrillation (VF) may not be the same as …

Sudden Death Prevention With Implantable Devices

The “modern” era of the treatment of ventricular tachyarrhythmias with device-based therapy may have begun in 1899, when Prevost and Battelli noted, almost as an afterthought, that direct current shock could terminate ventricular fibrillation (VF) in dogs.1 Three decades later, pioneering work in the field of defibrillation concluded that the passage of electrical current across the heart can both initiate and terminate VF.2,3 Still, little attention was paid to this phenomenon, as evidenced by Paul Dudley White’s Heart Disease , which devoted less than half a page to VF and characterized the arrhythmia as “a condition of little importance so far as we know now.”4 In 1947, the thoracic surgeon Claude Beck saved the first human life by the successful use of cardiac defibrillation in a 14-year-old boy who developed VF during a thoracic surgical procedure and went on to achieve a full recovery.5 These early accomplishments provided the foundation for the landmark work of Mirowski and Mower that ultimately led to the development of the implantable cardioverter-defibrillator (ICD) and its introduction in humans in 1980.6 Pacing may prevent sudden cardiac death due to bradyarrhythmias and in certain circumstances such as torsade de pointes associated with congenital long-QT syndrome (LQTS) and pause-dependent ventricular tachycardia (VT). Although no controlled studies exist, retrospective analyses suggest that recurrent torsade de pointes in patients with LQTS may be prevented by continuous pacing.7 Early clinical data on small numbers of patients suggested that the combination of β-adrenergic blockade plus continuous pacing reduced the number of syncopal events and the anticipated rate of sudden death in high-risk LQTS patients.8 The beneficial effects of pacing may be limited to patients with LQT2 and LQT3, in which the transmural dispersion of repolarization worsens steeply during bradycardia.9 Genotype-phenotype correlation confirms that …

Letter Regarding Article by Bokhari et al, “Long-Term Comparison of the Implantable Cardioverter Defibrillator Versus Amiodarone: Eleven-Year Follow-Up of a Subset of Patients in the Canadian Implantable Defibrillator Study (CIDS)”

To the Editor: Since the implantable cardioverter defibrillator (ICD) was introduced into clinical practice, the prospect of its widespread use has been perceived as a financial threat by many healthcare systems.1,2 The interesting study by Bokhari et al3 of the long-term efficacy of ICDs in clinical practice has relevant economic implications that the authors did not discuss. The follow-up periods reported for randomized trials on the efficacy of ICDs in secondary prevention of sudden death have been restricted previously to 3 to 5 years at most.1,4 The long-term follow-up study by Bokhari et al of Canadian Implantable Defibrillator Study (CIDS) patients at St. Michael’s Hospital in Toronto,3 who for the most part continued taking the treatment to which they were originally …

Long-term comparison of the implantable cardioverter defibrillator versus amiodarone. Eleven-year follow-up of a subset of patients in the Canadian Implantable Defibrillator Study (CIDS)

Long-term comparison of the implantable cardioverter defibrillator versus amiodarone. Eleven-year follow-up of a subset of patients in the Canadian Implantable Defibrillator Study (CIDS)

Implantable defibrillators and sudden cardiac death.

Sudden cardiac death (SCD) is among the most common causes of death in developed countries throughout the world. It is estimated that more than 3 million people die yearly from SCD, with a survival rate of less than 1%. In the United States, the Center for Disease Control recently estimated an annual incidence of 450 000 sudden deaths,1 with a survival rate of approximately 5%, although this probably is an overestimation. Although there has been a reduction in total cardiac mortality from 728 115 in 1989 to 719 456 in 1999, the percentage of deaths that are sudden has actually increased from 38% to 47%. The increase was greatest in women older than 65 years of age, from 56.3% to 63.9%. This has resulted primarily from an increase in out-of-hospital sudden deaths. There is a comparable incidence of SCD and survival rate in Western Europe.2 The magnitude of this problem can be understood by noting that SCD accounts for more deaths each year than the total number of deaths from AIDS, breast cancer, lung cancer, and stroke (Figure 1). Unfortunately, it is the first presentation of cardiac disease in 33% to 50% of patients and is 3 times as common in men than in women. Figure 1. Magnitude of the problem of sudden cardiac arrest. Coronary artery disease, with or without myocardial infarction, is by far the most common underlying disease for SCD in the western world, being responsible for approximately 75% of all SCDs.3,4 Cardiomyopathies (dilated and hypertrophic) and primary electrical heart disease account for most of the remainder. The two most important risk factors for SCD (ie, those with highest predictive value) are left ventricular ejection fraction (LVEF) less than 40% and clinical congestive heart failure.3,4 These are followed by significant ventricular arrhythmias (particularly …

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

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. 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. 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.

