Atrial tachycardia originating at the tricuspid annulus.

We report a patient with re-entrant atrial tachycardia that originated at the inferolateral tricuspid annulus. Single atrial extra-stimulation reproducibly induced the atrial tachycardia with an inverse relationship between the coupling interval of extra-stimulation and the return cycle of the first tachycardia beat. A real-time three-dimensional electroanatomical mapping showed focal atrial activation spreading semi-radially from the tricuspid annulus. The tachycardia was successfully eliminated by radiofrequency ablation at the earliest atrial activation site, preceding by 27 ms the arbitrary determined onset of surface P wave. An accelerated atrial rhythm with similar P-wave morphology to that of the tachycardia was observed at the successful ablation site during radiofrequency application. The mechanism of this tachycardia seems to be due to re-entry originating in or around the possible accessory atrioventricular node without ventricular connection.