Activation mapping to determine the mechanism of atrial tachycardia when pacing techniques are not feasible

Atrial tachycardia/flutter (ATAF) could be sustained by a focus or a reentry circuit, which mapping differs significantly. Entrainment mapping is widely used to detect reentry, but it is not always feasible. We evaluated an activation mapping protocol to differentiate macro, micro-reentrant and focal ATAFs.

Among 454 patients who underwent ablation for supraventricular tachycardia (SVT) between December, 2004 and August, 2008, 52 ATAF patients were selected and assessed by means of activation mapping (study mapping protocol). The remaining 402 cases (AVNRT, AVRT, and common atrial flutter) were excluded.

Fifty-eight ATAF morphologies were mapped (mean CL 297.2±98 ms). The protocol identified the ATAF mechanism in 53/58 (91%, 52 successfully ablated) morphologies, while the mapping technique failed in 5/58 (9%) cases/patients. Among the 53 ATAF diagnoses, 25/53 (47%) were macroreentrant ATAFs (MATs), whereas 12/53 (23%) were focal ATAFs (FATs) or microreentrant ATAFs (MIATs) (16/53, 30%). Ablation was successful in 25/25 cases of the MAT group, in 11/12 (91.7%) cases of the FAT group, and in 16/16 cases of the MIAT group. At the end of the procedure, no ATAF was inducible in 44/52 (85%) patients. The study protocol was successfully validated in 20 patients (10 with AVNRT, and 10 with common atrial flutter) of the control group. After a mean follow-up of 21.5±12.5 months, 36/52 (70%) pts resulted free from ATAF. Non-inducibility predicted long-term freedom from ATAF (92.1 % vs. 60 %, P=0.005, OR 0.09; 95% CI 0.18-0.51, P=0.006).

Activation mapping alone may be reliable to determine the ATAF mechanism, especially when pacing techniques are not feasible.