Recent primary prevention implantable cardioverter defibrillator trials

PURPOSE OF THE REVIEW: The aim of this article is to summarize the most relevant findings of recently published trials on prophylactic implantable cardioverter defibrillator therapy. RECENT FINDINGS: A number of important randomized clinical trials on the efficacy of prophylactic implantable cardioverter defibrillator therapy in patients deemed to be at high risk for ventricular tachyarrhythmias have recently reported their results. Patients with chronic ischemic cardiomyopathy, a long history of heart failure, and an ejection fraction of 0.30 or below benefit from preventive device therapy and are thus candidates for prophylactic defibrillator implantation. For this purpose, a single chamber device appears to be appropriate since there have been no prospective studies showing convincing clinical benefit by adding an atrial lead. Prophylactic implantable cardioverter defibrillator therapy should not be used in patients with recent myocardial infarction. There is convincing evidence from one trial that benefit from the defibrillator in coronary patients accrue after a considerable time has elapsed from the most recent infarct, presumably at least 6 months or perhaps longer. Finally, in patients with chronic dilated non-ischemic cardiomyopathy and a left ventricular ejection fraction of 0.35 or below, there is also benefit from prophylactic implantable cardioverter defibrillator therapy. SUMMARY: Taken together, these trials allow an evidence-based approach to primary prevention of sudden cardiac death in patients with both ischemic and non-ischemic cardiomyopathy.     

Implications for present and future applications of the implantable cardioverter-defibrillator resulting from the use of a simple model of cost efficacy.

OBJECTIVE--To develop a model to assess the cost-efficacy of the implantable cardioverter defibrillator to prevent sudden death. The model must be sufficiently flexible to allow the use of cost and survival figures derived from different sources. SETTING--The study was conducted in a teaching hospital department of cardiology with experience of 40 implantable cardioverter defibrillator implants and a large database of over 500 survivors of myocardial infarction. PROCEDURE--The basic costs of screening tests, stay in hospital, and purchase of implantable cardioverter defibrillators were derived from St George's Hospital during 1991. To assess the cost-efficacy of various strategies for the use of implantable cardioverter defibrillators, survival data taken from published studies or from our own database. Implications of the national cost of the various strategies were calculated by estimating the number of patients a year requiring implantation of a defibrillator if the strategy was adopted. RESULTS--Use of implantable cardioverter defibrillators in survivors of cardiac arrest costs between 22,400 pounds and 57,000 pounds for each year of life saved. Most of the strategies proposed by the current generation of implantable cardioverter defibrillator trials have cost efficacies in the same range, and adoption of any one of these strategies in the United Kingdom could cost between 2 million pounds and 100 million pounds a year. Future technical and medical developments mean that cost-efficacy may be improved by up to 80%. Due to the limitations of screening tests currently available restriction on the use of implantable cardioverter defibrillators to those groups where it seems highly cost-effective will result in a small impact on overall mortality from sudden cardiac death. CONCLUSION--Present and possible future applications of the implantable cardioverter defibrillator seem expensive when compared with currently accepted treatments. Technical and medical developments are, however, likely to result in a dramatic improvement in cost efficacy over the next few years.     

Moderate exercise training improves functional capacity, quality of life, and endothelium-dependent vasodilation in chronic heart failure patients with implantable cardioverter defibrillators and cardiac resynchronization therapy.