The Key to Unraveling the Mystery of Mortality in Heart Failure

Heart failure (HF) is a growing public health problem in the United States. Nearly 5 million Americans suffer from HF, and an estimated 550 000 new cases of HF are diagnosed each year.1 HF is the No. 1 discharge diagnosis in patients ≥65 years of age and results in a substantial burden on healthcare expenditures. It is estimated that in 2001, more than $24 billion was spent as direct cost for the care of patients with HF.1 Furthermore, HF is associated with a significant increase in morbidity and mortality. See p 1764 Although considerable progress has been made in our approach to the pharmacological management of patients with HF, most patients remain at increased risk of cardiac death. To further improve outcomes in patients with HF, newer therapeutic modalities, including devices such as biventricular pacemaker, automatic internal cardioverter-defibrillators (AICDs), and left ventricular assist devices, have been increasingly utilized. Several recent randomized controlled trials have shown that such devices can indeed further improve the outcome in patients with HF.2–4 However, these devices are expensive, and their widespread or injudicious application in unselected patients with HF is likely to have a substantial impact on healthcare expenditures. On the other hand, appropriate use of device therapy in properly selected patients (who are at high risk of mortality) is essential to improve clinical outcome. Thus, there is a need to develop a strategy to accurately identify those patients with HF who are at increased risk of mortality. The paper by Vrtovec and associates5 in the present issue of Circulation provides such a strategy by showing that routinely available diagnostic tests, such as measurement of QT interval on 12-lead ECG and measurement of B-type natriuretic peptide (BNP), can indeed identify the HF patients who are at increased risk of overall mortality, …

Quality of life in the Canadian Implantable Defibrillator Study (CIDS)

Background The primary aim of this study was to compare quality-of-life outcome between patients randomized to implantable cardioverter defibrillator (ICD) therapy and patients randomized to amiodarone treatment in the Canadian Implantable Defibrillator Study (CIDS). A secondary aim was to evaluate the effects on quality-of-life outcomes of receiving shocks from the device. Methods Quality of life was assessed in 317 English-speaking participants by use of the Rand Corporation's 38-item Mental Health Inventory (MHI) and the Nottingham Health Profile (NHP). Assessments were done in the hospital at baseline and with mailed questionnaires after 2, 6, and 12 months of follow-up. Sixty-two percent of patients completed the follow-up assessments at 6 and 12 months. Results Repeated measures analysis of variance revealed significant time by treatment group interaction effect on total MHI and the psychological distress and psychological well-being sub-scales, and on 5 of the 7 NHP scales (energy, physical mobility, emotional reactions, sleep disturbance, and lifestyle impairment) (P <.05). Emotional and physical health scores were shown to improve significantly in the ICD group and were either unchanged (emotional health) or deteriorated (energy and physical mobility) in the amiodarone-treated group by means of post-hoc comparisons. Quality of life did not improve in the subgroup of patients in the ICD-treated group who received ≥5 shocks from their device. Conclusion Quality of life is better with ICD therapy than with amiodarone therapy. The beneficial quality-of-life effects from an ICD are not evident in patients who receive numerous shocks from their device. (Am Heart J 2002;144:282-9.)

Quality of life in the Canadian Implantable Defibrillator Study (CIDS)

Quality of life in the Canadian Implantable Defibrillator Study (CIDS)

Management of the patient who has been resuscitated from sudden cardiac death.

