NORMAL LEFT-VENTRICULAR FUNCTION DOES NOT PROTECT AGAINST PROPAFENONE-INDUCED INCESSANT VENTRICULAR-TACHYCARDIA

Propafenone is a class Ic anti-arrhythmic agent with mild beta-blockin g properties which has recently become available in South Africa. We h ave used the drug in 3 patients with sustained monomorphic ventricular tachycardia not due to ischaemic heart disease. All had normal left v entricular function; 1 had Wegener's granulomatosis and 2 had arrhythm ogenic right ventricular dysplasia. In the latter 2, propafenone provo ked incessant monomorphic ventricular tachycardia which persisted for more than 24 hours despite repeated efforts at termination. The morpho logy was similar to the patients' spontaneous ventricular tachycardia, but the rate was slower and the QRS complexes broader, consistent wit h propafenone's marked ability to slow intraventricular conduction. It is postulated that incessant tachycardia results from perpetuation of re-entry due to marked conduction slowing produced by the drug. Previ ous reports have suggested that this is most likely to occur in patien ts with poor left ventricular function, but our experience indicates t hat those with normal left ventricular function are also at risk, part icularly if the substrate for reentry is present. Propafenone, like al l other powerful antiarrhythmic agents, may provoke life-threatening a rrhythmias and should be used with great caution after due considerati on of the indications, even in patients with normal left ventricular f unction.