Flecainide acetate in the treatment of tachycardias associated with Mahaim fibres

Patients with Mahaim fibres are susceptible to tachycardiaswhich can be refractory to conventional drug therapy, leadingto treatment with surgery and catheter ablation. The effectsof flecainide acetate were studied in 3 patients (61, 21 and35 years of age) with Mahaim fibres presenting with tachycardiasrefractory to beta-blockers, quinidine and verapamil. One alsohad ophthalmic side-effects from amiodarone. Three types oftachycardias were induced: a reentrant tachycardia with leftbundle branch block morphology (LBBBM) in all 3 patients, atrialflutter in one and atrial fibrillation in another. Intravenousflecainide acetate (2 mg kg–1) terminated reentrant tachycardiaand abolished duality of atrioventricular conduction in patient1. In patient 2, it abolished preexcitation during atrial flutterprior to termination. Atrial fibrillation could not be inducedin patient 3 after flecainide acetate. In all patients, retrogradeconduction was blocked, preexcitation was not present with atrialpacing and no tachycardia was induced after flecainide. Allhave remained asymptomatic on oral flecainide acetate (100 mgbd) for a mean follow-up period of 9 months. We conclude that (1) flecainide acetate is effective for thetreatment of various tachycardias associated with Mahaim fibres;(2) since different mechanisms responsible for the tachycardiawith LBBBM may be present in the same patient and difficultto determine in some, treatment with flecainide acetate whichaffects both the atrioventricular node and Mahaim fibre conductionmay be appropriate for the condition and; (3) its use shouldbe considered before more aggressive therapies.