Empiric amiodarone versus "ineffective" drug therapy in patients with refractory ventricular tachyarrhythmias

Ventricular arrhythmias, electrophysiologic studies, and devices

Because of the high incidence of heart disease in the elderly, ventricular tachyarrhythmias are not infrequent. Determining the nature and extent of the underlying heart disease and identifying precipitating causes is required prior to instituting long-term therapy. Recent studies suggest that for hemodynamically unstable ventricular tachyarrhythmias, mortality is lower with the implantable cardioverter-defibrillator compared with pharmacologic therapy. This benefit is likely to be more modest in the elderly because of competing cardiac and noncardiac causes of death. For similar reasons, the favorable results reported with the prophylactic use of the implantable cardioverter-defibrillator are likely to be attenuated in the elderly.

The value of oral amiodarone in the treatment of ventricular arrhythmias in heart disease

The antiarrhythmic properties of amiodarone at the ventricular level were discovered in the early 1970s. The unanimously recognised efficacy of amiodarone includes a weak negative inotropic effect and compensatory vasodilatory properties, making amiodarone particularly suitable for treating the potentially malignant arrhythmias associated with organic disease. In a review of 611 hospitalised patients on amiodarone, and 353 patients in whom the drug had been prescribed, over a 52-month period in our 60-bed department, we noted that amiodarone was prescribed in 53% of patients for arrhythmias and in 47% of patients for coronary insufficiency. Ventricular arrhythmias represented 13% of the rhythmic indications. These indications differ from those in the USA. The efficacy (70 to 90%) of amiodarone in ventricular extrasystoles has been shown in open studies. In coronary patients, the antiarrhythmic activity of amiodarone is superior to that of propranolol. However, there has been no controlled study because the need for a loading dosage, and the electrocardiographic effects render such studies difficult. After myocardial infarction, ventricular arrhythmias constitute a significant risk factor independently of prognosis; amiodarone may be useful in this indication, and studies of the European Myocardial Infarction Amiodarone Trial (EMIAT) type will examine its value here. Since 1973, it has been recognised that amiodarone can prevent ventricular tachycardia in 55 to 89% of patients in the clinical situation. After a long-standing controversy, the positive predictive value of programmed stimulation has finally been agreed on. In hypertrophic cardiomyopathy, retrospective studies suggest a reduction in mortality in patients treated with amiodarone. By contrast, the value of amiodarone in dilated cardiomyopathy requires more intensive investigation. We consider amiodarone to be indicated in ventricular arrhythmic complexes, particularly if they are associated with an ejection fraction of less than 35% and/or atrial fibrillation. The value of amiodarone in arrhythmias associated with heart failure needs to be evaluated. In conclusion, amiodarone is a powerful antiarrhythmic agent but, because of the possibility of dose- and duration-dependent side effects, evaluation of the risk: benefit ratio in each indication is needed.

Actuarial incidence and pattern of occurrence of shocks following implantation of the automatic implantable cardioverter defibrillator

The actuarial incidence and pattern of occurrence of shocks were analyzed in 65 patients after implantation of the automatic implantable cardioverter defibrillator. During a mean follow-up of 25 +/- 21 months only one patient died suddenly, and this patient had a nonfunctioning device at the time of death. The long-term actuarial risk of death from any cause in the patients who received appropriate shocks was not significantly different than for the entire group. The 1- and 4-year cumulative risk of receiving any shock was 51 +/- 7% and 81 +/- 11%; of receiving an appropriate shock was 33 +/- 7% and 64 +/- 10%; of receiving a spurious shock was 17 +/- 5% and 21 +/- 6%; and of receiving an "indeterminate" shock was 19 +/- 6% and 52 +/- 10%. In 14 patients who were followed for 24 months without receiving an appropriate shock, the actuarial risk of receiving an appropriate shock was 29 +/- 14% during the next 24 months. The mean number of shocks delivered during appropriate episodes was 1.6 +/- 0.9, which was significantly lower than the mean of 4.0 +/- 2.0 shocks during spurious episodes (P less than 0.02). The mean number of shocks during indeterminate episodes was 1.7 +/- 1.5. Our data confirms the efficacy of the implantable defibrillator in preventing sudden death. The majority of patients with this device receive appropriate shocks during long-term follow-up, and the cumulative incidence of appropriate shocks increases steadily for at least 4 years. In contrast, the cumulative incidence of spurious shocks plateaus at about 12 months. Our data suggests that many "indeterminate" shocks actually appear to be appropriate.