BACKGROUND: The objective of this study was to determine the effects of a moderate exercise training program on functional capacity, quality of life, and hospital readmission rate in chronic heart failure patients with implantable cardioverter defibrillators and cardiac resynchronization therapy. METHODS AND RESULTS: We studied 52 men (mean age 55+/-10 years, ejection fraction 31+/-7%) in chronic heart failure II (n=29) and III (n=23) NYHA functional class with ischemic cardiomyopathy who received implantable cardioverter defibrillators with or without cardiac resynchronization therapy. Patients were randomized into two groups. Group T (n=30 patients, 15 implantable cardioverter defibrillator, 15 implantable cardioverter defibrillator+cardiac resynchronization therapy) underwent a supervised exercise training program at 60% of peak VO2 three times a week for 8 weeks. Group C (n=22 patients, 12 implantable cardioverter defibrillator, 10 implantable cardioverter defibrillator+cardiac resynchronization therapy) avoided physical training. At 8 weeks, only trained patients had improvements in peak VO2 (P<0.01 versus C), endothelium-dependent dilatation of the brachial artery (P<0.001 versus C) and quality of life (P<0.001 versus C). Among trained patients, those with cardiac resynchronization therapy had greater improvements in peak VO2 and quality of life. During the follow-up (24+/-6 months), eight controls had sustained ventricular tachycardia requiring hospital readmission, while no trained patients had adverse events (log rank 8.56; P<0.001). The improvement in peak VO2 was correlated with the improvement in endothelium-dependent dilatation (r=0.65). CONCLUSION: Moderate exercise training is safe and has beneficial effects after implantable cardioverter defibrillator implantation, especially when cardiac resynchronization therapy is present. These effects are associated with improvement in quality of life and outcome.     

Long-term outcome of pharmacological and nonpharmacological treatment for ventricular arrhythmias

Recent advances of nonpharmacological therapy such as catheter ablation and implantable cardioverter defibrillator and lessons from the Cardiac Arrhythmia Suppression Trial(CAST) have changed the strategy for ventricular arrhythmias. The safety and efficacy of radiofrequency catheter ablation of symptomatic sustained monomorphic ventricular tachycardia without structural heart disease has made ablation the firstline curative therapy. In idiopathic ventricular fibrillation such as Brugada syndrome, an implantable cardioverter defibrillator is the most effective treatment to prevent sudden cardiac death. In patients with asymptomatic ventricular tachyarrhythmias in heart failure, class I antiarrhythmic drugs should be avoided due to proarrhythmic and negative inotropic effects that may be responsible for increased mortality in some trials. In such patients, amiodarone and beta-blocker may reduce sudden cardiac death. For patients with sustained ventricular tachycardia or ventricular fibrillation in heart failure, amiodarone or implantable cardioverter defibrillator should be considered. In comparison with amiodarone, implantable cardioverter defibrillator markedly reduced sudden death in ventricular tachycardia and ventricular fibrillation survivors in Antiarrhythmics Versus Implantable Defibriltors(AVID). Although better patient selection and clarification of mapping criteria improved the successful ablation rate in patients with structural heart disease, candidates of ablation are few. In patients with extensive structural heart disease, multiple ventricular tachycardias are often present. Catheter ablation of a single ventricular tachycardia may be only palliative. Therefore, implantable cardioverter defibrillator is the most effective treatment to prevent sudden cardiac death, with amiodarone and ablation as the adjunctive therapy to prevent frequent ventricular tachycardia. Furthermore, an implantable cardioverter defibrillator improved survival in selected patients with depressed ventricular function after myocardial infarction, who also have nonsustained and inducible sustained ventricular tachycardia in Multicenter Automatic Defibrillator Implantation Trial(MADIT) and Multicenter Unsustained Tachycardia Trial(MUSTT).     

Asymptomatic right ventricular perforation by an implantable cardioverter defibrillator lead detected by home monitoring system

Right ventricular lead perforation is a rare but serious and potentially life-threatening complication of pacemaker or defibrillator lead implantation. This report describes a patient with Brugada syndrome in whom the diagnosis of asymptomatic right ventricular perforation by an implantable cardioverter defibrillator lead was detected 12 days after implantation, thanks to a report from home monitoring system. The patient was admitted to our institution, where the lead was explanted and replaced. This case illustrates the potential lifesaving benefit of the home monitoring system in patients with implantable cardioverter defibrillator.     

