High-density contact and noninvasive mapping of focal atrial tachycardia: Evidence of dual endocardial exits from an epicardial focus.

We report a case of recurrent focal atrial tachycardia (AT) which mechanisms could be resolved by using noninvasive electrocardiographic imaging (ECGI) reconstructing epicardial potentials and rapid high-density endocardial contact mapping (Rhythmia™, Boston Scientific, Natick, MA, USA). ECGI demonstrated focal activity from the anterior of the left superior pulmonary vein antrum, although Rhythmia™ showed focal activity from the high anterior left atrium with the 2nd focus originating from the site where identical to the focus on the ECGI map with slightly delay (by 8 ms). Elimination of the AT by radiofrequency applications for both of the endocardial focuses indicated the dual endocardial exits from an epicardial focus.