A simple algorithm for defining the mechanism and the chamber of origin in atrial tachycardias

Although macroreentrant atrial tachycardia (MRAT) and focal atrial tachycardia (FAT) can be successfully cured by catheter ablation, the proper diagnosis and treatment of these arrhythmias can still be challenging.

The objective of this study is to develop an algorithm allowing rapid diagnosis of the mechanism and the chamber of origin of atrial tachycardia based on intracardiac catheter recordings from the right atrium and the coronary sinus (CS).

A 2-stepped algorithm was designed: (1) The time of biatrial activation expressed as a percentage of the tachycardia cycle length served to discriminate FAT from MRAT. (2) In FAT, the direction of activation of the CS catheter and the earliest atrial activation were used to define the chamber of origin. In MRAT, the time of right atrium activation was determined or entrainment was used at different sites. Thirty-two intracardiac recordings were reviewed off-line after the algorithm by 4 electrophysiologists blinded to the mechanism and the chamber of origin. The results of their analysis were compared with the intraoperative diagnosis.

The algorithm correctly identified 11 (100%) of 11 FATs and 19 (90.4%) of 21 MRATs. The site of origin was correctly identified in 8 (72.7%) of 11 FATs and in 20 of 21 (95.2%) MRATs. The site of origin was misidentified in 3 FATs, all arising from the CS ostium.

This algorithm allows rapid discrimination between FAT and MRAT. The chamber of origin is detected with a high accuracy in MRAT. However, the earliest atrial activation taken as an isolated event is not a good predictor for the chamber of origin in FAT arising from the ostium of the CS.