Analysis of the Anatomical Tachycardia Circuit in Verapamil-Sensitive Atrial Tachycardia Originating From the Vicinity of the Atrioventricular Node

BACKGROUND—Calcium channel–dependent tissue has been suggested to be involved in the circuit of verapamil-sensitive atrial tachycardia originating from the atrioventricular (AV) node vicinity (V-AT), but little information exists. METHODS AND RESULTS—To examine the tachycardia circuit of V-AT, a single extrastimulus was delivered during tachycardia to 10 sites of the intraatrial septumthe earliest atrial activation site; His bundle (HB) site; 3 arbitrarily divided sites on the AV junction extending from the HB site to the coronary sinus ostium (CSOS) (sites S, M, and I); the internal-CSOS, inferior-CSOS, superior-CSOS, posterior-CSOS, and posteroinferior-CSOS in 10 patients with V-AT. The longest coupling interval that reset V-AT and subsequent return cycle were measured. The longest coupling interval at earliest atrial activation site was significantly longer than the longest coupling interval at the HB site, site S, M, and I, internal-CSOS, inferior-CSOS, superior-CSOS, posterior-CSOS, and posteroinferior-CSOS, respectively (P