Combining antiarrhythmic drugs and implantable devices therapy: benefits and outcome

Aggravation of Arrhythmia by Antiarrhythmic Drugs (Proarrhythmia)

Arrhythmia aggravation by antiarrhythmic drugs (proarrhythmia) can be caused by worsening or a change of a preexisting arrhythmia, development of a new arrhythmia, or development of a bradyarrhythmia. Aggravation of arrhythmia usually occurs within several days of beginning an antiarrhythmic drug or increasing the dose of the drug. The time of occurrence is based on the particular drug and its pharmacokinetic properties. Although there are no ways to predict the patient at risk for developing arrhythmia aggravation with any specific agents, risk factors include QT interval prolongation, elevated serum levels of the drug, electrolyte abnormalities, presence of heart failure, a history of a sustained ventricular tachyarrhythmia, and underlying myocardial ischemia.

Hybrid therapies for ventricular arrhythmias

In recent years several trials demonstrated the efficacy of implantable cardioverter-defibrillation (ICD) therapy in reducing cardiac and total mortality in patients affected by rapid ventricular tachycardia (VT) and/or ventricular fibrillation. Nevertheless, ICD do not prevent arrhythmia recurrences, thus being a palliative and not a curative treatment modality. The tolerance to ICD therapy varies greatly, and within individuals, this leading to a nonuniform acceptance of this form of therapy. The very frequent occurrence of VT, defined as an arrhythmic storm, may be a life threatening condition. The majority of ICD patients is under antiarrhythmic drug therapy, to reduce episodes of VT or to make antitachycardia pacing more effective by slowing the tachycardia rate. Drug therapy, however, may cause additional problems, and does not represent the optimal solution. The prevention of VT and/or ventricular fibrillation episodes and excessive ICD therapy, remains a worthwhile goal. Radiofrequency catheter ablation (RFCA) is a curative approach, and can be expected to reduce the frequency of recurrent VT episodes in the majority of patients. The combination of these treatment modalities (ICD and RFCA) is often described as hybrid therapy, implying that the two treatments act providing some form of synergism. In experienced centers, RFCA is now performed, regardless of whether the VT rate is rapid and/or is hemodynamically unstable. Newer mapping and ablation techniques are now available, enhancing the acute success rate of the procedure. In this review the most recent application of VT catheter ablation and the use of advanced mapping and ablation techniques will be discussed.

Is there a role for antiarrhythmic drugs in patients with implantable defibrillators?

With remarkable advancement in technology and clinical research, implantable cardioverter defibrillators (ICDs) have replaced antiarrhythmic drugs as the preferred modality for both primary and secondary prevention of arrhythmic deaths. However, concomitant use of antiarrhythmics in patients with ICDs remains common, often for prevention or reduction of appropriate and inappropriate shocks caused by ventricular and supraventricular arrhythmias, respectively. The role of empiric antiarrhythmic therapy in this patient population remains less clearly defined, with conflicting information from various small randomized trials. Use of antiarrhythmic drugs in the ICD patient population not only can cause potentially serious side effects but can also interact or interfere with the ICD device function. In addition, the effect on survival in patients with ICDs is not well characterized. Given the many potential side effects, drug-device interactions, unclear survival effect, and lack of convincing clinical data supporting its use, empiric antiarrhythmic therapy in the ICD patient population cannot be recommended at this time.

Effect of Concomitant Antiarrhythmic Therapy on Survival in Patients with Implantable Cardioverter Defibrillators

BACKGROUND

Application of implantable cardioverter defibrillator (ICD) therapy is expanding to include both primary and secondary prevention of sudden cardiac death and has been proven to be superior to conventional antiarrhythmic therapies. Concomitant antiarrhythmic drug therapy in patients with ICD is common. These drugs are potentially proarrhythmic, alter defibrillation thresholds, and may affect response to device therapy. However, the impact of concomitant antiarrhythmic drug therapy on survival in patients with ICD devices is unknown.

METHODS

We investigated the effect of different antiarrhythmic drugs on survival when given concomitantly in 360 consecutive ICD patients from our university medical center. Mortality data were obtained from the national death index. Survival analysis was performed using the Kaplan-Meier method. Corrections for significant covariates and group differences were made using the Cox regression model.

