EARLY AFTERDEPOLARIZATIONS IN A PATIENT WITH IDIOPATHIC MONOMORPHIC RIGHT-VENTRICULAR TACHYCARDIA

To identify the role of after depolarizations in the induction of idio pathic monomorphic right ventricular tachycardia (VT), monophasic acti on potentials (MAPs) were recorded in a patient with this type of VT. The VT had a left bundle branch block configuration and inferior axis, and originated in the right ventricular outflow tract (RVOT). MAPs we re recorded with a contact electrode at the origin of the VT, as well as other ventricular sites. The VT was induced by the intravenous admi nistration of isoproterenol and/or rapid ventricular pacing and was pr eceded by short-long-short sequences of RR intervals. Early after depo larizations (EADs) in MAPs were recorded at the origin of VT (RVOT), b ut not recorded at other ventricular sites. These data suggest that ca techolamine sensitive triggered activity seems to be the mechanism of idiopathic monomorphic right VT and EADs can be recorded in associatio n with the occurrence of this type of VT.