CLINICAL, ELECTROPHYSIOLOGICAL CHARACTERISTICS, AND RADIOFREQUENCY CATHETER ABLATION OF ATRIAL TACHYCARDIA NEAR THE APEX OF KOCHS TRIANGLE

Atrial tachycardia, with its focus near the apex of Koch's triangle, m ay carry a potential risk of atrioventricular block during radiofreque ncy catheter ablation. The efficacy and safety of this procedure have never been addressed. The characteristics and catheter ablation result s are reported for six patients with atrial tachycardia near the apex of Koch's triangle. All six-patients were female aged 49.6 +/- 9.3 yea rs (range 39-63). Organic heart disease was present in 3 (50%) of the 6 patients. The P wave in surface ECG had a mean axis of -28 degrees ( range -90 degrees - +30 degrees) in the frontal plane. The catheter ab lation was guided by activation sequence mapping. The energy was titra ted from low power level. Atrial overdrive pacing was used to monitor the atrioventricular conduction should accelerated junctional rhythm o ccur. At the final successful ablation site, the local atrial activati on was 41.8 +/- 9.1 ms before the P wave and His-bundle potential was present in 5 of the 6 patients. All patients had their atrial tachycar dia eliminated without recurrence or heart block during a follow-up pe riod of 17.7 +/- 8.5 months (range 6-30). In conclusion, atrial tachyc ardia near the apex of Koch's triangle has distinct clinical and elect rophysiological features. Radiofrequency catheter ablation can be perf ormed effectively. However, extreme care must be taken to prevent inad vertent atrioventricular block. Titrated energy application and contin uous monitoring of atrioventricular conduction are mandatory.