The mechanisms of left septal and anterior wall reentrant atrial tachycardias analyzed with ultrahigh resolution mapping: The role of functional block in the circuit.

BACKGROUND

Low voltage areas (LVAs) are most commonly observed on the left atrial (LA) septal/anterior wall.

OBJECTIVE

We explored the mechanisms of LA septal/anterior wall reentrant tachycardias (LASARTs) using ultrahigh resolution mapping.

METHODS

This study included seven consecutive LASARTs in six patients (75 [62.2-82.8] years, 4 women) who underwent atrial tachycardia (AT) mapping and ablation using Rhythmia systems.

RESULTS

The AT cycle length was 266 (239-321) ms. During ATs, 11.0 (9.0-12.9) cm of LVAs were identified in all, and 0.8 (0.7-1.7) cm of dense scar was identified in four patients. Five ATs rotated around dense scar, while two rotated around functional linear block, which was confirmed during atrial pacing after AT termination. The AT circuit length was 8.7 ± 2.1 cm with a conduction velocity of 30.4 ± 3.7 cm/s. A median of 3.0 (2.0-4.0) slow conduction areas per circuit were identified, and 17/23 (73.9%) areas were present in LVAs, while they were at the border of the LVA and normal voltage areas in the remaining 6/23 (26.1%). Global activation histograms facilitated the identification of the critical isthmus in all. Tailor-made ablation at critical isthmuses successfully eliminated all ATs. However, one patient with AT related to functional linear block experienced recurrent AT related to dense scar, which progressed after the procedure. During a mean 14 ± 13 month follow-up after the last procedure, no patients experienced recurrent ATs without any complications.

CONCLUSION

LASARTs consist of not only fixed conduction blocks but also functional conduction blocks. Ultrahigh resolution mapping is highly useful to decide the optimal tailor-made ablation strategy based on the mechanisms.