Single-chamber versus dual-chamber implantable cardioverter defibrillators: indications and clinical results

Inappropriate ICD Therapy: Does Device Configuration Make a Difference

INTRODUCTION

Inappropriate implantable cardioverter defibrillator (ICD) therapy (IT) is a common complication in patients with ICD. IT is commonly triggered by supraventricular tachycardias (SVT). Dual chamber ICDs (D-ICDs) may distinguish SVT from ventricular tachycardia/ventricular fibrillation better than single chamber ICDs (S-ICDs) and may be associated with a smaller incidence of IT.

METHODS

We reviewed the charts of 386 patients who had an ICD implanted for an AHA class I indication. Intracardiac electrograms were used to classify shocks as either appropriate or inappropriate.

RESULTS

Of 295 patients with an S-ICD, 66 (22.3%) received IT, compared to 5 (5.4%) of 91 patients with a D-ICD. The likelihood of being event-free at 1, 2, 3, and 4 years was 96.1%, 96.1%, 96.1%, and 89% for patients with D-ICD and 80.7%, 72.7%, 69.6%, and 66.4%, respectively, for patients with S-ICD (P < 0.001). Multivariate analysis showed no significant association with age, sex, history of atrial fibrillation, history of hypertension, or ejection fraction. SVTs were the commonest cause of IT in our patients.

CONCLUSION

Patients with D-ICD are less likely to receive IT as compared to patients with S-ICD.

The use of implantable cardioverter defibrillators in Iceland: a retrospective population based study

Background

Indications for implantable cardioverter defibrillator (ICD) implantation have expanded considerably in recent years, resulting in steadily growing numbers of ICD recipients worldwide. The aim of this study was to review the overall experience with ICDs in Iceland.

Methods

This was a retrospective single centre study set at the University Hospital in Iceland. Data on all ICD implantations in Iceland from the first implantation in 1992 till the end of 2002 was reviewed.

Results

Sixty-two patients (71% male) received an ICD during this period. There was an increase in the number of implants by year and the number of new implants in 2001 and 2002 amounted to 56 and 38 per million, respectively. The mean age at implantation was 58 (+/-14) years. Forty patients (65%) had coronary artery disease. The most common indications for ICD implantation were cardiac arrest, 32 (52%) and another 26 (42%) had experienced ventricular tachycardia without cardiac arrest. The most common adverse event was inappropriate shocks. Twenty-eight patients (45%) received therapy from their ICDs, with the majority receiving appropriate therapy. Of the thirteen patients deceased before or during the study period, no case of sudden arrhythmic death was observed.

Conclusion

This study shows that the experience with ICDs in Iceland is in most respects similar to other Western countries.

Differences in outcomes between patients treated with single- versus dual-chamber implantable cardioverter defibrillators: a substudy of the Multicenter Automatic Defibrillator Implantation Trial II

OBJECTIVES

We sought to evaluate the influence of single- versus dual-chamber implantable cardioverter defibrillators (ICDs) on the occurrence of heart failure and mortality as well as appropriate and inappropriate ICD therapy in the Multicenter Automatic Defibrillator Implantation Trial II (MADIT-II).

BACKGROUND

In MADIT-II, ICD therapy in patients with a prior myocardial infarction and ejection fraction < or =0.30 was associated with a 31% reduction in risk of mortality when compared to conventionally treated patients. An unexpected finding was an increased occurrence of hospitalization for heart failure in the ICD group.

METHODS

Data from 717 patients randomized to ICD therapy with single- or dual-chamber pacing devices in MADIT-II were retrospectively analyzed. Endpoints selected for analysis included death from any cause, new or worsening heart failure requiring hospitalization, death or heart failure, appropriate therapy for ventricular tachycardia (VT) or ventricular fibrillation (VF), and inappropriate ICD therapy for atrial fibrillation or supraventricular tachycardia.

