ALTERATIONS OF ORTHODROMIC CIRCUS MOVEMENT TACHYCARDIA BY DUAL ATRIOVENTRICULAR NODAL PATHWAYS IN A PATIENT WITH WOLFF-PARKINSON-WHITE SYNDROME

In a patient with a left sided accessory pathway (AP) three different types of orthodromic circus movement tachycardia were observed: (1) na rrow QRS complex tachycardia with a stable cycle length (CL); (2) wide QRS complex tachycardia with a functional bundle branch block ipsilat eral to the AP, which, paradoxically, had a shorter CL. The decrease i n CL was due to a decrease of the AH interval; and (3) narrow QRS comp lex tachycardia with alternating CL, due to alternations of the AH int erval. These phenomena were attributed to a concomitant dual atriovent ricular (AV) node, which was eventually proven after successful cathet er ablation of the AP.