Background: Voltage based recording of intracardiac potentials have been the mainstay of electrophysiological studies but have limited spatial resolution owing to far-field interference. The electric fields measured by voltage recordings are created by localized differences in membrane charge and therefore direct measurement of Charge Density may reduce far-field effects. Previous investigations of AF using voltage recordings have demonstrated an overall Dominant Frequency (DF) driving this seemingly unstable rhythm.
Objective: To assess whether using Charge Density recordings for analysis of DF provides additional information compared to voltage.
Methods: Unipolar, non-contact, endocardial recordings of Charge Density and voltage were concomitantly collected from 28 patients in AF undergoing ablation procedures using the Acutus AcQMap system. Individual recordings from >3600 surface potentials were identically pre-processed by filtering, detrending and windowing, then analysed using Fourier transform to calculate spatially specific measures of DF and Regularity Index (RI). Atrial geometry was assessed using intracardiac ultrasound.
Results: Mean DF was significantly greater in Charge Density (10.3±0.4 Hz) compared with voltage (9.3±0.6 Hz, p=0.003) recordings. The smallest DF was similar between both Charge Density and voltage (5.1±0.7 Hz vs. 4.9±0.6 Hz, p=0.77), however the maximum DF was significantly higher in Charge Density recordings (14.3±0.6 vs. 12.9±0.4 Hz, p=0.036). RI was also greater in Charge Density compared with voltage recordings (0.14±0.004 vs. 0.12±0.004, p<0.0001), suggesting a lower degree of variation around the DF. Neither DF nor RI were altered by standard ablation procedures. Mean atrial volume was 166.3±8.0 ml and showed modest correlation with larger surface areas of endocardium with higher DF in Charge Density (R=0.41, p=0.032) but not voltage recordings.
Conclusion: DF is typically higher in Charge Density recordings, owing to an increased detection of higher DF values. This is potentially due to a greater ability to discriminate between regions with higher DF due to an increase in spatial acuity, which may have been masked by far-field contamination in voltage recordings.