Systematic differences of non-invasive dominant frequency estimation compared to invasive dominant frequency estimation in atrial fibrillation

Figures

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  Fig. 1. A. Intra-procedural fluoroscopy showing the presence of left atrial (LA) and right atrial (RA) non-contact arrays (white asterisks), Body Surface Mapping (BSM) electrodes (white arrow heads) and ablation catheter (white arrow); B. Overview of BSM setup during atrial fibrillation (AF). Electrodes positions are indicated with black dots. Interpolation was performed using the Surface Laplacian method [28]; C. Example of virtual electrogram data during AF before (top) and after (bottom) QRST subtraction; D. BSM data from the same time window as in C, before (top) and after QRS (bottom) subtraction.

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  Fig. 2. Example of Highest DF (HDF) binning for a hypothetical dataset. For each window, the HDF for the VEGMs is found. VEGM HDF values within a 0.5 Hz range are combined into a single HDF bin. The difference in HDF values between the BSM and VEGM data for all windows within one HDF bin are then collected and their distribution is represented as a boxplot. The median values of these boxplots were used to determine a correlation between VEGM HDFs and BSM HDFs.

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  Fig. 3. Example of a DF window without OI threshold, and when applying an OI threshold of 0.5. A. DF maps for the right and left atrium and body surface. Black dots on the left atrium indicate positions where no HDF could be determined. Black dots on the BSM indicate electrode locations. Colors at locations where no HDF was measured or identified are interpolated using the surface Laplacian for visualization purposes [28]. Areas of HDF on the atrium are indicated (white ellipses); B. VEGM signal and frequency spectrum for an HDF node from the window visualized on the DF maps. C. VEGM signal and frequency spectrum for a HDF node after OI thresholding (OI > 0.5). HDF area and location have both changed in the left atrium.

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  Fig. 4. Effect of increasing the organization index (OI) threshold on the percentage of windows with a defined Highest Dominant Frequency (HDF) (excluding windows identifying harmonics or only HDFs below the OI threshold) for both virtual electrograms (VEGM, left) and body surface maps (BSM, right). Percentages are given as percentage of windows including windows for which a harmonic DF was identified. Black lines indicate the average behavior across all subjects. Grey lines indicate the behavior for individual subjects.

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  Fig. 5. Distribution of the Highest Dominant Frequency (HDF) values on the virtual electrograms (VEGM) and body surface (BSM) for each patient (median, inter-quartile range and range are indicated). Asterisks indicate statistically significant difference (***; p < 0.001, *; p < 0.05). The number of HDF windows per bin is presented above each bin. A. No OI threshold for either group; B, OI threshold >0.5 applied to both groups; C, BSM OI threshold = 0 and VEGM OI threshold >0.5.

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  Fig. 6. Distribution of the differences in Highest Dominant Frequency (HDF) value between body surface (BSM) and virtual electrograms (VEGM) per electrogram HDF bin. Median and spread per 0.5 Hz VEGM interval are indicated, as well as the number of windows within the interval. Parameter estimates and their 95% confidence intervals are given for a best fitting exponential curve based on the average median difference. A. No OI threshold; B; OI threshold >0.5; C. Fitted curve for VEGM OI threshold >0.5 and BSM OI = 0; D. Fitted curve for OI thresholds up to OI = 0.8.

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  Fig. 7. HDF atrial area distribution for VEGM and BSM HDF values with the same (grey) and different (black) HDF values on the body surface when compared against the intra-cardiac signal. HDF values were considered “Same” if the HDF of the body surface was within 0.5 Hz of the VEGM HDF value for a particular window, “Different” if otherwise. Atrial area distributions are shown for OI thresholds of 0 (left) and 0.5 (right). The Y-axis indicates the ratio of windows for which the HDF covers a specific percentage of the atria, normalized to the total number of windows.