DOUBLE-LOOP FIGURE-OF-8 REENTRY AS THE MECHANISM OF MULTIPLE ATRIOVENTRICULAR NODE REENTRY TACHYCARDIAS

Seven patients with multiple atrioventricular node reentry tachycardia were analyzed to unravel the mechanism of these tachycardias. Six of the seven patients showed anterograde dual atrioventricular node pathw ays and one showed anterograde conduction through the fast pathway. Th ree types of retrograde pathways were noted among these seven patients : (1) the fast pathway with the earliest atrial activation at the His bundle area; (2) the intermediate pathway with the earliest atrial act ivation at the ostium of the coronary sinus; and (3) the slow pathway with the earliest atrial activation at the ostium of the coronary sinu s. All seven patients : used the intermediate pathway for retrograde c onduction. However, one patient showed evidence of retrograde slow pat hway conduction with demonstrable retrograde dual pathways, and anothe r showed evidence of retrograde fast pathway conduction with a shift o f atrial activation sequence when conduction switched to the intermedi ate pathway. Four different types of reentry circuits using either the fast or the slow pathway as the anterograde limb and one of the three retrograde pathways as the retrograde limb were demonstrated in these seven patients, resulting in two types of tachycardias in four patien ts and three types of tachycardias in three patients. A change in tach ycardia type could be induced with atrial or ventricular stimulation. A radiofrequency current delivered to the interior aspect of Koch's tr iangle along the tricuspid anulus in five patients resulted in selecti ve ablation or modification of the intermediate pathway or the slow pa thway, with preservation of anterograde atrioventricular conduction an d abolition of tachycardias. The findings suggest that a double loop f igure-of-8 reentry circuit including a fast pathway, a slow pathway, a nd an intermediate pathway is responsible for multiple atrioventricula r node reentry tachycardias. (AM HEART J 1994;127:83-95.)