Cardioversion of A-V nodal tachycardias

Cardioversion was attempted in 10 patients with proved A-V nodal tachycardias. Four patients with presumably digitalis-induced tachycardias failed to convert, but responded to intravenous potassium. The absence of adverse reactions in these patients is tentatively ascribed to the protective effects of the potassium ion. In contrast to the glycoside-induced arrhythmias, spontaneous A-V nodal tachycardias responded to therapeutic electrical discharge. Cardioversion should not be used in digitalisinduced arrhythmias, for it is ineffective and even potentially harmful. However, ventricular fibrillation triggered by extrasystoles falling in the vulnerable phase (R on T phenomenon) can be converted by electric discharge. Cardioversion is still the treatment of choice of ventricular fibrillation even when it occurs in a digitalized patient.