CD is a 68-year-old man who had an anterior myocardial infarction 6 months ago. Evaluation at that time demonstrated an occluded left anterior descending artery, which was successfully stented with no other significant lesions. Left ventricular ejection fraction was 35%. He had no recurrent angina or heart failure symptoms. Early one morning he lost consciousness. Paramedics verified ventricular fibrillation (VF) and provided effective defibrillation within 5 minutes; spontaneous circulation returned before transfer to the hospital. Sudden cardiac death claims 300 000 to 450 000 lives a year in the United States and represents approximately 50% of all cardiac death.1–3⇓⇓ Despite recent declines in age-adjusted cardiac mortality and sudden death risk, the overall incidence has remained relatively stable as our population ages.3 Coronary heart disease is present in the majority (70% to 80%) of patients with sudden death, but cardiac arrest is the first manifestation of this underlying process in 50%.4 Resuscitation rates are very low, averaging from 1% to 3% in most major cities.2,5⇓ There are some data to suggest that focused attempts to reduce the time to effective defibrillation, with improved training of first responders or more widespread availability of automatic external defibrillators, provide some hope for the future. It is a widely held belief that the majority of sudden death events are due to ventricular tachycardia (VT) that degenerates into VF (Figure 1).6 This idea may well reflect our greater experience in observing patients with structural heart disease and prior myocardial infarction. Acute severe ischemia may cause primary polymorphic VT even in the absence of preexisting structural heart disease. Autopsy studies document acute changes in coronary morphology (such as plaque rupture, thrombus, etc) in >50% of sudden death events.7 Severe bradyarrhythmias or electromechanical dissociation probably represent an important …

Effect of clinical risk stratification on cost-effectiveness of the implantable cardioverter-defibrillator: the Canadian implantable defibrillator study.

Three randomized clinical trials showed that implantable cardioverter-defibrillators (ICDs) reduce the risk of death in survivors of ventricular tachyarrhythmias, but the cost per year of life gained is high. A substudy of the Canadian Implantable Defibrillator Study (CIDS) showed that 3 clinical factors, age >/=70 years, left ventricular ejection fraction </=35%, and New York Heart Association class III, predicted the risk of death and benefit from the ICD. We estimated the extent to which selecting patients for ICD therapy based on these risk factors makes ICD therapy more economically attractive. Patients in CIDS were grouped according to whether they had >/=2 of 3 risk factors. Incremental cost-effectiveness of ICD therapy was computed as the ratio of the difference in mean cost to the difference in life expectancy between the 2 groups. Over 6.3 years, the mean cost per patient in the ICD group was Canadian (C) $87 715 versus $38 600 in the amiodarone group (C$1 approximately US$0.67). Life expectancy for the ICD group was 4.58 years versus 4.35 years for amiodarone, for an incremental cost-effectiveness of ICD therapy of C$213 543 per life-year gained. The cost per life-year gained in patients with >/=2 factors was C$65 195, compared with C$916 659 with <2 risk factors. The cost-effectiveness of ICD therapy varies by patient risk factor status. The use of ICD therapy in patients who have >/=2 risk factors of age >/=70 years, left ventricular ejection fraction </=35%, and NYHA class III is C$65 195 to gain a year of life.

Revascularization Versus Implantable Cardioverter-Defibrillators to Prevent Sudden Death in Patients With Severe Left Ventricular Dysfunction

Sudden death remains a dreaded consequence of coronary artery disease, and efforts to predict its incidence and to prevent its occurrence remain a major concern. A number of the challenges in management are highlighted in the article by Veenhuyzen et al1 in the present issue of Circulation . In their study, mortality and modes of death were assessed in 5410 patients with ischemic left ventricular function who were enrolled in the Studies of Left Ventricular Dysfunction (SOLVD) study.2 There were 1870 patients who had had prior coronary artery bypass grafting (CABG) and 3540 who had not had prior CABG. The SOLVD trial database is a good source for these data, both because it is large and because the cause of death (ie, whether cardiac and whether sudden or not) was established. See p 1489 The key findings of Veenhuyzen et al1 are that CABG was associated with a 25% reduction in the risk of death (from 24.3% to 18.4%) and a 46% reduction in the risk of sudden death (from 7.5% to 4.1%). These findings are independent of ejection fraction, severity of heart failure symptoms, age, and other clinical variables. In a stratified analysis by severity of left ventricular dysfunction, there was some evidence for interaction, but similar results were noted overall. Prior CABG was not associated with an alteration in the risk of death from progressive heart failure. The results were applied to a group of patients with left ventricular dysfunction from the Coronary Artery Surgery Study Registry who had not undergone surgery, offering a predicted annual rate of death of 8.2% and sudden death …

