Detection of Endo-epicardial Asynchrony in the Atrial Wall Using One-Sided Unipolar and Bipolar Electrograms

Figures

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  Unipolar electrograms are more suited than bipolar electrograms to detect endo-epicardial asynchrony on one side of the atrial wall using electrogram fractionation.

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  Fig. 1. Simultaneous endo-epicardial mapping in patients during cardiac surgery. a The mapping tool consists of two identical electrode arrays fixed to each other. One leg (electrode array) of the mapping tool is introduced in the right atrium via a standard surgical incision for cardio-pulmonary bypass. This allows to record electrograms from the epicardium (outside wall) and endocardium (inside wall) simultaneously. b The properties of the electrode array. c Mapping locations at the right atrium. d Examples of directly opposite epicardial (epi) and endocardial (endo) unipolar electrograms. Endo-epicardial atrial activation (A) is in synchrony in the first two beats, the following atrial extrasystole demonstrates asynchronous endo-epicardial atrial activation. V, ventricular activation; LAT, local activation time. e Example of atrial asynchrony and additional deflections next to the LAT deflection on unipolar electrograms (=fractionation). One fractionation-deflection on each electrogram corresponds to the asynchronous activation on the opposite side

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  Fig. 2. Data selection and analysis. Top left: epi- and endocardial activation maps constructed from unipolar electrograms acquired from simultaneous endo-epicardial mapping. Top right: endo-epicardial activation maps constructed after subtracting unipolar electrograms in the horizontal (X) direction creating bipolar electrograms. Crosses indicate electrogram sites with endo-epicardial asynchrony (EEA) that are included for the study. Red circles represent a broken electrode site and endo-epicardial electrograms at this site are excluded from the study. Bottom: unipolar and bipolar epi- and endocardial electrograms from the site marked with the white cross. Local activation time is marked at the steepest slope for unipolar electrograms and at the largest peak for bipolar electrograms (red crosses). Fractionation time (FT) is determined by marking the steepest slope of additional deflections for unipolar electrograms and by marking additional peaks for bipolar electrograms (blue markers). If the difference between a FT and the local activation time of the opposite electrogram is ≤7ms, 4ms in the unipolar electrogram example and 3ms in the bipolar (Y) electrogram example, this…

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  Fig. 3. Presence of EEA corresponding fractionation on unipolar and bipolar electrograms. Boxplots of the percentage of electrode sites with EEA where the electrogram shows fractionation corresponding to EEA for observer 1 (top) and observer 2 (bottom). Outliers (>1.5 interquartile range) are presented as asterisks

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  Fig. 4. Unipolar versus bipolar electrograms. a Two electrogram examples demonstrating decrease of signal-to-noise ratio of fractionation corresponding to EEA (SNRcorr) in bipolar endocardial electrograms in the y-direction. Blue arrow points to fractionation on the endocardial electrogram corresponding to the primary deflection/peak of the local activation time on the epicardial electrogram. b Two electrogram examples demonstrating increase of additional fractionation (Fadd) on the bipolar endocardial electrogram in the x-direction. Red cross indicates local activation time. Blue crosses or circles indicate fractionation. Blue arrows indicate fractionation which (1) does not correspond to EEA, (2) not within noise level of the baseline, and (3) is ≥15ms removed from the local activation time (= Fadd)

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  Fig. 5. Peaks in bipolar electrograms Top left: a bipolar electrogram from two similar shaped signals with only one moved 1 sample on the time (x-)axis is the same as the derivative (∆) of the signal. The minimum of the derivative is the steepest negative slope of the original signal. Top right: if the positive and negative poles are switched, the bipolar electrogram is the negative derivate (−∆). The maximum of the bipolar electrogram is in this case the steepest negative slope of the signal. Bottom: three examples of fractionated unipolar electrograms where the two unipolar electrograms switch in which is de leading electrogram between the different fractionated components. For example, for the electrograms on the left, the light grey unipolar electrogram deflects negatively before the dark unipolar electrogram. The bipolar electrogram shows a positive peak at this point. However, with the following deflection, the dark unipolar electrogram deflects before the lighter unipolar electrogram deflects. Here, the bipolar electrogram shows a negative peak. Therefore, it is not possible in these bipolar electrograms to determine if a peak is a unipolar negative deflection (voltage decrease)…