Focal Atrial Tachycardia Arising from the Tricuspid Annulus: Electrophysiologic and Electrocardiographic Characteristics

INTRODUCTION: Focal right atrial tachycardia (RAT) arising from the crista terminalis, para-Hisian, and coronary sinus os regions are well described. Less information exists regarding RAT arising from the nonseptal region of the tricuspid annulus (TA). METHODS AND RESULTS: From a consecutive series of 64 patients who had undergone successful radiofrequency ablation (RFA) of 67 RATs, the characteristics of 9 (13%) patients (6 men; mean age 50 +/- 20 years) with a TA focus were reviewed. The annular focus was localized to the inferoanterior TA in 7 and the superior TA in 2. Mean tachycardia cycle length was 371 +/- 66 msec. Mean activation time at the site of successful RFA in 9 of 9 patients was -43 +/- 11 msec. At 9.3 +/- 5.6 months of follow-up, 1 of 9 patients had recurrent tachycardia successfully treated with repeat RFA. In 7 of 9 patients with RAT from the inferoanterior TA, the surface ECG P wave morphology was upright in aVL, inverted in III and VI, and either inverted or biphasic with an initial negative deflection from V2 to V6. CONCLUSION: The TA is an important site of origin of RAT. In the present study, the inferoanterior region of the TA was a preferential site of origin with resulting characteristic P wave morphology. Knowledge of this anatomic distribution and P wave morphology allows targeted mapping and may facilitate successful RFA.