A Low Incidence of Proarrhythmia Using Low-Dose Amiodarone (original) (raw)
1988, Journal of Electrophysiology
KERIN NZ, ET AL: LOW incidence of proarrhythmia using low-dose amiodarone. The incidence of proarrhythmia with antiarrhythmic agents is reported to be 2%-23%, depending on the agent, definition of proarrhythmia, method of assessment, and severity of underlying rhythm disturbance. Several case reports of amiodarone-induced proarrhythmia have appeared; however, its prevalence and clinical significance have not been adequately defined. In our series of 107 patients with potentially lethal ventricular arrhythmias, amiodarone was administered as a 5-mg/kg bolus infusion, followed by 600-800 mg/day for 7-10 days. A mean daily maintenance dose of 270 mg/day was given for an average of 15 months (range <57). Proarrhythmia was defined by the method ofMorganroth as: (1) a three-to tenfold increase in VPC frequency, (2) a marked increase in VT rate, or (3) the development of new sustained VT/VF or torsade de pointes. Bradyarrhythmias, conduction delays, and out-of-hospital sudden death were not included by definition. Baseline 24-hour-Holter monitoring revealed 449 ± 685 VPCs/hr, 740 ± 584 couplets/24 hr, and 61 + 685 episodes of nonsustained VT/24 hr. Proarrhythmia occurred in three patients (2.8%). Two of these episodes occurred during the first week of treatment and resolved without dosage adjustment. These episodes included a 4.7-and 5.1-fold increase in VPC frequency. The other proarrhythmic event was a case of torsade de pointes that occurred after 12 months of treatment and required acute intervention and withdrawal of amiodarone. In conclusion, lowdose amiodarone appears to have a low potential for proarrhythmia and compares favorably with other agents in this regard, perhaps owing to its unique electrophysioiogic properties.
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The determinants of long-term clinical outcome were studied in 42 patients with recurrent ventricular tachycardia (VT) or ventricular fibrillation (VF) who were treated with amiodarone as the sole antiarrhythmic agent. Of the 42 patients, 11 (26 % ) either died suddenly or had recurrent, symptomatic, sustained VT during a mean follow-up period of 10 months (range 0.3 to 45). Of the 19 patients without inducible VTNF during electrophysiologic study while receiving amiodarone, 1 patient died suddenly but no patient had recurrent VTNF. Ten of the 23 patients (43 % ) with persistently inducible arrhythmia have died suddenly or have had recurrent VTNF. Using survival and stepwise logistic re-gression analyses, 2 significant independent predictors of recurrent arrhythmia were identified; persistently inducible VT during electrophysiologic testing in patients receiving amiodarone therapy (p <0.002) and the left ventricular ejection fraction at rest (p <0.05). The predictive accuracy of the response to serial electrophysiologic testing during amiodarone therapy was 67 %, the sensitivity was 56% and the specificity was 91%. Thus, serial electrophysiologic testing is useful for determining the prognosis in patients with inducible VTNF treated with amiodarone.
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