RESULTS

A total of 404 single-chamber ICDs (S-ICDs) and 313 dual-chamber ICDs (D-ICDs) were implanted. Patients receiving D-ICDs were at a higher risk at baseline than those receiving S-ICDs, with older age, higher NYHA class, more frequent prior CABG, wider QRS complex, more LBBB, higher BUN level, a history of more atrial arrhythmias requiring treatment, and a longer time interval from their index myocardial infarction to enrollment. While there was a trend toward an increase in adverse outcomes in the D-ICD group, no statistically significant differences in heart failure or mortality were observed between S-ICD versus D-ICD groups.

CONCLUSIONS

Patients with D-ICDs had a nonsignificant trend toward higher mortality and heart failure rates than patients with S-ICDs.

Should all implantable cardioverter defibrillators for ventricular arrhythmias be dual-chamber devices?

The advantages of a dual-chamber implantable cardioverter defibrillator (ICD) over a single-chamber ICD include physiologic pacing capability, atrial electrogram storage, enhanced arrhythmia discrimination algorithms, and a potential to treat atrial arrhythmia by pacing or defibrillation. Current evidence supports the supposition that dual-chamber ICDs are definitely indicated in patients who have a concomitant indication for physiologic pacing, such as bradycardia or bradycardia-dependent ventricular tachyarrhythmias. Refined dual-chamber arrhythmia discrimination algorithms and enhanced atrial therapies are probably required for patients with frequent supraventricular arrhythmias. Furthermore, in patients with systolic heart failure, low ejection fraction, and intraventricular conduction delay, triple-chamber ICDs with biventricular pacing may improve their functional status and prevent sudden arrhythmic death. Careful patient selection is required to optimize the cost-effectiveness of these sophisticated technologies.

Current status of the implantable cardioverter-defibrillator

Clinical trials have established the superiority of the implantable cardioverter-defibrillator (ICD) over antiarrhythmic drug therapy in survivors of sudden cardiac death and in high-risk patients with coronary artery disease. The ICD has evolved to overcome the limitation of earlier devices that required thoracotomy for implantation and were fraught with inappropriate shock delivery. Current ICDs are implanted in a similar manner to cardiac pacemakers and incorporate sophisticated rhythm-discrimination algorithms to prevent inappropriate therapy. Managing the patient with an ICD requires an understanding of the multiprogrammable features of modern devices. Drug interactions and potential sources of electromagnetic interference may adversely affect ICD function. Driving restrictions may be necessary under certain conditions. The cost-effectiveness of ICD therapy appears favorable, given the marked survival benefit seen in randomized trials relative to antiarrhythmic drug treatment. The growing number of ICD recipients necessitates an understanding of the specialized features of the modern ICD and the role of device therapy in clinical practice.

Implantable dual-chamber cardioverter-defibrillator-pacemaker

The fifth generation of implantable cardioverter-defibrillators offer enhanced modes of detection of atrial and ventricular arrhythmias, antitachycardia pacing and shocks, multiprogrammability, intracardiac electrogram storage, and all functions of antibradycardia dual-chamber pacing including rate responsiveness and mode switching. There is no consensus on the indications for dual-chamber pacemaker defibrillator systems. This review focuses on the four major options of newer devices that might benefit patients: 1) permanent dual-chamber pacing in ischemic coronary disease patients, 2) detection and management of atrial fibrillation or other atrial tachyarrhythmias, 3) some newer indications for pacing, and 4) the suppression of inappropriate interventions. On the basis of published data, newer indications for the dual-chamber systems, advantages and limitations, and future perspectives are discussed.

Drug therapy of sustained ventricular tachyarrhythmias. Is there still a role?

This article provides a review of the risks faced by patients with sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) in the absence of a reversible or transient cause so that the goals of therapy can be clearly defined. The therapeutic approaches that have been proposed to achieve these goals are outlined and evidence comparing these various approaches to therapy is then summarized in order to propose an algorithm for the optimal use of antiarrhythmic drug therapies as primary therapy for selected VT/VF patients. Options for the ancillary uses of antiarrhythmic drug therapies in ICD patients are considered.