Update of implantable cardioverter/defibrillator and cardiac resynchronization therapy in heart failure

PURPOSE OF REVIEW: Heart failure prevalence is reaching epidemic proportion in the United States and is associated with significant morbidity and mortality. A large proportion of the mortality is the result of sudden cardiac death (SCD). Clinical trials have demonstrated the superiority of the implantable cardioverter/defibrillator (ICD) compared with antiarrhythmic drugs for secondary prevention of sudden cardiac death. RECENT FINDINGS: Recently, several clinical trials in primary prevention of sudden cardiac death in both ischemic and nonischemic heart failure have been completed. The 2002 guidelines for implantable cardioverter/defibrillator implantation were recently released as well. Adjunct therapy consisting of antiarrhythmic drugs or radiofrequency ablation is necessary in the subset of patients with implantable cardioverter/defibrillator that have frequent or intractable ventricular arrhythmias. An emerging new therapy in the heart failure population is cardiac resynchronization therapy, which coordinates right and left ventricular pacing in a subset of patients with interventricular conduction delay. SUMMARY: Several randomized clinical trials have demonstrated improvements in heart failure-related symptoms, exercise tolerance, and reversal of ventricular remodeling. Meta-analysis of these trials has also demonstrated mortality benefit. Patient selection, left ventricular pacing site, and optimal device programming are issues that need further investigation. Recent trials have also studied the compatibility between cardiac resynchronization therapy and implantable cardioverter/defibrillator as a single device. Finally, the DAVID trial has raised concerns of conventional right ventricular pacing and the risk of heart failure in a subset of patients.     

Out-of-hospital automatic cardioversion of ventricular tachycardia

A 42 year old man who survived sudden cardiac death was treated with an automatic implantable cardioverter/defibrillator. After a 5 month symptom-free interval, the patient received two internal discharges in the conscious state while wearing an ambulatory electrocardiographic recorder. Analysis of the tape revealed that both discharges were activated by two bursts of polymorphous ventricular tachycardia, the first one occurring at the end and the second at the onset of episodes of slow, hemodynamically stable monomorphous ventricular tachycardia. This case illustrates the reliability of the automatic implantable cardioverter/defibrillator as an antiventricular tachycardia device and the problem posed by its exposure to nonsustained ventricular tachycardia.     

Percutaneous Extraction of Transvenous Defibrillator Leads Using the VascoExtor Pacing Lead Removal System

In the implantable cardioverter defibrillator era the necessity for lead removal is not negligible. A specially designed extraction lead system for percutaneous removal of such leads is lacking, in contrast to the existing pacing lead extraction systems. We report the successful percutaneous extraction of four implantable cardioverter defibrillator leads in three patients because of lead malfunction using a novel pacemaker lead extraction system, the VascoExtor (VascoMed) system. Three leads were successfully removed in two patients using traction with special locking stylets from the superior approach. One lead was removed using the system's additional extraction tools through the femoral approach. There were no complications. This preliminary experience shows that the VascoExtor (VascoMed) pacemaker lead extraction system can also be used in implantable cardioverter defibrillator lead extraction safely and effectively. In addition to the locking stylets, adjunct percutaneous extraction tools may be needed in some cases.     

