Inpatient versus outpatient initiation of antiarrhythmic drug therapy for patients with supraventricular tachycardia.

In-hospital initiation of antiarrhythmic drug therapy is often recommended to observe the effects of the drug and monitor for possible adverse reactions, especially proarrhythmia. However, the actual risk of proarrhythmia in patients undergoing treatment for supraventricular tachyarrhythmias is not well defined. While patients with ventricular tachycardia or ventricular fibrillation most often have underlying structural heart disease, this is not true for many patients with supraventricular tachycardia. It is therefore necessary to define more precisely which patients with supraventricular tachycardia are at risk for ventricular proarrhythmia and sudden cardiac death. An indepth analysis was conducted of 162 patients from 51 published reports of ventricular proarrhythmic events in patients treated for supraventricular tachycardia. Heart disease of various etiologies was present in 96% of patients. Proarrhythmia occurred most commonly with quinidine (72% of cases), and torsade de pointes was the most frequently proarrhythmic event (54%). More than half of all proarrhythmic events occurred within the first 3 days of initiating therapy or soon after increasing the dose of chronic drug therapy. Information was scant regarding the time to occurrence of ventricular proarrhythmia with flecainide and propafenone. With flecainide, nine cases were reported at varying times after initiation of therapy, from in-hospital to 8 months. Two cases of proarrhythmia with propafenone occurred at Day 10 and at 2 years. Because of the low frequency of proarrhythmia, in-hospital initiation of antiarrhythmic drug therapy may not be cost-effective. It is recommended when the effects of the drugs on the arrhythmia must be monitored, or when initiating treatment or increasing the drug dose in patients with structural hear disease.(ABSTRACT TRUNCATED AT 250 WORDS)