Implantable cardioverter-defibrillator therapy in survivors of out-of-hospital sudden cardiac death without inducible arrhythmias

Survivors of ventricular fibrillation have persistent cardiovascular risk factors late in follow-up

OBJECTIVE

Implantable cardioverter-defibrillators (ICDs) prevent arrhythmic death, but do not modify disease progression. The prevalence of persistent cardiovascular risk factors in patients receiving an ICD and their adherence to optimal pharmacological therapy at late follow-up is unknown. The aim of this study was to assess the prevalence of cardiovascular and specific sudden cardiac arrest (SCA) risk factors, and the pharmacological treatment in ICD recipients who survived SCA caused by ventricular fibrillation (VF).

DESIGN

Cross-sectional study. A total of 100 consecutive ICD patients who survived SCA due to documented VF, not due to a transient or reversible cause or an arrhythmogenic disease, were interviewed and examined at the routine outpatient clinic.

RESULTS

The mean age of the patients was 60 ± 11 years, and they were analysed at a median interval of 1092 days after SCA. The majority of patients had coronary artery disease. The New York Heart Association class at the time of implantation was ≥ II in 62%. A single chamber device was used in 49% and a resynchronization device in 12%. At the routine control, the most prevalent risk factors were overweight or obesity (63%), hypertension (41%), and smoking (16%). Pharmacological therapy was suboptimal in 18-32% of the patients. Eight per cent of the patients had known diabetes and 29% had elevated HbA1c levels. While only 7% had pre-existing overt heart failure, 43% had N-terminal pro-brain natriuretic peptide levels ≥ 100 pmol/l. High sensitivity C-reactive protein was ≥ 3 mg/l in 52% of the patients. Family history was positive for sudden cardiac death (SCD) in 46% of the patients.

CONCLUSIONS

Despite regular medical consultation, a large proportion of the patients had persistent cardiovascular risk factors and were often suboptimally treated. Unexpectedly, latent heart failure and unrecognized diabetes are observed in a large proportion of the patients, as well as elevated inflammatory markers. Genetic analysis may be rewarding, as 46% of the patients had a family history of SCD. Full medical attention, optimizing drug therapy, and counselling of these patients is necessary.

Clinical review: beyond immediate survival from resuscitation-long-term outcome considerations after cardiac arrest

A substantial body of literature concerning resuscitation from cardiac arrest now exists. However, not surprisingly, the greater part concerns the cardiac arrest event itself and optimising survival and outcome at relatively proximal time points. The aim of this review is to present the evidence base for interventions and therapeutic strategies that might be offered to patients surviving the immediate aftermath of a cardiac arrest, excluding components of resuscitation itself that may lead to benefits in long-term survival. In addition, this paper reviews the data on long-term impact, physical and neuropsychological, on patients and their families, revealing a burden that is often underestimated and underappreciated. As greater numbers of patients survive cardiac arrest, outcome measures more sophisticated than simple survival are required.

Update on cardiac resuscitation for sudden death: International Guidelines 2000 on Resuscitation and Emergency Cardiac Care

Cardiopulmonary resuscitation developed over the past one half century largely from empiric science and consensus opinions and recommendations. Treatment algorithms and protocols were originally developed to summarize existing recommendations for systematic and regimented use by a heterogenous group of health care providers. Now, resuscitation science and health care teams are focusing on major issues and continuing questions as sudden death rates remain undaunted and the population at risk is rapidly increasing. For the first time, the international resuscitation community has developed an international consensus on Guidelines for Resuscitation and Emergency Cardiac Care. More than 400 basic scientists, clinical trial investigators, and educators defined common priority and scientific areas during the Evidence Evaluation International Meeting in 1999. The science of resuscitation and emergency cardiac care was reviewed for evidence-based support in randomized clinical trials. In 2000, this review was used as a foundation to structure international guidelines. The participants from seven resuscitation councils and foundations realized that regional differences in systems may exist, but the underlying science should be the same. Presented in this article are some of the major issues and controversies discussed in adult advanced cardiac life support, primarily focusing on the major problem of prehospital adult cardiac arrest.

