VENTRICULAR-TACHYCARDIA WITH NARROW QRS DURATION, A RIGHT BUNDLE-BRANCH BLOCK PATTERN, AND RIGHT AXIS DEVIATION ABOLISHED BY CATHETER MANIPULATION

A 25-year-old woman underwent electrophysiologic evaluation for sustai ned normal QRS complex tachycardia with a pattern of right bundle bran ch block and right axis deviation. Ventricular tachycardia was diagnos ed by demonstrating fusion beats, atrioventricular dissociation, and b undle of His potential activation, which began before the onset of eac h QRS complex. A single ventricular extrastimulus was capable of easil y provoking the tachycardia. There was an inverse relationship between the coupling interval of the first extrastimulus and the interval of the first tachycardia beat, suggesting reentry as the mechanism. The t achycardia was unexpectedly abolished during catheter manipulation in the left ventricle and has never recurred during 1 year of follow-up e valuation. The tachycardia was thought to be an unusual form of interf ascicular tachycardia or microreentrant fascicular tachycardia.