“Cristal Tachycardias”: Origin of Right Atrial Tachycardias From the Crist Terminalis Identified by Intracardiac Echocardiography

Objectives. We sought to use intracardiac echocardiography (ICE) to identify the anatomic origin of focal right atrial tachycardias and to define their relation with the crist terminalis (CT). Background. Previous studies using ICE during mapping of atrial flutter and inappropriate sinus tachycardi have demonstrated an important relation between endocardial anatomy and electrophysiologic events. Recent studies have suggested that right atrial tachycardias may also have characteristic anatomic distribution. Methods. Twenty-three consecutive patients with 27 right atrial tachycardias were included in the study. ICE was used to facilitate activation mapping in relation to endocardial structures. 20-pole catheter was positioned along the CT under ICE guidance. ICE was also used to assist in guiding detailed mapping with the ablation catheter in the right atrium. Results. Of 27 focal right atrial tachycardias, 18 (67%, 95% confidence interval [CI] 46% to 83%) were on the CT (2 high medial, 8 high lateral, 6 mid and 2 low). ICE identified the location of the tip of the ablation catheter in immediate relation to the CT in all 18 cases. The 20-pole mapping catheter together with echocardiographic visualization of the CT provided guide to the site of tachycardi origin along this structure. Radiofrequency ablation was successful in 26 (96%) of 27 (95% CI 81% to 100%) right atrial tachycardias. Conclusions. This study demonstrates that approximately two thirds of focal right atrial tachycardias occurring in the absence of structural heart disease will arise along the CT. Recognition of this common distribution may potentially facilitate mapping and ablation of these tachycardias.