Navigation in the mega-trials waters: reflections on the Multicenter Automatic Defibrillator Implantation Trial and the Antiarrhythmics Versus Implantable Defibrillators Study

Today, cardiology seems to be driven by mega-trials and meta-analyses. Guidelines published by scientific and professional cardiovascular societies, such as the American Heart Association, the American College of Cardiology, and the European Society of Cardiology, follow the rules of evidence-based medicine. Such evidence is not always sufficiently conclusive to practice clinically helpful medicine. Sometimes, relatively small trials, such as the Multicenter Automatic Defibrillator Implantation Trial and the Antiarrhythmics Versus Implantable Defibrillators study, may be taken as guides for current clinical decisions and as inspiration for future investigations. Large mega-trials with a great lack of homogeneity among the recruited patients are less important for clinically helpful medicine than studies enrolling well-defined, high-risk patients. It is probably important to acknowledge that the best possible treatment for many patients with ventricular tachyarrhythmias remains obscure. Among these situations are the following: (1) sustained ventricular tachycardia (VT) in patients without coronary artery disease; (2) sustained, nonsyncopal VT in patients with coronary artery disease and left ventricular dysfunction; (3) post myocardial infarction survivors with an ejection fraction < or = 35%, frequent/complex ventricular arrhythmias, depressed heart rate variability, and inducible sustained ventricular tachyarrhythmias during electrophysiologic study. Many studies are being conducted to add light where uncertainty exists, but probably only a few will contribute to the practice of clinically helpful medicine, although some will be used to produce meta-analysis to sustain evidence-based medicine.

Cardiac death and stored electrograms in patients with third-generation implantable cardioverter-defibrillators

OBJECTIVES

We sought to utilize terminal stored intracardiac electrograms (EGMs) to study the electrophysiologic events that accompany mortality in patients with third-generation implantable cardioverter-defibrillators (ICDs).

BACKGROUND

Despite their ability to effectively terminate ventricular tachyarrhythmias, cardiac mortality in patients with ICDs remains high. The mechanisms and modes of death in these patients are not well understood.

METHODS

We retrospectively analyzed clinical data and stored EGMs from patients enrolled in the clinical trial of the Ventritex Cadence ICD. Of the 1,729 patients 119 died during 6 years of follow-up. The final recorded EGM was reviewed. Postimplant EGMs as well as 50 control EGMs were used to define normal EGM characteristics.

RESULTS

There were 36 noncardiac deaths (30%) and 83 cardiac deaths (70%). Of the cardiac deaths, 55 (66%) were nonsudden and 28 (34%) were sudden. When cardiac deaths were analyzed, 46 (55%) had no stored EGMs within 1 h of death, implying that the deaths were not directly related to tachyarrhythmias. In 37 cardiac deaths (18 nonsudden, 19 sudden), stored EGMs were present within 1 h of death. In these 37 deaths, the final EGM recorded was wide (>158 ms) in 33 (89%). Wide EGMs were interpreted as ventricular tachycardia in 27 and ventricular fibrillation in 6. In 13 of the 33 patients (39%) with wide EGMs, therapy was not delivered by the ICD, as it incorrectly detected a spontaneous termination of the arrhythmia. EGMs were significantly wider if recorded within 1 h, as compared with those recorded from 1 to 48 h before death (261+/-124 vs. 181+/-93 ms, p=0.04).

CONCLUSIONS

Only 37 patients (31%) who died after placement of an ICD had a stored EGM within 1 h of the time of death, suggesting that the majority of deaths (69%) were not the immediate result of a tachyarrhythmia. When EGMs were recorded, they were wide in 89% of patients. These wide EGMs most likely represent intracardiac recordings of electromechanical dissociation. Thus, of the 119 deaths, 112 (94%) were not the immediate result of a tachyarrhythmia.

Primary prevention of sudden cardiac death in heart failure: will the solution be shocking?

Sudden cardiac death (SCD) may occur in as many as 40% of all patients who suffer from heart failure. This review describes the scope of the problem, risk factors for SCD, the effect of medications used in heart failure on SCD and the potential effect of the implantable cardioverter-defibrillator in primary prevention.

Implantable cardioverter-defibrillator therapy: influence of left ventricular function on long-term results

