Standardized unfold mapping: a technique to permit left atrial regional data display and analysis
Standardized unfold mapping: a technique to permit left atrial regional data display and analysis
Steven E. Williams 0 1 2
Catalina Tobon-Gomez 0 1 2
Maria A. Zuluaga 0 1 2
Henry Chubb 0 1 2
Constantine Butakoff 0 1 2
Rashed Karim 0 1 2
Elena Ahmed 0 1 2
Oscar Camara 0 1 2
Kawal S. Rhode 0 1 2
0 PhySense, Universitat Pompeu Fabra , Barcelona , Spain
1 Translational Imaging Group, Centre for Medical Image Computing, University College London , London , UK
2 Division of Imaging Sciences and Biomedical Engineering, King's College London , 4th Floor North Wing, St. Thomas' Hospital , 249 Westminster Bridge Road, London SE1 7EH , UK
3 Steven E. Williams
Purpose Left atrial arrhythmia substrate assessment can involve multiple imaging and electrical modalities, but visual analysis of data on 3D surfaces is time-consuming and suffers from limited reproducibility. Unfold maps (e.g., the left ventricular bull's eye plot) allow 2D visualization, facilitate multimodal data representation, and provide a common reference space for inter-subject comparison. The aim of this work is to develop a method for automatic representation of multimodal information on a left atrial standardized unfold map (LA-SUM).
Atrial fibrillation; Catheter ablation; Cardiac magnetic resonance; Unfold map; Regional analysis; Contact-force analysis
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SEW and CTG contributed equally to this study.
What’s new
A new, standardized, two-dimensional left atrial unfold map (LA-SUM)
is developed allowing simultaneous visualization of all regions of the
left atrium.
Using the LA-SUM, a 24-region LA segmentation is proposed in order
to facilitate regional assessment of left atrial arrhythmia substrates.
Application of the LA-SUM for intra-patient comparison of imaging
and electrophysiological datasets is demonstrated.
The LA-SUM also facilitates inter-patient comparisons of regional LA
parameters, as demonstrated for segmental PV force-time integrals
during ablation.
1 Introduction
Left ventricular imaging data has long been visualized and
compared using surface flattening techniques (‘polar’ or
‘bull’s eye’ plots). A wide variety of data input sources have
been used to create such plots, including echo strain mapping,
SPECT imaging, and cardiac magnetic resonance imaging [
1,
2
]. By resolving different data sources onto a single spatial
domain, direct comparisons between substrate analysis
techniques for the left ventricle become possible [3]. Meanwhile,
left atrial (LA) electrophysiological substrate assessment has
progressed in recent years with voltage mapping, activation
mapping, rotor mapping, complex signal analysis, CT
imaging, and CMR imaging [
4
], all providing valuable information
in various settings. To deal with such an abundance of
information, we recently proposed a technique to allow
simultaneous representation of multiple parameters on a single 3D
cardiac chamber model [
5
].
Against this background, surface flattening techniques
offer some advantages over 3D shells by (1) enabling
simultaneous visualization of all available information and (2)
facilitating intra- and inter-subject comparisons of datasets. For
example, unfold maps have been used to compare pre- and
post-ablation maps of the same subject [
6
]. Since the shape of
these unfold maps changes with the geometry of the left
atrium, this approach is limited to intra- rather than inter-patient
comparisons. Therefore, in this study, we generate a
standardized regional unfold map (LA-SUM) that follows the same
template for all subjects. Akin to the ventricular ‘bull’s eye’
plot, the proposed LA-SUM allows for intra-patient
comparison of multimodal data and provides a common reference
space for inter-subject analysis. After developing the
LA-SUM, we demonstrate its application in representing
post-ablation atrial enhancement on CMR imaging, and
comparing ablation parameters between cases undergoing
pulmonary vein isolation.
2 Methods
2.1 Study population and data collection
The study population comprised 28 patients who underwent
clinically indicated electroanatomic mapping procedures.
Data collection was approved by the National Research
Ethics Service (REC reference numbers: 10/H0802/77 and
08/H0802/68), and all patients gave written informed consent.
The cases were divided into two sets (see Fig. 1a, b) as
follows:
Set A was used to develop the LA-SUM technique,
including the determination of 2D LA-SUM correlates of
3D LA regions. Set A consisted of 18 patients
(61 ± 12 years, 9 males, 13 paroxysmal AF, 3 persistent
AF, 2 left-sided accessory pathways) undergoing left
atrial local activation time (LAT) mapping prior to
pulmonary vein isolation or accessory pathway ablation.
Set B was used to test the application of the LA-SUM
technique, including intra-patient comparison of
post-ablation scar formation. Set B consisted of ten
patients (60 ± 11 years, seven males, five persistent AF)
undergoing wide area circumferential ablation (WACA)
for pulmonary vein is (...truncated)