# Impact of Low Voltage Threshold Adjustment on Activation Mapping Interpretation for Atrial Tachycardia in Low-Voltage Left Atrium

## TL;DR

Adjusting low voltage thresholds in heart mapping can reveal hidden electrical pathways in patients with low-voltage atria, improving ablation success for atrial tachycardia.

## Contribution

Demonstrates that low voltage threshold adjustment improves activation mapping accuracy in low-voltage left atria, guiding more effective ablation strategies.

## Key findings

- Adjusting low voltage thresholds revealed hidden conduction patterns in 25 of 55 tachycardias.
- Effective ablation was achieved in 94% of cases where mapping changed after threshold adjustment.
- Median follow-up showed a 69.3% freedom from tachycardia recurrence.

## Abstract

The misinterpretation of activation propagation within low
voltage zone (LVZ) can complicate atrial tachycardia (AT) mechanism analysis,
especially in patients with remodeled atrial substrate. This study investigated
the impact of low voltage threshold adjustment (LVTA) on left atrial (LA)
tachycardia activation mapping interpretation.

We identified 55
ATs in 42 patients undergoing catheter ablation for LA tachycardia, with a mean
LA voltage of <0.5 mV. Activation mapping of LA or both atria was used to
evaluate AT mechanisms before and after LVTA. Patients underwent regular clinic
follow-up after the procedure.

Comparing activation mapping
before and after LVTA revealed four categories: (1) complete change in AT circuit
and ablation design in 9 ATs; (2) an unchanged AT circuit but tailored ablation
design in 16 ATs; (3) identification of bystander gaps in 3 ATs; (4) an unchanged
AT circuit and ablation design in 27 ATs. Effective ablation, defined as AT
termination or circuit change, was obtained in all 9 Type 1 ATs and 15 of 16 Type
2 ATs by targeting the critical area identified by activation mapping after LVTA.
After a median follow-up of 16.5 months, the cumulative freedom from AT was
69.3%.

In patients with low LA voltage, conduction
propagation hidden within LVZ was not uncommon, but is often excluded from
activation mapping. LVTA can uncover this subtle conduction propagation with
reliable accuracy, improving the veracity of activation mapping, and helping
guide subsequent ablation.