The degree of left ventricular impairment in an acknowledged important prognostic marker of long-term outcome for patients being evaluated for implantation of cardioverter-defibrillators. Just how left ventricular function impacts freedom from all-cause mortality, as well as from sudden death and cardiac death, is a subject of current major debate, and is analyzed hereunder from a large, recent multicenter ICD patient cohort. The multicenter database consists of data from 361 patients receiving implantable cardioverter-defibrillators for standard indications, that is, documented episodes of ventricular fibrillation or sustained ventricular tachycardias with poor hemodynamic toleration. Data were collected from 1988 to 1995 at three centers in Germany. Two-hundred and three patients (56%) had a left ventricular ejection fraction (LVEF) > 0.30 (group I), and 158 patients (44%) had a LVEF < or = 0.30 respectively (group II). The mean follow-up was 23.9 months (range 3-98 months). Overall survival at 5 years for group II patients was lower, as expected, at 74.1% versus 94.2%, respectively (P < 0.0001). Mortality was higher for each different cause of death in group II patients than in Group I: sudden arrhythmic deaths, 5 versus 1 (P < 0.048); nonsudden cardiac deaths, 16 versus 5 (P < 0.002); noncardiac deaths, 7 versus 2 (P < 0.03). Group II patients received a higher rate of at least one presumably appropriate shock at 86 (54.4%) versus 89 (43.8%) in group I (P < 0.05). However (and somewhat surprisingly), neither the time from ICD implantation to death, comparing only the patients who died, nor the event-free probability of appropriate shocks due to very rapid, sustained ventricular arrhythmias (> 230 beats/min), including a presumed risk of sudden arrhythmogenic death, differed between groups I and II. Sudden cardiac death was only marginally affected by LVEF (group I, 1.5% actuarial, 5-year survival 99.5%; group II, 3.1% and 95.8%, respectively). Therefore, the lower overall survival in ICD patients with LVEF < or = 0.30 resulted mainly from causes of death that cannot be directly influenced by cardioverter-defibrillator therapy. However, because group II patients had a far higher incidence of at least one ventricular tachyarrhythmia terminated by ICD shocks than group I patients, they also probably derived benefit from ICD therapy.

Current concepts in electrical defibrillation

The electrical defibrillator has been proven to be a life-saving device in the treatment of cardiac arrest due to ventricular tachycardia or ventricular fibrillation. An understanding of the physiology and technology behind this device is useful for providers of emergency care. In this article, we review the current concepts in electrical defibrillation and briefly discuss the developmental history. The physiology and the technical considerations will make up the bulk of the discussion. The latest developments in electrical defibrillation also will be reviewed.

Influence of patient characteristics in the selection of patients for defibrillator implantation (the AVID Registry). Antiarrhythmics Versus Implantable Defibrillators

The Antiarrhythmics Versus Implantable Defibrillators (AVID) trial is a prospective, randomized study of treatment for life-threatening ventricular arrhythmias. Patients who are eligible for the main trial but who are not enrolled for any reason are followed in a registry. The objective of the present study was to determine whether there are identifiable patient characteristics among these registry patients that may influence whether a patient is treated with an implantable defibrillator. The 914 patients in the registry were divided into 2 groups according to whether the primary treatment was an implantable defibrillator. The mean age of defibrillator patients was 60 years, compared with 65 years in the nondefibrillator group (p <0.001). Only 11.2% of defibrillator recipients were minorities, whereas the percentage of minorities in the nondefibrillator group was 18.7% (p <0.003). A history of recurrent ventricular fibrillation was more likely in the group treated with defibrillators (8.9% vs 4.4%, p <0.01), whereas a history of atrial fibrillation or diabetes mellitus were both significantly more likely in the nondefibrillator group. Among defibrillator patients, a higher proportion had ventricular fibrillation as the index arrhythmia; patients with ventricular tachycardia were significantly more likely to be treated without devices. In this prospective but nonrandomized cohort of patients treated for life-threatening ventricular arrhythmias, older age, minority status, and comorbidity reduced the chances that a patient would be treated with a defibrillator.

Long-term follow-up of patients treated with implantable cardioverter defibrillators in a Danish centre. Accurrence ICD therpay and patient survivors

The aim of the this prospective follow-up study was to evaluate long-term survival and implantable cardioverter-defibrillator (ICD) therapy for ventricular tachyarrhythmias in patients treated with an ICD in a Danish centre. A total of 140 consecutive patients (112 men), of which 70.7% had coronary artery disease, received an ICD at Skejby University Hospital between March 1989 and October 1996. Mean age was 55.6 +/- 14.6 years (range 14-78 years). After implantation, 136 of the patients were followed for a median (range) of 17.7 (0.4-74.1) months. Survival, mode of death and incidence of appropriate ICD therapy and therapy due to potential life-threatening ventricular tachyarrhythmia were the main outcome measures. Kaplan-Meier plots representing total survival, cardiac death, sudden cardiac death and first episode of ICD therapy are presented. After 1, 2, 3 and 4 years, respectively, the cumulative incidences of death were 9, 18, 20 and 24%, of cardiac death 4, 11, 14 and 18%, and of sudden cardiac death 2, 3, 6 and 6%. The cumulative incidences of appropriate therapy after 1, 2, 3 and 4 years were 47, 56, 66 and 80%, respectively. The cumulative incidences of cardiac death after the first episode of appropriate therapy were 9, 11, 15 and 20% after 1, 2, 3 and 4 years, respectively. The occurrence of ICD therapy and patient survival in the present study population treated with ICD at a Danish centre was comparable to results published previously from other larger centres. The rate of sudden cardiac death was low and most of our patients received appropriate ICD therapy during follow-up, indicating correct patient selection and probable benefit of the ICD device.

