Thursday, February 23, 2006

Internal Cardioverter Defibrillator (ICD) and Antiarrhythmic Drug Interaction

Internal Cardioverter Defibrillator (ICD) and Antiarrhythmic Drug Interaction

Steven Singh, M.D.

ICDs were developed and have been most frequently used for prevention of sudden cardiac death in patients with life-threatening ventricular arrhythmias such as sustained VT or VF. Epidemiological studies report high rates of recurrence of these life-threatening arrhythmias (30% to 50% in 2 years) during follow-up. Early observational reports documenting efficacy in reversion of sustained VT and VF have now been supplemented by large prospective and sometimes randomized single-center and multicenter studies with long-term outcome data. Enrollment in these trials has included patients with coronary and noncoronary heart diseases with a wide range of ventricular function and coexisting disorders.

These studies uniformly document sudden cardiac death recurrence rates that average 1% to 2% annually after device implantation in these populations. Simultaneously, rapid technological evolution of ICD systems has occurred. The ICD has evolved from a short-lived nonprogrammable device requiring a thoracotomy for lead insertion into a multiprogrammable antiarrhythmia device inserted almost exclusively without thoracotomy, now capable of treating bradycardia, VT, and VF. Clinical studies have recorded major improvements in implant risk, system longevity, symptoms associated with arrhythmia recurrences, quality of life and diagnosis and management of inappropriate device therapy. Implantation, follow-up and replacement of these devices is a complex process requiring familiarity with device capabilities, adequate case volume, continuing education and skill in the management of ventricular arrhythmias, therefore mandating involvement of a trained electrophysiologist to provide an optimal personnel team for patient safety and device management. A substantial new body of information has emerged regarding the clinical outcome of patients with VT or VF treated with currently available antiarrhythmic therapies. There are currently three major therapeutic options to reduce or prevent VT or VF in patients at risk for these arrhythmias. These are:

  1. Antiarrhythmic drug therapy selected by electrophysiological study or ambulatory monitoring or prescribed empirically.
  2. Ablative techniques applied at cardiac surgery or percutaneously using catheter techniques.
  3. Implantation of a cardioverter-defibrillator device system.

A combination of ICD therapy with drugs or ablation is also frequently used. Currently the largest clinical experience is with combined antiarrhythmic drug and ICD therapy. The role of antiarrhythmic drugs combined with an ICD has not been thoroughly evaluated, though several clinical trials have been conducted. The results of these studies raise a number of important clinical issues in patients with life-threatening ventricular arrhythmias. Antiarrhythmic therapy, with the possible exception of sotalol, should be prescribed selectively in patients with ICDs, given their potential for cardiac and noncardiac toxicity.


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