Do baseline characteristics accurately discriminate between patients likely versus unlikely to benefit from implantable defibrillator therapy?: Evaluation of the Canadian Implantable Defibrillator Study implantable cardioverter defibrillatory efficacy score in the Antiarrhythmics Versus Implantable Defibrillators Trial

Objective Our purpose was to evaluate whether baseline characteristics predictive of implantable cardioverter defibrillator (ICD) efficacy in the Canadian Implantable Defibrillator Study (CIDS) are predictive in the Antiarrhythmics Versus Implantable Defibrillators (AVID) Trial. Background ICD therapy is superior to antiarrhythmic drug use in patients with life-threatening arrhythmias. However, identification of subgroups most likely to benefit from ICD therapy may be useful. Data from CIDS suggest that 3 characteristics (age ≥70 years, ejection fraction [EF] ≤0.35, and New York Heart Association class >II) can be combined to reliably categorize patients as likely (≥2 characteristics) versus unlikely to benefit (<2 characteristics) from ICD therapy. Methods The utility of the CIDS categorization of ICD efficacy was assessed by Kaplan-Meier analysis and Cox hazards modeling. The accuracy of the CIDS score was formally tested by evaluating for interaction between categorization of benefit and treatment in a Cox model. Results ICD therapy was associated with a significantly lower risk of death in the 320 patients categorized as likely to benefit (relative risk [RR] 0.57, 95% confidence interval [CI] 0.37-0.88, P =.01) and a trend toward a lower risk of death in the 689 patients categorized as unlikely to benefit (RR 0.70, 95% CI 0.48-1.03, P =.07). Categorization of benefit was imperfect, as evidenced by a lack of statistical interaction (P =.5). Although 32 of the 42 deaths prevented by ICD therapy in AVID were in patients categorized as likely to benefit, all 42 of these patients had EF values ≤0.35. Neither advanced age nor poorer functional class predicted ICD efficacy in AVID. Conclusion Of the 3 characteristics identified to predict ICD efficacy in CIDS, only depressed EF predicted ICD efficacy in AVID. Thus physicians faced with limited resources might elect to consider ICD therapy over antiarrhythmic drug use in patients with severely depressed EF values. (Am Heart J 2001;141:99-104.)

Meta-analysis of the implantable cardioverter defibrillator secondary prevention trials. AVID, CASH and CIDS studies. Antiarrhythmics vs Implantable Defibrillator study. Cardiac Arrest Study Hamburg . Canadian Implantable Defibrillator Study.

Three randomized trials of implantable cardioverter defibrillator (ICD) therapy vs medical treatment for the prevention of death in survivors of ventricular fibrillation or sustained ventricular tachycardia have been reported with what might appear to be different results. The present analysis was performed to obtain the most precise estimate of the efficacy of the ICD, compared to amiodarone, for prolonging survival in patients with malignant ventricular arrhythmia. Individual patient data from the Antiarrhythmics vs Implantable Defibrillator (AVID) study, the Cardiac Arrest Study Hamburg (CASH) and the Canadian Implantable Defibrillator Study (CIDS) were merged into a master database according to a pre-specified protocol. Proportional hazard modelling of individual patient data was used to estimate hazard ratios and to investigate subgroup interactions. Fixed effect meta-analysis techniques were also used to evaluate treatment effects and to assess heterogeneity across studies. The classic fixed effects meta-analysis showed that the estimates of ICD benefit from the three studies were consistent with each other (P heterogeneity=0.306). It also showed a significant reduction in death from any cause with the ICD; with a summary hazard ratio (ICD:amiodarone) of 0.72 (95% confidence interval 0.60, 0.87;P=0.0006). For the outcome of arrhythmic death, the hazard ratio was 0.50 (95% confidence interval 0.37, 0.67;P<0.0001). Survival was extended by a mean of 4.4 months by the ICD over a follow-up period of 6 years. Patients with left ventricular ejection fraction < or = 35% derived significantly more benefit from ICD therapy than those with better preserved left ventricular function. Patients treated before the availability of non-thoracotomy ICD implants derived significantly less benefit from ICD therapy than those treated in the non-thoracotomy era. Results from the three trials of the ICD vs amiodarone are consistent with each other. There is a 28% reduction in the relative risk of death with the ICD that is due almost entirely to a 50% reduction in arrhythmic death.

