Introduction

With CARTO HD COLORING, a new enhanced software-based map visualization is available to highlight among others potential areas of conduction block in complex arrhythmias (Extended Early Meets Late, EEML). In this part of the software, the user can set values for displaying early-meets-late and conduction block areas respectively. The values are displayed as percentage of the mapped tachycardia cycle-length (TCL).The ideal settings of thresholds are still unclear and are examined here by studying 12 left atrial arrhythmias.

Methods

10 patients with 12 left atrial tachycardias underwent high-density activation mapping of the left atrium. Areas of local conduction block were visualized with different Extended Early Meets Late (EEML) thresholds (75/25 %; 80/20 %; 85/15 %) and compared to ripple maps for verification (Fig. 1,2). Ripple mapping was chosen as reference method due to its mostly operator- and annotation-independent processing. 
Inclusion criteria were: At least one complete map of a monomorphic left atrial tachycardia containing at least 2000 electroanatomic points obtained with a Pentaray multi-electrode catheter (Biosense Webster, Diamond Bar, CA, US) with a color threshold of 7 or lower with identification of at least one area of local conduction block with an EEML lower threshold of 25 %. 

Areas of local conduction block were visualized with different EEML-settings (75/25 %; 80/20 %; 85/15 %). For verification, areas of interest were compared to ripple maps. Local conduction vectors in between points were assessed visually to verify conduction block vs. slow conduction.

Fig. 1: Exemplaric distance measurement between displayed block and site of block by ripple mapping in different EEML-Settings


Fig. 2: Assessment of local conduction vectors by ripple mapping in comparison to displayed conduction block (75/25 % displayed here)

Results 

In 10 patients; 12 tachycardia maps were obtained and analyzed. All patients had previous extensive ablation procedures (PVI plus additional substrate modification with at least one linear lesion) performed. In all cases, areas of atrial low-voltage were identified. 

Detailed characteristics of maps and tachycardias are shown below (Tab. 1). In all 12 cases, areas of conduction block contributing to the tachycardia mechanism could be identified. Mean distances between the EEML-conduction block and the site defined by local conduction vectors using ripple mapping are shown below. 

In cases were EEML-values resulted in distances of >30 mm between both methods, typically by indicating complete conduction block throughout a large area, values are displayed as not available.

Settings of 80/20 % or 85/15 % were more accurate than 75/25 % in displaying the actual amount of conduction block as assessed by ripple maps (Fig. 3).




Fig. 3: Measured distances with different EEML-Settings; *=p<0,05

Conclusions

HD coloring leads to further insights into complex tachycardias through a new Voxel Map Surface Concept and color-based visualization of local conduction block. It can be assumed that individual adaption of Extended Early Meets Late (EEML) thresholds should be applied for a more accurate visualization of local conduction block.
Based on our experience, a suggested workflow is shown below.