Global right atrial mapping of human atrial flutter: The presence of posteromedial (sinus venosa region) functional block and double potentials - A study in biplane fluoroscopy and intracardiac echocardiography

Background-Previous studies of atrial flutter have found linear block at th e crista terminalis: this was thought to predispose the patient to the arrh ythmia, More recent observations, however, have demonstrated crista conduct ion. We sought to characterize the posterior boundary of atrial flutter. Methods and Results-Patients with counterclockwise flutter (n=20), clockwis e flutter (n=3), or both (n=5) were studied using two 20-pole catheters. Bi plane fluoroscopy determined catheter positions. During counterclockwise fl utter, craniocaudal activation occurred along the entire lateral and poster ior right atrial walls. Septal activation proceeded caudocranially. In all patients, a line of block was seen in the posteromedial (sinus venosa) righ t atrium, this was manifested by the presence of double potentials where th e upward and downward activations collided. Anatomic location was confirmed by intracardiac echocardiography in 9 patients. In patients with clockwise flutter, the line of block and double potentials were seen in the same loc ation during counterclockwise nutter, but the activation sequence around th e line of block was reversed. Pacing near the site of double potentials dur ing sinus rhythm excluded a fixed line of block, and premature atrial compl exes demonstrated functional block with manifest double potentials. In 2 pa tients, posterior ectopy organized to subsequently initiate isthmus-depende nt atrial flutter. Conclusions-(1) A functional line of block is seen at the posteromedial (si nus venosa region) right atrium during counterclockwise and clockwise atria l flutter. (2) All lateral wall right atrial activation can be uniform duri ng flutter, without linear block or double potentials in the region of the crista terminalis. (3) Activation at the site of posteromedial right atrial functional block can organize to subsequently initiate isthmus-dependent a trial flutter.