# Modified stepwise method with the guidance of QDOT MICRO catheter for mitral isthmus ablation in patients with persistent atrial fibrillation

## TL;DR

A new method using a QDOT MICRO catheter improves the efficiency and effectiveness of mitral isthmus ablation in patients with persistent atrial fibrillation.

## Contribution

The modified stepwise method with QDOT MICRO catheter reduces ablation time and points while improving block rates.

## Key findings

- The QDM group had significantly shorter operation and ablation times compared to the STSF group.
- The QDM group achieved higher conduction block rates with fewer ablation points.
- The QDM method reduced the need for epicardial ablation in mitral isthmus procedures.

## Abstract

Ethanol infusion of the vein of Marshall (EI-VOM) has elevated the success rate of mitral isthmus (MI) block in patients with persistent atrial fibrillation (PeAF). However, the procedure involve the extensive endocardial ablation and epicardial ablation, which brought the operational difficulty and risk.

Patients with PeAF were randomly assigned in a 1:1 ratio to either STSF catheter group using the stepwise method (STSF group) or QDM catheter group using a modified stepwise method (QDM group) for MI ablation. The modified stepwise method was as follows: step 1, The potential of VOM was mapped from endocardium using the QDM catheter. Step 2, EI-VOM. Step 3, precise endocardial ablation guiding by VOM potential. Step 4, QDM catheter was cannulated into the CS for epicardial ablation, especially the ostium of Marshall. The immediate procedural results were compared between the two groups.

After excluding 5 patients with unsuccessful EI-VOM, 68 patients were divided into STSF group (36 cases) and QDM group (32 cases). The potential of VOM could be clearly mapped from endocardium using a QDM catheter. Both the accumulated operation time (p = 0.032) and ablation time (p < 0.001) were significantly shorter in the QDM group compared to the STSF group. QDM group achieved more conduction blocks of MI after a single endocardial line ablation (71.9% vs. 36.1%, p = 0.017) with fewer ablation points (p < 0.001) compared to the STSF group. The block rate of the MI after endocardial ablation alone was also higher in the QDM group than in the STSF group (90.6% vs. 69.4%; P = 0.019), which avoided epicardial ablation. Even if epicardial ablation is necessary, the number of ablation points on the epicardial surface in the QDM group would be fewer than in the STSF group (p < 0.001).

The QDM catheter can be used to map the potential of VOM from endocardium, thereby facilitating precise endocardial mitral isthmus linear ablation. The modified stepwise approach effectively reduces the number of endocardial ablation points and the likelihood of requiring epicardial ablation. (NCT06145906, ClinicalTrial.gov).