Accuracy of pace-mapping using an automated template matching module for site of origin identification of idiopathic outflow tract premature ventricular contractions
Authors: Schaerli N , Ebert M , Wijnmaalen A P , Piers S R D , Kimura Y , Trines S A , Meretta A , Rademaker R , Zeppenfeld K , De Riva M 
Published: May 2024

Abstract

Background
Activation mapping (AM) is the preferred approach to identify the premature ventricular complexes (PVC) site of origin (SOO) but it is limited when PVCs are infrequent. Pace-mapping (PM) is often used in combination with AM. Yet, relying on PM as sole guide for ablation requires a high accuracy for detecting the PVC SOO. Limited data exists on the accuracy of automated PM using PASO™ for identifying the SOO of idiopathic PVCs, particularly in the left ventricular outflow tract (LVOT). In two cohorts with both idiopathic and non-idiopathic PVCs, a PASO™ &gt;94% was associated with ablation success.

Purpose
This study evaluated the accuracy of PM using the automated digital pace-matching module integrated in the CARTO mapping system for identifying the SOO of idiopathic outflow-tract PVCs. It also compared its accuracy in the LVOT versus the right ventricular outflow tract (RVOT).

Methods
Consecutive patients undergoing successful ablation of idiopathic outflow-tract PVCs were prospectively included. AM and PM were performed with a 3.5mm tip catheter. PM was conducted at 2mA, 5mA, or 10mA output, selecting the lowest output that captured at each site. Ablation was performed at the site of earliest bipolar local activation time. The PVC SOO was defined as the site of acute ablation success. The distance between the best PM (BPM) and the SOO and the areas defined by PM ≥98%, ≥96%, and ≥94% were measured. Long-term success was defined by a ≥80% reduction in PVC burden at 3-month follow-up.

Results
In total, 27 patients were included; 18 had PVCs from the RVOT and 9 from the LVOT. All procedures were acutely successful after a median of 2 (IQR 1-3) radiofrequency applications (RFA) in the RVOT and one (IQR 1-2) RFA in the LVOT. In the RVOT, the median BPM was 98.1% (98.0-98.6), the median distance from the BPM to the SOO was 3.5 mm (IQR 0–8.5mm) and the areas of PM ≥98%, ≥96%, ≥94% were 1.2cm2 (0.5 – 1.8), 3.4cm2 (1.5-4.7) and 7.1cm2 (4.9-11.1). In the LVOT, the median BPM was 95.5% (IQR 94.9 – 97.8%) and the median distance from the BPM to the SOO was 8 mm (IQR 2–15mm). Only 3/9 patients with LVOT PVCs had a BPM ≥96% (1/9 ≥98%) and in all 3, the PVC SOO was coincident with the BPM site. From the remaining 6 patients, 5 had a BPM ≥94% but only in 2/5 the PVC SOO was within the area defined by the BPM site. In 26/27 (96%) patients, no PVC recurrence was documented after 3 months (median burden 0% [IQR 0-0]).

Conclusions
The accuracy of using the best pace-match provided by PASO™ for identifying the PVC SOO in the RVOT is high, making it a suitable target for limited ablation when activation mapping is not possible because of insufficient PVCs. In the LVOT, the best pace-match is frequently lower than in the RVOT and it misses the PVC SOO in almost half of the patients. The previously suggested PM &gt;94% cut-off seems to be insufficient to identify the PVC SOO in both the RVOT and LVOT.TablePacemap