Characterization of spontaneous recurrent ventricular arrhythmias detected by electrogram-storing defibrillators in sudden cardiac death survivors with no inducible ventricular arrhythmias at baseline electrophysiologic testing

This retrospective study characterized the recurring ventricular arrhythmias with an electrogram-storing defibrillator in survivors of sudden cardiac death who had no inducible sustained ventricular arrhythmias at baseline electrophysiologic testing (EPS). The study group was composed of 24 selected patients with documented ventricular fibrillation (VF) without need of revascularization or chronic antiarrhythmic therapy. The EPS protocol usually consisted of three extrastimuli at two drive cycles at two right ventricular sites. Nonischemic cardiomyopathy was the most frequent structural abnormality (n = 11) followed by coronary artery disease (n = 7). The mean ejection fraction was 0.37 +/- 0.13. Cardiac status did not appear to change during a mean follow-up period of 16.4 +/- 12.5 months, and eight (33%) patients received appropriate shocks in that time period. On the basis of intracardiac electrograms, 7 (88%) patients experienced VF and 1 (12%) patient had ventricular tachycardia as the first recurring arrhythmia. Four patients had additional recurrences and all were VF episodes. VF was usually present from the onset of the arrhythmia. In addition, 9 (38%) patients had nonsustained ventricular arrhythmias that were solely VF in 6 (67%). In conclusion, VF of sudden onset was the most frequent recurring sustained ventricular arrhythmia in this group.

Drugs versus devices: contemporary practice in light of contemporary trials

In years past, the secondary prevention of life-threatening ventricular arrhythmias was limited to empiric drug therapy. In close temporal proximity to the birth of electrophysiologic study-guided treatment strategies to manage these arrhythmias, devices to convert arrhythmias were envisioned and designed. Now, advanced generation implantable defibrillators provide synchronized, low-energy cardioversion, antitachycardia pacing, and pacing support for bradycardia. Over the past decade and half, this technology that was once applied as a therapy of last resort has evolved and emerged as a therapy of first choice. Recently, however, enthusiasm for drug treatment strategies has also increased, especially the use of amiodarone. Most experts now agree that drug therapy chosen by electrophysiologic study guidance provides superior survival compared to the empiric use of Class I drugs, as long as a drug that suppresses arrhythmia inducibility is found. The empiric use of amiodarone and beta blockers may also improve outcome. This review examines some of the recent clinical trials utilizing pharmacologic and nonpharmacologic methods. The importance of ongoing and future clinical trials is emphasized.

Treatment of ventricular arrhythmias in older adults

OBJECTIVE

To review the prognosis and management of ventricular arrhythmias (VA) in persons with and without heart disease with emphasis on older adults.

DATA SOURCES

A computer-assisted search of the English language literature (MEDLINE database) followed by a manual search of the bibliographies of pertinent articles.

STUDY SELECTION

Studies on the prognosis and management of VA in persons with and without heart disease were screened for review. Studies in older people and recent studies were emphasized.

DATA EXTRACTION

Pertinent data were extracted from the reviewed articles. Emphasis was on studies involving the older persons. Relevant articles were reviewed in depth.

DATA SYNTHESIS

Available data about the prognosis and management of VA in persons with and without heart disease, with emphasis on studies involving older people, were summarized.

CONCLUSIONS

VA in older persons without heart disease should not be treated with antiarrhythmic drugs. Class I antiarrhythmic drugs should not be used to treat VA in older persons with heart disease. Beta blockers should be used to treat complex VA in older persons with ischemic or nonischemic heart disease if there are no contraindications to beta blocker therapy. The use of amiodarone in treating complex VA should be reserved for life-threatening ventricular tachyarrhythmias in older persons who cannot tolerate or who do not respond to beta blockers. VA associated with congestive heart failure should be treated with angiotensin converting enzyme inhibitors. If older patients have life-threatening recurrent ventricular tachycardia or ventricular fibrillation resistant to antiarrhythmic drugs, invasive intervention should be performed. The automatic implantable cardioverter-defibrillator is recommended in older patients who have medically refractory sustained ventricular tachycardia or ventricular fibrillation.

