Electrocardiographic Signal Broadband Properties

Background: Low, high, and ultra-high-frequency ECGs measure ventricular activation differently. However, their principles and properties have not yet been studied systematically. Method: 5 kHz ECG resting recordings were acquired in 134 subjects. We used an extended 12-lead ECG setup with 6 (V1-V6)+6 extended precordial leads. We measured the distance of all precordial leads to the ventricular geometrical center with the magnetic resonance images. We determined the amplitude of frequency components for each lead by computing the area of the averaged amplitude envelopes during the QRS complex. We used five frequency bands: LF (0.2-20 Hz), MF (20-80 Hz), HF (80-300 Hz), UHF1 (300-500 Hz), and UHF2 (800-1.000 Hz). Results: The relative amplitude decreases with relative distance from the myocardial depolarization source and significantly differs in frequencies. The decay coefficient in the LF band is more than two times lower than the UHF2 band coefficient. All differences between frequencies are significant p<0.005. Conclusion: Lower frequencies are more sensitive to distant areas, and higher frequencies are more sensitive to near regions. Combining multiple frequency bands has the potential to localize activation sources more precisely.