Abstract:

Atrial fibrillation (AFib) is the most common sustained arrhythmia in western societies. As a result of structural and electrical variations in the left atrium, pulmonary vein isolation (PVI) has been shown to be effective in treating paroxysmal AFib, but ineffective in persistent AFib. In the management of persistent AFib, PVI plus additionally targeting arrhythmogenic substrate has been used. One technique to identify this substrate is to locate areas with bipolar peak to peak amplitudes < 0.5 mV . Typically, the voltage mapping is conducted during sinus rhythm (SR) for catheter ablation. The purpose of this work is to identify differences and similarities compared to mapping in AFib. 28 patients were prospectively enrolled and mapped using a LASSOTM catheter (15–20 mm diameter) with 20 electrodes (electrode size: 1 mm; spacing: 2-6-2 mm). Voltage mapping with high density (above 800 points) was performed with the CARTO® 3 mapping system both in SR and AFib. Voltage values were provided by the CARTO® 3 system by taking the peak-to-peak amplitude of one beat in the 2.5 second signal (hereinafter referred to as the CARTO value). The average percentage of reliable peaks obtained in the Electrograms (EGMs) was 64.95% in the AFib, slightly higher than in the SR (62.84%). By comparing the CARTO value with the calculated median and average values of reliable peak voltages, the CARTO value matches them on average 66.91% of the time in SR, but only up to 28.87% in AFib. If less than 0.5 mV is assumed to be the ground truth for identifying low voltage areas (LVAs) in SR, less than 0.22 mV was found to be the optimal threshold for LVAs identification in AFib. Using this threshold value the average accuracy value across all patients was 68.68%, with a maximum accuracy of 90.82% in some patients. Similarly, in AFib, a CFAEMean value of less than 80 ms is a standard for identifying a bipolar EGM as a continuous complex fractionated atrial electrogram (CFAE). By comparison this to the duration in SR, greater than 62ms was found to be the best threshold for identifying non-discrete EGM. However, the match is not very good, with the average accuracy across all patients being only 54.93%. When mapping in AFib, the signals can be noisy, therefore, each detected peak can’t be treated as reliable, the reliability calculation can be used to find out the reliable peaks. Although the signal in AFib is noisy, it is possible that contains more information, mapping in AFib should not be ignored. In SR, the CARTO value can represent the whole 2.5s signal well. However, in AFib it does not perform as good as in SR. Voltage mapping in AFib for targeting LVAs should be considered. In addition to prolonged duration, deflection, amplitude, fractionation occupying ratio, etc. should be compared to continuous CFAE in AFib to identify if a better marker in SR can be found to detect these areas.