Summary: Intravenous flecainide acetate (2 mg/kg) was administered to 40 patients undergoing routine electrophysiological evaluation for the investigation of recurrent paroxysmal tachycardias. Ten patients had recurrent atrial flutter, 11 patients had recurrent atrial fibrillation, one of whom also had paroxysmal left atrial tachycardia, and 19 patients had recurrent ventricular tachyarrhythmias (1 7 with recurrent ventricular tachycardia and 2 with recurrent fascicular tachycardia). Flecainide was administered during tachycardia (over 5 to 10 minutes) to all patients with atrial flutter, to 10 patients with atrial fibrillation, and to 17 patients with ventricular tachyarrhythmias. In the remaining 3 patients with ill-sustained arrhythmias flecainide was administered during sinus rhythm and reinitiation of tachycardia was then attempted. Flecainide restored sinus rhythm in only 2 patients with atrial flutter (20%), in 9 patients with atrial fibrillation (90%), in 12 patients with ventricular tachycardia (SO%), and in one of the 2 patients with fasicular tachycardia. Flecainide also successfully terminated the left atrial tachycardia. Two patients experienced proarrhythmic side effects during flecainide administration, one of whom required intervention by cardioversion. Minor dose effects included oral paresthesia. transient drowsiness or dizziness, and occasional visual blurring. Flecainide acetate is an effective antlarhythmic agent for the acute termination of recent onset paroxysmal atrial and ventricular tachyarrhythmias.Present affiliations:

New implantable devices are now available that can offer different therapies for different arrhythmias but they need a method of discriminating between these rhythms. Heart rate analysis is predominantly used to discern between sinus rhythm (SR) and pathological tachycardias but this may be of limited value when the rates of the rhythms are similar. An enhanced form of Gradient Pattern Detection (GPD) has been developed using an 8-bit microcomputer that can distinguish between SR and up to three other arrhythmias in real time. This is a method based on electrogram morphology where each rhythm's specific electrogram is classified by a sequence of gradient 'zones'. The microprocessor of the computer is of similar processing power to ones used in current pacemakers. Five patients with multiple arrhythmias were studied. Four had ventricular tachycardia (VT) and one had three conduction patterns during supraventricular tachycardia (SVT). Bipolar endocardial right ventricular electrograms were recorded during SR and tachycardia in all patients. The computer would first 'learn' about each different rhythm by a semi-automatic means. Once all the rhythms were learned the program would enter the GPD analysis phase. The computer would output a series of real-time rhythm specific marker codes onto a chart recorder as it recognized each rhythm. Sixteen different arrhythmias (13 VT, 3 SVT) were examined for this study. All rhythms (including SR) were distinguished from each other except in the case of one patient with six VTs where two VTs had identical shapes and therefore could not be detected apart. The method would be a useful addition to heart rate analysis for future generations of microprocessor assisted pacemakers.