How to avoid inappropriate therapy

PURPOSE OF REVIEW: With wider indications for implantable cardioverter defibrillator therapy, more patients at lower risk for ventricular tachyarrhythmia receive this treatment. To maintain the ratio of benefit versus side-effects at an acceptable level, the risk of inappropriate implantable cardioverter defibrillator therapy has to be minimized. RECENT FINDINGS: Implantable cardioverter defibrillators require the activation of enhanced detection criteria. These can avoid inappropriate therapy of sinus tachycardia (gradual onset) and atrial fibrillation (irregular rate) while other regular supraventricular tachycardias may be misclassified even with combinations of criteria (QRS morphology, abrupt onset, regular rate). Carefully programmed, dual-chamber implantable cardioverter defibrillators provide better ventricular tachyarrhythmia/supraventricular tachycardias discrimination. Key issues are long tachycardia detection (18 cycles or more), deactivation or restrictive programming of safety therapy despite supraventricular tachycardia classification, and restriction of shock therapy to high tachycardia rates (>or=250 bpm). Further developments are necessary to reduce the incidence of inappropriate therapy due to lead failure that is more frequent in physically active patients. SUMMARY: With optimized programming, the rate of inappropriate ventricular tachyarrhythmia detection is significantly reduced. Particularly the prevention of inappropriate shocks has important implication for the quality of life and acceptance of implantable cardioverter defibrillator treatment.     

Potential device interaction of a dual chamber implantable cardioverter defibrillator in a patient with continuous spinal cord stimulation.

Spinal cord or thalamic deep brain stimulation with a pacemaker is becoming more important in the treatment of drug refractory pain due to peripheral vascular disease, angina pectoris and intractable tremor in patients with neurologic disorders such as Parkinson's disease. An additional indication for a cardiac pacemaker or implantable cardioverter defibrillator raises concerns about possible interactions between the implanted electrical devices. We report on a patient with existing spinal cord stimulation who survived sudden cardiac death and received a dual chamber cardioverter defibrillator capable of delivering tiered therapies in both the atrium and ventricle.     

Audible implantable cardioverter defibrillator alarms detect intermittent conductor discontinuity

The lead conductor integrity of implantable cardioverter defibrillator devices is inferred from impedance measurements; however, intermittent discontinuity can be difficult to detect or confirm. Newer devices can perform daily lead impedance self-testing, and some even have audible alarms that promptly warn patients of anomalies. In the present case, the audible alarms were solely responsible for the timely identification of an intermittent, otherwise clinically nonreproducible, form of potentially fatal implantable cardioverter defibrillator system failure.     

"Add-on pacing lead": An effective and safe alternative to lead replacement in ICD pacing failure

Despite recent advances in implantable cardioverter defibrillator (ICD) technology, the long-term reliability of ICD leads remains a significant problem. Lead failures constitute a major risk for patients with an implantable cardioverter defibrillator. There is no clear consensus on treatment strategy of ICD lead failure and decision should be individualized. We report a pacing-dependent elderly male with ICD lead pacing failure secondary to insulation break resulting in recurrent syncope. We emphasize the technique of "Add-on pacing lead implantation" could be an effective and alternative to ICD lead replacement.     

A novel use of cardiac resynchronization therapy‐defibrillator device in hypertrophic cardiomyopathy

Dual‐chamber implantable cardioverter‐defibrillator is generally used in patients with atrioventricular block and hypertrophic cardiomyopathy with preserved left ventricular ejection fraction. In the current case, a cardiac resynchronization therapy‐defibrillator device was implanted in a patient with non‐obstructive hypertrophic cardiomyopathy with preserved ejection fraction and atrioventricular block to achieve both more physiological pacing and life‐threatening ventricular arrhythmia management.     

Near Fatal Ventricular Fibrillation in Brugada Syndrome Despite Presence of an Implanted Implantable Cardioverter Defibrillator

A 38-year-old man with Brugada syndrome and aborted cardiac arrest was treated with quinidine only, based on the results of electrophysiologic drug testing. Six months later, after suffering a vaso-vagal syncope, he opted to receive an implantable cardioverter defibrillator and decided to discontinue quinidine against our recommendation. Sixty-seven months later, he had recurrent ventricular fibrillation that was terminated only by the sixth maximal energy shock delivered by the device (which has the capability to deliver a maximum of 8 shocks). This case suggests the possible risk in only relying on an implantable cardioverter defibrillator in the management of cardiac arrest survivors with Brugada syndrome.     

Implantable cardioverter defibrillator: charge saver, not syncope saver!

