Analysis of in:silico Body Surface P:wave Integral Maps show important differences depending on the connections between Coronary Sinus and Left Atrium

Abstract

The electrical connections between the atrial coronary sinus (CS) IntroductionBody surface potential mapping (BSPM) systems offer non-invasive ways to explore the behaviour of the atria. However, it is still very difficult to determine the specific location of ectopic foci when disturbances appear on the recorded signals by only analysing the BSPM. Instead, some experimental studies [1,2] have built and exploited a database of clinical patterns obtained from patients who underwent paced mapping before a diagnostic electrophysiological study. These patterns correspond to body surface P-wave integral maps (BSPiM) where ectopic beats are paced in different atrial sites, and are used to infer how the atria is really activating and how its electrical contribution is observed on the torso surface. This indicator is well correlated with P-wave polarity and amplitude and more importantly, it is robust against fast polarity changes and interpatient variability. To be able to get insight into those clinical studies, biophysical models can be used to analyse the relationship between ectopic atrial activity and BSPiM. However, it requires a very accurate atrial model capable of reproducing existing clinical measurements. This atrial model must include all the anatomical regions to allow the electrical wavefront propagates following muscular connections.In this respect, several clinical studies of the human atria have histologically shown the existence of striated myocardial muscle at discrete locations along the sleeve of the coronary sinus (CS) that electrically connects CS and the left atrial (LA) myocardium [3,4]. The anatomy of these interatrial connections and their location have been previously shown as having high variability between patients. This leads to strong differences in the pathway followed by the atrial depolarization wavefront [3] and influences the BSPiM.Up to now, there is no consensus on the number and location of these muscular connections so 3D computational models of the human atrial anatomy and electrophysiology have not historically included the CS and its bridges to LA as an essential region responsible for the depolarization atrial pattern [5][6][7][8]. However, the influence of these bridges on the depolarization wavefront were partly taken into account in the multi-scale 3D human atrial-torso models previously developed by our group [9,10].The present study combines our most recent multi-scale 3D human atrial-torso model [9] with the analysis of BSPiMs with the aim of determining which configuration of the CS-LA connections reproduces more accurately the set of clinically observed body surface P-wave integral maps (BSPiM). 2.Material and methods Anatomical multi-scale modelOur 3D human atrial model consists of a computational finite element mesh with a homogeneous wall thickness between 600 and 900 μm (754.893 nodes and 515.005 elements), built with linear hexahedral elements and with

Non-invasive localization of atrial ectopic beats by using simulated body surface P-wave integral maps

“…However, when these junctions are activated, both atria depolarized upwards. The BSPiMs computed with this last configuration [ 24 , 38 , 39 ] are very much alike the experimental ones by Sippensgroenewegen [ 10 , 11 ] and helped us to validate the model.…”

“…Thus, when the wavefront first arrives to the RA through the BB and FO (L4, L9 and L14), the simulated BSPiMs are positively signed on the medium and lower torso. However, when the wavefront enters the RA through the CS (L1 and more visibly in L10) the BSPiM changes [ 24 ] and mainly shows positive values on the frontal torso. Similar patterns and location of the maxima and minima values are again observed experimentally (see Fig 4C , lower row), except in the case of L1 where the most negative value produced by our simulation is shifted from the frontal to the rear side on the torso model.…”

“…For instance, they fully determine the pathway followed by the depolarization wavefront when an ectopic focus is localized in the low LA. Proof thereof is the fact that when the bridges are blocked, the wavefront enters the RA through the BB and FO depolarizing the LA upwards and the RA downwards affecting the morphology of the P-wave and therefore altering the BSPiM [ 24 ]. However, when these junctions are activated, both atria depolarized upwards.…”

“…In this work, we have enhanced this previous detailed multiscale atria-torso model [ 23 ] to incorporate more realistic electrophysiology properties at cellular and tissue level [ 24 , 25 ] and to improve the interpolation between scales. The anatomical atrial domain consists of a 3D mesh with 754.893 nodes and 515.005 linear hexahedral elements, and a regular spatial resolution of 300 μm.…”

“…An important improvement has been carried out in the bridges between the Coronary Sinus (CS) and the LA since clinical and histological studies have shown the relevance of the striated myocardial muscles along its sleeve, connecting CS with the LA myocardium [ 38 , 39 ]. In that sense, the longitudinal conductivity on the first two proximal bridges (0,0060 S / cm ∙ pF ) has been increased 7,5 times with respect to the four distal junctions (0,0008 S / cm ∙ pF ) to allow the wavefront to run through these connections and reproduce a more realistic CS-LA wavefront propagation [ 24 ].…”