Implantable cardioverter defibrillator: use in patients with no symptoms and at high risk

Prophylactic defibrillator implantation in patients with nonischemic dilated cardiomyopathy

BACKGROUND

Patients with nonischemic dilated cardiomyopathy are at substantial risk for sudden death from cardiac causes. However, the value of prophylactic implantation of an implantable cardioverter-defibrillator (ICD) to prevent sudden death in such patients is unknown.

METHODS

We enrolled 458 patients with nonischemic dilated cardiomyopathy, a left ventricular ejection fraction of less than 36 percent, and premature ventricular complexes or nonsustained ventricular tachycardia. A total of 229 patients were randomly assigned to receive standard medical therapy, and 229 to receive standard medical therapy plus a single-chamber ICD.

RESULTS

Patients were followed for a mean (+/-SD) of 29.0+/-14.4 months. The mean left ventricular ejection fraction was 21 percent. The vast majority of patients were treated with angiotensin-converting-enzyme (ACE) inhibitors (86 percent) and beta-blockers (85 percent). There were 68 deaths: 28 in the ICD group, as compared with 40 in the standard-therapy group (hazard ratio, 0.65; 95 percent confidence interval, 0.40 to 1.06; P=0.08). The mortality rate at two years was 14.1 percent in the standard-therapy group (annual mortality rate, 7 percent) and 7.9 percent in the ICD group. There were 17 sudden deaths from arrhythmia: 3 in the ICD group, as compared with 14 in the standard-therapy group (hazard ratio, 0.20; 95 percent confidence interval, 0.06 to 0.71; P=0.006).

CONCLUSIONS

In patients with severe, nonischemic dilated cardiomyopathy who were treated with ACE inhibitors and beta-blockers, the implantation of a cardioverter-defibrillator significantly reduced the risk of sudden death from arrhythmia and was associated with a nonsignificant reduction in the risk of death from any cause.

Implantable defibrillator event rates in patients with idiopathic dilated cardiomyopathy, nonsustained ventricular tachycardia on Holter and a left ventricular ejection fraction below 30%

OBJECTIVES

This study investigated the incidence of appropriate implantable cardioverter defibrillator (ICD) interventions for ventricular tachycardia (VT) or ventricular fibrillation (VF) in patients with idiopathic dilated cardiomyopathy (IDC) and nonsustained VT in the presence of a left ventricular ejection fraction below 30%, versus in patients with syncope and patients with a history of VT or VF.

BACKGROUND

To date, only limited information is available about the prophylactic use of ICDs in patients with IDC.

METHODS

From January 1993 to July 2000, 101 patients with IDC underwent implantation of ICDs with electrogram storage capability at our institution. Patients were placed into one of three groups according to their clinical presentation: asymptomatic or mildly symptomatic nonsustained VT in the presence of a left ventricular ejection fraction < or = 30% (49 patients, prophylactic group), unexplained syncope or near syncope (26 patients, syncope group) and a history of sustained VT or VF (26 patients, VT/VF group).

RESULTS

During 36 +/- 22 months follow-up, 18 of 49 patients (37%) in the prophylactic group received appropriate shocks for VT or VF, compared with 8 of 26 patients (31%) in the syncope group and with 9 of 26 patients (35%) of the VT/VF group. Multivariate Cox analysis of baseline clinical variables identified left ventricular ejection fraction, atrial fibrillation and a history of sustained VT or VF as predictors for appropriate ICD interventions during follow-up.

CONCLUSIONS

Patients with IDC and prophylactic ICD implantation for nonsustained VT in the presence of a left ventricular ejection fraction < or = 30% had an incidence of appropriate ICD interventions similar to that of patients with a history of syncope or sustained VT or VF. These findings indicate that ICDs may have a role in not only secondary but also primary prevention of sudden death in IDC.

