Comparing power spectral density of the 64-channel surface ECG with left atrial electrograms in patients in atrial fibrillation

Study of the mechanisms behind AF is typically based on invasive recording techniques. From a clinical point of view, it is highly desirable to have an alternative, noninvasive characterization of AF. Our aim was to investigate if the left atrium (LA) electrical activity can be seen preferentially in different sites on the surface ECG. Surface recordings of the ECG with 64 electrodes were obtained from 14 patients in atrial fibrillation (AF). After subtracting ventricular activity (QRST), power spectral density (PSD) of atrial activity was calculated using the Welch periodogram, sliding Hamming window (50% overlap). The dominant frequency (DF) was measured from the PSD in the frequency band of 4-8 Hz for each of the 64 channel surface ECGs. Recordings from the LA were obtained simultaneously from a pulmonary vein ablation catheter (PVAC). The DF of atrial activation was calculated from the PSD of the PVAC electrode number 3 (PVAC3) in the same manner as the surface ECG. Baseline recordings of 2 minute duration were analysed. DF differences were calculated between each 64 channels surface ECG and PVAC3. The Pearson´s linear correlation was computed for PSD of each 64 channel surface ECG and PVAC3. The statistical difference between PSD of 32 front and 32 back channels surface ECG and PVAC3 was analyzed for both correlation and DF difference using the paired t-test. There was a highly significant difference between surface ECG and PVAC3 (p=0.00).