Radiofrequency ablation of atrial tachycardia originating from the triangle of Koch.

Atrial tachycardia (AT) originating in the triangle of Koch is reported rarely and presents a potential risk of atrioventricular (AV) block during radiofrequency (RF) catheter ablation. Eight patients with AT in the triangle of Koch undergoing RF ablation are presented. There were five women and three men, ranging in age from 32 to 74 years. One patient had bicuspid aortic valve disease, and the other seven patients had no structural heart disease. At electrophysiological study, AT was inducible in all eight patients. In one patient, AV nodal re-entrant tachycardia was also inducible. The site of AT was located by recording the earliest atrial activation during AT and successful RF ablation. Fluoroscopy confirmed the corresponding site to the region of the triangle of Koch. The earliest atrial activation was 35+/-9 ms before the surface P wave, and was recorded at the apex of the triangle of Koch near the bundle of His in six patients and midway between the bundle of His and coronary sinus os in two patients. At the successful RF application site, His potential was not recorded in any patient. The mean AV ratio was 5:1 (range 1:1 to 12:1). RF ablation at the successful site resulted in accelerated junctional rhythm in four of the eight patients and successfully terminated AT in all eight patients, with first-degree AV block in one patient. In conclusion, AT from the triangle of Koch is a distinct entity and RF ablation can be successfully performed; however, a potential risk of AV block remains.