Impact of recording technologies on cardiac electrogram morphology: implications for mapping and interpretation

Figures

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  Fig. 1. Biophysical basis of electrogram formation Schematic illustration of the relationship between activation wavefront propagation and electrogram morphology. Unipolar electrograms represent extracellular potentials recorded relative to a distant reference electrode. At sites of excitation onset, activation propagates away from the recording electrode, resulting in a predominantly negative deflection (S-wave or QS-morphology). When the activation wavefront passes beneath the electrode, a biphasic RS-morphology is recorded. At sites of wavefront termination or conduction block, activation propagates toward the recording electrode, resulting in a predominantly positive deflection (R-wave). Bipolar electrograms are generated by calculating the voltage difference between two adjacent electrodes and therefore reflect local extracellular voltage gradients. Bipolar potential morphology and polarity depend on both activation direction and electrode orientation relative to the propagating wavefront.

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  Fig. 2. Influence of signal-processing techniques on unipolar and bipolar single potential morphology. Representative unipolar single potential (left column), and corresponding horizontal bipolar (middle column) and vertical bipolar (right column) potentials subjected to different signal-processing approaches. Rows illustrate the effects of raw signal acquisition containing noise artifacts, high-pass filtering, low-pass filtering, notch filtering, reduced sampling frequency and optimized signal processing. Signal-processing parameters substantially alter electrogram morphology, potential voltage, duration and high-frequency content. High-pass filtering suppresses low-frequency components and baseline drift, whereas low-pass filtering attenuates high-frequency noise. Notch filtering selectively removes powerline interference but may introduce waveform distortion. Reduced sampling frequency decreases temporal resolution and may impair characterization of potential slope and voltage. The most optimal signal processing is achieved by unipolar band-pass filtering of 0.5-400 Hz and bipolar 20-400 Hz.

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  Fig. 3. Influence of signal-processing techniques on unipolar and bipolar fractionated potential morphology. Representative unipolar fractionated potential (left column), and corresponding horizontal bipolar (middle column) and vertical bipolar (right column) potentials subjected to different signal-processing approaches as in Fig. 2. Signal-processing parameters substantially alter electrogram morphology, potential voltage, duration and high-frequency content. High-pass filtering suppresses low-frequency components and baseline drift, whereas low-pass filtering attenuates high-frequency noise and may reduce apparent fractionation. Notch filtering selectively removes powerline interference but may introduce waveform distortion. Reduced sampling frequency decreases temporal resolution and may impair characterization of potential fractionation, slope and voltage. The most optimal signal processing is achieved by unipolar band-pass filtering of 0.5-400 Hz and bipolar 20-400 Hz.

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  Fig. 4. Comparison of advanced electrogram reconstruction techniques on single potentials. (A) Local electrode configuration used for electrogram reconstruction. The red and green electrode pairs represent the orthogonal bipolar recordings used for omnipolar reconstruction, while the yellow square indicates the location of the reconstructed omnipolar electrogram. The purple electrodes indicate the center electrodes from which multipolar and Laplacian electrograms are reconstructed using information from surrounding neighboring electrodes. (B–D) Corresponding unipolar, horizontal bipolar and vertical bipolar potentials obtained from the selected electrode configuration. (E) Electric-field (E-field) loop reconstructed from the orthogonal bipolar components. The yellow arrow indicates the direction of maximal E-field magnitude, corresponding to the direction of maximal voltage change and local activation direction. (F) Omnipolar electrogram reconstructed along this direction from the orthogonal bipolar recordings. (G) Multipolar potentials derived from multiple neighboring electrodes, with the original unipolar potential shown for comparison. (H) Laplacian potential reconstructed from a…

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  Fig. 5. Comparison of advanced electrogram reconstruction techniques on fractionated potentials. (A) Local electrode configuration used for electrogram reconstruction. The red and green electrode pairs represent the orthogonal bipolar recordings used for omnipolar reconstruction, while the yellow square indicates the location of the reconstructed omnipolar electrogram. The purple electrodes indicate the center electrodes from which multipolar and Laplacian electrograms are reconstructed using information from surrounding neighboring electrodes. (B–D) Corresponding unipolar, horizontal bipolar and vertical bipolar potentials obtained from the selected electrode configuration. (E) Electric-field (E-field) loop reconstructed from the orthogonal bipolar components. The yellow arrow indicates the direction of maximal E-field magnitude, corresponding to the direction of maximal voltage change and local activation direction. (F) Omnipolar electrogram reconstructed along this direction from the orthogonal bipolar recordings. (G) Multipolar potentials derived from multiple neighboring electrodes, with the original unipolar potential shown for comparison. (H) Laplacian potential reconstructed from…

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  Fig. 6. Determinants of electrogram formation and interpretation. Electrogram characteristics arise from the interaction between underlying electrophysiological properties and multiple technological factors. Conduction properties, anisotropy, structural remodeling and activation patterns determine the extracellular potential field. Recorded signals are subsequently influenced by electrode acquisition characteristics, signal-processing methods and electrogram reconstruction techniques, ultimately shaping electrogram representation and clinical interpretation through voltage mapping, activation mapping and substrate characterization. EGM = electrogram.