Elsevier

Heart Rhythm

Volume 16, Issue 11, November 2019, Pages 1652-1660
Heart Rhythm

Clinical
Imaging/Mapping
Insights from atrial surface activation throughout atrial tachycardia cycle length: A new mapping tool

https://doi.org/10.1016/j.hrthm.2019.04.029Get rights and content

Background

A novel “LUMIPOINT” software in the Rhythmia system (Boston Scientific) displays a histogram of activated area over the entire atrial tachycardia (AT) cycle length (CL) with a normalized score.

Objective

The purpose of this study was to examine whether the pattern of this global activation histogram (GAH) identified reentrant vs focal AT and whether a decrease in atrial activation area, shown as valleys in the GAH, identifies isthmuses.

Methods

One hundred eight activation maps of ATs (17 focal, 57 macroreentrant, 21 localized, 13 multiple loop) in 67 patients were reviewed retrospectively with the LUMIPOINT software. The ACTIVATION SEARCH feature highlighted the activated area in a given time period irrespective of the activation map. A 30-ms unit time interval was set, and the GAH patterns and electrophysiological properties of highlighted areas were examined.

Results

Focal ATs systematically displayed a plateau with GAH-Score <0.1 for at least 30% of the CL. Most reentrant ATs (90/91 [98.9%]) lacked this plateau and displayed activity covering the entire CL, with 2 [1–2] GAH-Valleys per tachycardia. Each GAH-Valley highlighted 1 [1–2] areas in the map. Among 264 highlighted areas, 198 (75.0%) represented slow conduction, 19 (7.2%) lines of block, 27 (10.2%) wavefront collision, 3 (1.1%) unknown, and 17 (6.4%) absence of activation in focal ATs. Practical ablation sites all matched one of the highlighted areas based on GAH-Valleys, and they corresponded better with areas highlighted by GAH-Score ≤0.2 (P <.0001).

Conclusion

GAH shows focal vs reentrant mechanisms at first glance. Decrease in activated areas (displayed by GAH-Valleys) is mostly due to slow conduction and highlights areas of special interest, with 100% sensitivity for isthmus identification.

Introduction

Atrial tachycardia (AT) is frequently observed in the context of atrial fibrillation (AF) ablation, due to both substrate and ablation scars.1, 2, 3 Demonstrating the entire AT circuit with entrainment mapping alone may be challenging4 Improvement in mapping systems and catheters now allows mapping with sufficient resolution to demonstrate the precise activation sequence of these complex ATs,5, 6, 7, 8 However, mapping systems still struggle with complex electrograms (EGMs), and this may impact activation maps.9 LUMIPOINT is a novel set of software features in the Rhythmia mapping system (Boston Scientific, Marlborough, MA) centered around an algorithm that detects all activations present in every EGM irrespective of local activation time.10 The activated atrial surface area in a given time-of-interest period through the entire cycle length (CL) may be shown. In addition, SKYLINE is a tool that displays a full chamber activation in an intuitive 2-dimensional trace with the histogram of the atrial surface activation throughout the AT CL. Peaks in the histogram are seen when a large part of the atrium is activated, whereas valleys correspond to a smaller surface of activation. Theoretically, this valley in the histogram may correspond to the isthmus of the tachycardia circuit.

We studied whether histograms of focal ATs differ from those of reentrant ATs, and whether valleys in the histogram indicate practical ablation sites. We also systematically investigated the mechanisms corresponding to these valleys.

Section snippets

Study population

We prospectively examined 85 consecutive AT patients undergoing ablation guided by high-density mapping with the Rhythmia system in our center between November 2014 and December 2015. Of these patients, 67 who had at least 1 complete activation map during the procedure were included in the study. All patients gave written informed consent according to the institutional guidelines of the University of Bordeaux Health System with ethical approval for the study.

Electrophysiological study and mapping with Rhythmia

Antiarrhythmic medications were

Patient and AT characteristics and outcomes

The baseline characteristics of the 67 patients are listed in Table 1 and AT characteristics in Table 2. Fifty patients (74.6%) had ATs after AF ablation, with a mean of 1.6 ± 1.3 procedures. Among them, 108 ATs were mapped with the Rhythmia mapping system and diagnosed as focal AT (n = 17), macroreentrant AT (n = 57), localized reentry (n = 21), or multiple-loop reentry (n = 13). The multiple-loop reentries in this study were all dual-loop reentries. Activation maps of 14,307 ± 6917 points

Major findings

In the present study, we demonstrated the following. (1) The GAH pattern of focal ATs is typical, with a plateau (no activation) >30% of the CL with GAH-Score <0.1, allowing for instant diagnosis. (2) GAH-Valleys are due to activation of a limited surface area and mostly correspond to slow conduction. However, lines of block and wavefront collision may also be seen. (3) Approximately 80% of slow conduction areas highlighted based on GAH-Valleys occur within the AT circuits, thereby identifying

Conclusion

The LUMIPOINT GAH shows focal vs reentrant mechanisms at first glance. Decrease in atrial activation area is mostly due to slow conduction and highlights areas of special interest, with sensitivity of 100% for practical ablation sites.

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    This, however, would be different from a value of zero, which would indicate the absence of any activity between 2 consecutive activations, as expected in a focal source. We originally defined this value as “GAH score” in this study following the previous article.19 Based on the LUMIPOINT-SKYLINE as shown in Figure 2, the lowest GAH score (Figure 2A), duration of GAH score < 0.1 (Figure 2B), duration of the plateau in GAH score < 0.1 (Figure 2C) were measured and the duration of GAH score < 0.1/TCL ratio and the duration of the plateau in GAH score < 0.1/TCL ratio were calculated.

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    The amount of points per bar represents the segmental activated area of the left atrium with the same LAT (1/20 TCL). We classified a valley in the LAT histogram (LAT-valley) as a section of the plot with 20% or less recorded points than the maximum LAT value (highest bar).9 To accept this section as a zone of slow conduction, it should contain at least 10% of the TCL.10

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    Beyond voltage mapping (discussed previously), UHD activation mapping (in AT or sinus rhythm [SR]) provides considerable help in identifying the substrate of AT (ie, incision lines [Fig. 3]) as well as for validating block across previously created ablation lines.25 Automatic detection of double potential EGM and diatolic potentials are near-future software improvements that will be available (Lumipoint embedded in Rhythmia [Fig. 4]).26,27 The Carto 3 system (v6) with the HD coloring feature provides improved visualization of propagation.

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This research was partly funded by a grant from Investments of the Future: IHU LIRYC ANR-10-IAHU-04. Drs Haïssaguerre, Hocini, Jaïs, and Sacher have received lecture fees from Biosense Webster and Abbott. Drs Denis, Derval, Jaïs, and Sacher received speaking honoraria and consulting fees from Boston Scientific. Mr Jean-Rodolphe Roux is an employee of Boston Scientific. All other authors have reported that they have no conflicts relevant to the contents of this paper to disclose.

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