Novel form of atrial tachycardia originating at the atrioventricular annulus

We report two patients with reentrant atrial tachycardia that originated at the AV annulus. Atrial tachycardia originated in the posterior portion of mitral annulus in one patient (case I) and the posterolateral portion of tr icuspid annulus in one patient (case 2). Tachycardia was successfully elimi nated by RF catheter ablation in both patients, with the catheter placed un derneath the mitral valve in case 1 and on the tricuspid annulus in case 2. Spiky potentials were recorded in the diastolic phase of the atrium during tachycardia at the sites of successful ablation. Spiky potentials were als o recorded after atrial electrogram during sinus rhythm, and showed decreme ntal properties during atrial pacing. An accelerated atrial rhythm rr as ob served during RF application, and tachycardia could not be induced after ab lation in either patient. Tachycardia in these patients seemed to be due to reentrant tachycardia originating in the accessory AV node (Mehaim fiber) without ventricular connection.