Therapeutic decision tree for patients with sustained ventricular tachyarrhythmias or aborted cardiac arrest: a critical review of the antiarrhythmics versus implantable defibrillator trial and the Canadian implantable defibrillator study

Antiarrhythmic drugs, mainly amiodarone and sotalol, radiofrequency catheter ablation, and the implantable cardioverter defibrillator (ICD) are the 3 therapeutic options in patients with sustained ventricular tachycardia (VT) or ventricular fibrillation (VF). Idiopathic VT, incessant VT, frequently recurring, hemodynamically stable VT, and VT based on bundle branch reentry, are candidates for radiofrequency catheter ablation. Patients with high-risk ventricular tachyarrhythmias should receive ICDs as initial therapy. Two studies, the Antiarrhythmics Versus Implantable Defibrillator trial (AVID) and the Canadian Implantable Defibrillator Study (CIDS) have tried to approach the problem of these high-risk ventricular tachyarrhythmias. Although at 3 years, the ICD in AVID demonstrated a significant relative risk reduction over amiodarone of 31.5%, CIDS could not duplicate this finding. At 3 years, the relative risk reduction conferred by the ICD over amiodarone in CIDS was only 13.7%. A careful analysis of both studies suggests that CIDS was insufficiently powered to demonstrate statistically significant benefits similar to those shown by AVID, and furthermore, seemed to include an undetermined number of low-risk VT patients. The problem in the CIDS trial in this regard was the recruitment of patients in whom the inclusion criteria were met by the arrhythmias induced during the electrophysiology stimulation study, but which did not exist in real life. In addition CIDS included 14% of patients with (1) undocumented syncope and inducible monomorphic sustained VT; or (2) long runs of spontaneous nonsustained VT. Under these circumstances, the therapeutic implications of AVID remain unchallenged.

Canadian implantable defibrillator study: What does it mean after the antiarrhythmics versus implantable defibrillators trial?

Canadian implantable defibrillator study: What does it mean after the antiarrhythmics versus implantable defibrillators trial?

Arrhythmias in Heart Failure.

Cardiac arrhythmias are very common in the setting of heart failure, with atrial and ventricular arrhythmias often present in the same patient. The risk and the benefit of antiarrhythmic therapies are still a matter of debate. Class I antiarrhythmic drugs should be avoided in patients with heart failure, cardiac ischemia, or previous myocardial infarction. Beta-blocker agents reduce morbidity and decrease mortality in patients suffering from moderate to severe heart failure. Amiodarone may be beneficial in patients with advanced heart failure and increased resting heart rates. This class III drug may be effective to suppress episodes of atrial fibrillation but can also be beneficial in reducing ventricular response by slowing atrioventricular conduction during chronic atrial fibrillation. Implantable cardioverter-defibrillators (ICDs) markedly reduce sudden cardiac death in patients with ventricular tachycardia or ventricular fibrillation. In patients with advanced heart failure, however, the ICD may not markedly extend survival. Recently analyzed data from the Canadian Implantable Defibrillator Study (CIDS), Antiarrhythmics Versus Implantable Defibrillators (AVID) registry, Multicenter Unsustained Tachycardia Trial (MUSTT), and Multicenter Automatic Defibrillator Implantation Trial (MADIT) have consistently shown that it is the sickest patient who benefits the most from ICD therapy. Patients with markedly depressed ejection fraction (<30%), poor New York Heart Association functional class, and advanced age have been identified as those who really need ICD therapy. Studies of implantable cardioverter-defibrillators in patients with moderate to severe heart failure have been launched and will provide necessary answers to the question of whether a reduction in sudden death will translate into a reduction of all-cause mortality. For patients resuscitated from sustained ventricular tachycardia or ventricular fibrillation, an ICD or, in some cases, amiodarone should be considered. Catheter or surgical ablation can be considered for selected patients with ventricular tachycardia.