Therapeutic developments in sudden cardiac death

Sudden cardiac death is characterised by the unexpected death of a patient who has been clinically stable. It is frequently due to the development of ventricular tachyarrhythmias. With appropriate treatment, patients can be appropriately resuscitated. Clinically, it is essential to develop treatment strategies to prevent such an episode, as most patients do not survive out-of-hospital cardiac arrest. beta-Blockers are an effective pharmacological therapy in patients following myocardial infarction and in those with congestive heart failure. They may also be effective in other types of heart disease. Anti-arrhythmic agents are not useful as prophylactic drug therapy for reducing mortality in patients at risk for sudden cardiac death. Amiodarone is a notable exception, which may have some benefit, particularly in some subgroups. The implantable cardioverter-defibrillator has emerged as the most effective therapy for preventing sudden cardiac death in high-risk patients. Further work is required to enhance the characterisation of high-risk patients. Genetic analyses in patients with cardiovascular disorders may also identify new approaches to the prevention of sudden cardiac death.

Defibrillators in nonischemic cardiomyopathy treatment evaluation

The Defibrillators in Nonischemic Cardiomyopathy Treatment Evaluation (DEFINITE) is a multicenter randomized trial. Patients will have nonischemic cardiomyopathy (LVEF < or = 35%), a history of symptomatic heart failure and spontaneous arrhythmia (> 10 PVCs/hour or nonsustained ventricular tachycardia defined as 3-15 beats at a rate of > 120 beats/min) on Holter monitor or telemetry within the past 6 months. Patients will be randomized to an implantable cardioverter defibrillator (ICD) versus no ICD. All patients will receive standard oral medical therapy for heart failure including angiotensin converting enzyme inhibitors and beta-blockers (if tolerated). Patients will be followed for 2-3 years. The primary endpoint will be total mortality. Quality-of-life and pharmacoeconomics analyses will also be performed. A registry will track patients who meet basic inclusion criteria but are not randomized. We estimate an annual total mortality of 15% at 2 years in the treatment arm that does not receive an ICD. The ICD is expected to reduce mortality by 50%. Approximately 204 patients will be required in each treatment group. Twenty-five centers will be included in a trial designed to last an estimated 4 years.

Health-related quality-of-life assessment of patients with life-threatening ventricular arrhythmias

The purpose of this study was to determine whether treatments for life-threatening ventricular arrhythmias are associated with quality-of-life (QOL) and psychological distress. Multidimensional measures of QOL and psychological distress were used to cross-sectionally compare patients with ICDs to patients treated with antiarrhythmic drugs and patients without serious cardiac conditions. The sample consisted of 157 patients: 35 patients treated with antiarrhythmic medication only, 24 patients treated with ICD only, 25 patients treated with ICD and antiarrhythmic medication, and 73 controls. Patients completed the Medical Outcomes Study SF-36 health survey, the Brief Symptom Inventory, and background questionnaires. There were no significant differences in self-reported QOL and psychological distress between patients with or without ICD, and the occurrence of defibrillator shocks was unrelated to QOL and psychological distress. However, patients treated with antiarrhythmic drugs reported greater QOL impairment in physical functioning, vitality, emotional role limitations, and sleep, as well as greater psychological distress than patients not treated with antiarrhythmics. These limitations may be attributed to adverse effects arising from antiarrhythmic pharmacotherapy. Results of the present investigation suggest that QOL and psychological distress are maintained among ICD patients, whereas treatment with antiarrhythmic drugs are associated with a diminished QOL and greater psychological distress. These findings may assist cardiologists to select the optimal treatment for life-threatening ventricular arrhythmias that minimizes disturbances in health-related QOL and psychological distress and increases patient compliance.

Familial dilated cardiomyopathy and spontaneous ventricular arrhythmias

Two members of a family with (autosomal dominant) dilated cardiomyopathy and symptomatic short-lasting ventricular tachyarrhythmias were each treated with an ICD in the course of their disease. One patient had an episode of torsades de pointes induced by amiodarone, and the ICD failed to recognize some events. Cardiac arrest recurred in this setting. Treatment with bisoprolol was helpful in maintaining an acceptable functional status and in preventing multiple shocks until transplantation became mandatory. Bisoprolol was not tolerated by the second patient, who had several episodes of syncope because of nonsustained ventricular tachycardia. His functional course went downhill fast, and he received a heart transplantation 16 months after implantation of an ICD, which had not delivered any shocks, in spite of one symptomatic short ventricular tachycardia.