ADENOSINE-SENSITIVE VENTRICULAR-TACHYCARDIA FROM THE ANTEROBASAL LEFT-VENTRICLE

Objectives. This study demonstrates that exercise-provocable tachycard ia resembling right ventricular outflow tract tachycardia may originat e from the anterobasal left ventricle, Background. Reentry is the oper ative mechanism of idiopathic left ventricular tachycardia, with a QRS complex of right bundle branch block and superior axis that is respon sive to verapamil but not adenosine, Whether some mechanism other than reentry is operative in some idiopathic left ventricular tachycardias is unclear. Methods, In 4 of 53 consecutive patients with idiopathic left ventricular tachycardia, the tachycardia was sensitive to adenosi ne, These four patients were women 63, 61, 61 and 31 years old and wer e the subjects of the present study, Results. In all four patients, sp ontaneous tachycardia was related to exercise or emotional stress, The tachycardia displayed atypical left (one patient) or right (three pat ients) bundle branch block with an inferior axis and marked variation in cycle length, An intravenous bolus of adenosine triphosphate (10 to 20 mg) terminated tachycardia in all four patients, Tachycardia was t erminated or prevented in three patients given intravenous or oral ver apamil, Atrial or ventricular incremental or extrastimulus testing ind uced tachycardia in all four patients (three with, one without isoprot erenol infusion), Electrically induced tachycardia also demonstrated m arked variation in cycle length, which ranged from 230 to 390 ms, Entr ainment was not demonstrable with overdrive pacing from multiple sites , Endocardial mapping during tachycardia revealed that the earliest ac tivations were registered 25, 40, 35 and 50 ms before onset of the QRS complex, respectively, from the anterior aspect of the left ventricle just below the mitral annulus, adjacent to the left ventricular outfl ow tract, High frequency Purkinje spikes were not recorded at this sit e, Radiofrequency current delivered to this site successfully ablated the tachycardia in three of the four patients. Conclusions, Exercise-p rovocable, catecholamine mediated, verapamil-responsive, adenosine-sen sitive ventricular tachycardia may arise from the anterobasal left ven tricle adjacent to the outflow tract. (C) 1997 by the American College of Cardiology.