RESULTS

Patients were followed up for 4.4 +/- 3.7 years. There were 68 deaths over this period with a 5-year survival of 80%. Patient characteristics were: age 62 +/- 13 years, left ventricular (LV) ejection fraction (EF) 33 +/- 17%, ischemic etiology of LV dysfunction 68%, diabetes mellitus 19%, hypertension 49%, atrial fibrillation 23%, digoxin 43%, beta-blocker 46%, amiodarone 28%, and sotalol 9%. The use of beta-blockers was associated with a better survival (P = 0.0005). This effect persisted after correcting for age, heart rate, EF, and ischemic etiology. The beneficial effect of beta-blocker was unrelated to its effect on heart rate. Digoxin use was associated with a lower survival only on univariate analysis (P = 0.006), but not after adjusting for other variables on a Cox regression model (P = 0.093). Amiodarone and sotalol were found to have a neutral effect on survival.

CONCLUSION

In patients with ICDs, beta-blockers had a favorable effect on survival. Sotalol and amiodarone had a neutral effect on survival. There was a trend toward a deleterious effect with digoxin use. These findings suggest a need for further investigation addressing survival effects of antiarrhythmic drugs when given concomitantly in patients with ICDs.

Azimilide decreases recurrent ventricular tachyarrhythmias in patients with implantable cardioverter defibrillators

OBJECTIVES

This study evaluated the effects of azimilide dihydrochloride (AZ) on anti-tachycardia pacing (ATP) and shock-terminated events in patients with implantable cardioverter defibrillators (ICDs).

BACKGROUND

Animal studies have shown the effectiveness of AZ for therapy of supraventricular and ventricular tachycardia (VT). Azimilide dihydrochloride was investigated as adjunctive treatment for reducing the frequency of VT and, thus, the need for ICD therapies, including ATP and cardioversion/defibrillation (ICD shocks) in patients with inducible monomorphic VT.

METHODS

A total of 172 patients were randomized to daily treatment with placebo, 35 mg, 75 mg, or 125 mg of oral AZ in this dose-ranging pilot study of patients with ICDs. The majority of patients had a history of documented remote myocardial infarction and congestive heart failure New York Heart Association class II or III.

RESULTS

The frequency of appropriate shocks and ATP were significantly decreased among AZ-treated patients compared with placebo patients. The incidence of ICD therapies per patient-year among the placebo group was 36, and it was 10, 12, and 9 among 35 mg, 75 mg, and 125 mg AZ patients, respectively (hazard ratio = 0.31, p = 0.0001). Azimilide dihydrochloride was generally well tolerated and did not affect left ventricular ejection fraction or minimal energy requirements for defibrillation or pacing.

CONCLUSIONS

Azimilide dihydrochloride may be a safe and effective drug for reducing the frequency of VT and ventricular fibrillation in patients with implanted ICDs.

Rationale and patient selection for "hybrid" drug and device therapy in atrial and ventricular arrhythmias

Three quite different forms of direct antiarrhythmic therapy are available for the treatment of cardiac arrhythmias: antiarrhythmic drugs, cardiac ablation and implantable devices (pacemakers and defibrillators). None of these therapies is fully effective and consequently they are increasingly combined. This combination therapy is often described as "hybrid" a term that implies fundamental different qualities of treatment which together provide some form of synergism. The mechanisms for the initiation and perpetuation of most cardiac arrhythmias are complex and multiple. It is therefore not surprising that single therapies are not completely effective. Theoretically the use of multiple different therapies allows more specific mechanisms of arrhythmia to be directly addressed. However, this is largely a theoretical concept that has only been strictly evaluated in a small number of studies. Studies of multiple therapies are difficult to perform unless the combination therapy is regarded as a strategy which can be compared to baseline, conventional treatment or one or more single constituent therapies from the combination. Despite the lack of formal studies there is a very substantial clinical experience which testifies to the value of hybrid therapy for the management of both atrial fibrillation and ventricular tachycardia/fibrillation.