In patients with an implantable cardioverter defibrillator, empirical antitachycardia pacing/burst pacing (ATP) is associated with a significantly decreased rate of appropriate shocks. The use of ATP as first-line therapy in ventricular tachycardia promotes less pain and better quality of life because the number of shocks is reduced. Additionally, battery longevity is substantially increased with this strategy. Based on this, device manufacturers have developed new algorithms to optimize the use of ATP and shocks in patients with an implantable cardioverter defibrillator. The present report describes a case in which the use of one of these new algorithms was associated with a significant delay in tachycardia termination and, consequently, led to syncope.     

Assessment of cardiac sympathetic activity by MIBG imaging in patients with heart failure: a clinical appraisal

Cardiac sympathetic activity can be assessed by (123)I-labelled meta-iodobenzylguanidine (MIBG) scintigraphy. Abnormalities of sympathetic cardiac activity have been shown in patients with heart failure, resulting in reduced MIBG uptake. Abnormal MIBG uptake predicts cardiac death, arrhythmias and all-cause mortality in patients with heart failure with a prognostic power incremental to that of conventional risk markers, and may identify patients at low risk of arrhythmias despite current guideline indications for implantable cardioverter defibrillator or patients at high risk for arrhythmias not fulfilling implantable cardioverter defibrillator indications. Prospective outcome studies are needed to assess whether MIBG imaging will have an impact on the mortality and morbidity of patients with heart failure.     

Adverse interaction between a left ventricular assist device and an implantable cardioverter defibrillator

An increasing number of patients have a coexisting implantable cardioverter defibrillator (ICD) and left ventricular assist device (LVAD) to treat ventricular arrhythmias and refractory heart failure, respectively. To date, there have been no published reports of negative interactions between these devices that have impacted appropriate ICD or LVAD function. In this case report, we describe a patient with an LVAD-ICD interaction that necessitated replacement of the implantable defibrillator.     

Routine implantation of cardioverter/defibrillator devices in patients aged 75 years and older with prior myocardial infarction and left ventricular ejection fraction < 30: antagonist viewpoint

The Multicenter Automatic Defibrillator Implantation Trial (MADIT II) investigators assert that their results justify the placement of artificial implantable defibrillator cardioverter devices in patients aged 75 years and older with prior myocardial infarction and left ventricular dysfunction (ejection fraction of 30 or less). The authors claim that the results of the trial do not justify this conclusion. The majority of patients were male (84%) and aged 64±10 years. Also, 2.8% of patients assigned to the defibrillator group and 1.5% had their device removed. Of the latter subgroup, nine patients (1.3%) received a heart transplant. Twelve had their artificial implantable defibrillator cardioverter device deactivated mostly because of terminal illness. Although the study results show a significant reduction in mortality over the control group (absolute reduction=5.6%), almost the same percentage required hospitalization because of manifestation of congestive heart failure (absolute value 5%; p= 0.09). Also, 1.8% had lead problems, 0.7% had infections, and the benefits were only seen after the first year. Caution is needed before the results of this study are applied to a much older cohort comprised mainly of women in whom heart transplant is contraindicated and who have multiple health problems, including cognitive impairment. Artificial implantable cardioverter/defibrillator devices are expensive and this study's results need to be duplicated in other comparable cohorts.     

Comparison of effectiveness of implantable cardioverter defibrillator in patients with idiopathic dilated cardiomyopathy versus those with proved coronary heart disease

This study analyzes the effectiveness of the implantable cardioverter defibrillator in a group of 40 consecutive patients with idiopathic dilated cardiomyopathy and sustained ventricular arrhythmia; these patients were compared with a control group of 80 consecutive patients with proved coronary artery disease. There were no differences in the type and probability of recurrences at follow-up. Most recurrences were due to sustained monomorphic ventricular tachycardia, and the efficacy of the defibrillator in treating the arrhythmia was the same in both groups.