Comparison of defibrillator therapy and other therapeutic modalities for sustained ventricular tachycardia or ventricular fibrillation associated with coronary artery disease

Outcomes of 282 patients referred to the arrhythmia service at Montefiore Medical Center for sustained ventricular tachycardia (n = 214) or ventricular fibrillation (n = 68) associated with coronary artery disease were analyzed retrospectively. All patients underwent serial drug trials by electrophysiologic testing and Holter monitoring. Sixty-eight patients who did not respond to drug therapy were treated with implantable cardioverter-defibrillators (ICD group), and 214 patients were treated with other methods guided by electrophysiologic testing and Holter monitoring (non-ICD group). The non-ICD group included 49 patients who responded to drug therapy as judged by electrophysiologic testing, as well as patients who did not respond and were not treated with defibrillator therapy for various reasons. Ten patients died in the hospital (2 patients in the ICD group, 8 in the non-ICD group). Actuarial survival rates free of total cardiac death at 1, 2, and 3 years were, respectively, 94%, 87%, and 85% in the ICD group, and 82%, 78%, and 73% in the non-ICD group (p = NS). Survival rates free of total death at 1, 2, and 3 years were 90%, 82%, and 76% in the ICD group, and 82%, 76%, and 70% in the non-ICD group, respectively (p = NS). Survival rates free of total cardiac and total deaths of 49 patients treated with an effective regimen determined by electrophysiologic testing were not significantly different from those of the ICD group. This retrospective study suggests that outcomes of patients treated with ICDs may not be dramatically different from those of patients treated with other methods guided primarily by electrophysiologic testing.(ABSTRACT TRUNCATED AT 250 WORDS)

Continuous monitoring of acute myocardial ischemia by the implantable cardioverter defibrillator

The present generation of implantable cardioverter defibrillators (ICDs) provides a very effective device for monitoring and treating life-threatening ventricular tachyarrhythmia. Patients at risk of sudden cardiac death who are directed to this form of treatment usually have severe coronary artery disease, previous myocardial infarction, and low ejection fraction. Progression of the underlying heart disease predisposes these patients to subsequent ischemic events, including symptomatic and asymptomatic myocardial ischemia and reinfarction, which carry a substantial risk of fatal ventricular proarrhythmia. Multipolar lead configurations presently available in the ICD appear to be effective in assessing acute myocardial ischemia as induced by exercise testing or transient coronary artery occlusion. Continuous monitoring of myocardial ischemia (COMONI) by a sophisticated, multimodal ICD appears to be feasible, may offer the means to closely supervise progression and various complications of the underlying heart disease, and may help to guide automatic or interactive antiischemic treatment.

Antiarrhythmic drugs versus implantable defibrillators: the need for a randomized controlled study

The implantable cardiac defibrillator was first used in 1980 and has gained widespread acceptance. However, no randomized controlled trials have been reported that compare the implantable cardiac defibrillator with antiarrhythmic drugs. Most published studies have used historical control subjects or nonrandomized concurrent patients for comparison with patients who received an implantable defibrillator. To reduce bias, studies are needed that compare therapies randomized between antiarrhythmic drugs and implantable defibrillators. The Antiarrhythmics Versus Implantable Defibrillators (AVID) Study was designed to evaluate the nonthoracotomy, tiered-therapy implantable defibrillator compared with drug therapy (amiodarone or sotalol). Patients are eligible for randomization if they have a history of recent cardiac arrest caused by ventricular fibrillation or have hemodynamically serious ventricular tachycardia. A pilot study to enroll 200 patients began on June 1, 1993, before the start of the main study of 1000 patients. Analysis of the main study by intention to treat will assess the primary endpoint of total mortality.

The impact of implantable cardioverter defibrillator therapy on health care systems

Implantable cardioverter defibrillators (ICDs) are now widely used for the secondary prevention of sudden cardiac death and are being offered as a primary preventive therapy. This technology has potential for significant fiscal impact on health care budgets. Technologic innovation will result in more complex devices that are more effective and better accepted by patients and physicians. The clinical impact of these devices will be predicated, in part, by absolute survival benefits but also by their relative advantages over alternative therapies in terms of survival, safety, morbidity, quality of life, and cost. The impact on public health will depend on the effectiveness of screening methods for identification of populations likely to benefit from primary prevention. Risk stratification algorithms are now being tested in several ongoing clinical trials. Dilution of benefit by competing illnesses may occur to different extents in individual patient populations. The economic impact is predicated on the future cost of ICD systems, limitation of hospitalization costs associated with this therapy, and accurate prospective stratification in primary prevention populations. Cost efficacy analyses and quality of life assessment in ongoing and future clinical trials are essential to the development of this therapy and its diffusion into different health care systems. Achievement of clinical benefits, functional independence, and a return to gainful employment by patients will be important determinants of the support lent by health care systems to the dissemination of this therapy.