Wide QRS tachycardia: multiple mechanisms in a patient after myocardial infarction

A 34-year-old man was hospitalized for extensive antero-apical myocardial infarction. Eight weeks after discharge from the hospital, he had intermittent rapid palpitations. During several episodes, a rapid, regular, wide-QRS-complex tachycardia with left bundle branch (LBB) morphology was recorded. All antiarrhythmic agents administered to the patient were unsuccessful in alleviating his symptoms, which were thought to be due to supraventricular tachycardia (SVT) with aberration. An electrophysiologic study was performed and revealed three morphologically distinct types of wide complex tachyarrhythmias: 1) Tachycardia 1 was determined to be A-V re-entry with antegrade conduction utilizing the normal A-V conducting system and retrograde conduction over a concealed accessory pathway located in the left A-V groove; 2) tachycardia 2 was identified as ventricular tachycardia (VT); and 3) tachycardia 3 was considered to be a second morphologic type of ventricular tachycardia as the morphology was identical to some of the episodes documented clinically. The patient was treated with oral amiodarone which was unsuccessful until combined with quinidine; this regimen has suppressed recurrence of VT during a four-month period of follow-up. The occurrence of wide-QRS-complex tachycardia in this patient immediately suggested the diagnosis of VT, but our other findings were unexpected. This case illustrates the need for considering all possible mechanisms when seeking to manage tachyarrhythmias, even if the diagnosis appears obvious.