Power spectral analysis of finger plethysmographic waveform in patients with coronary artery disease and after coronary artery bypass graft surgery

Background: The aim of the present study was to assess the clinical significance of spectral analysis of plethysmographic waveform in patients with coronary artery disease (CAD) and after coronary artery bypass graft (CABG) surgery. Methods and Results: The study group comprised 26 healthy subjects, 15 CAD patients, and 24 CAD patients after CABG. Finger plethysmographic waveforms from both right and left index fingers were recorded and analyzed using power spectral analysis. The total power of the right pulse was found to be higher than that of left pulse in the 3 groups of subjects. In CABG patients, the total power of both pulses was increased, the right-to-left ratio of bilateral total power was decreased, and the power of the harmonics of the right pulse shifted from high-frequency to low-frequency. The normalized power of the 4th harmonic of the left pulse and of the 3rd and 4th harmonics of right pulse decreased, whereas that of the 1st harmonic of right pulse increased in CABG patients. Several harmonics correlated significantly to some heart rate variability measures in both controls and CAD patients, but not in CABG patients. Conclusions: The increase in the total power of both pulses, the shift of the normalized power of harmonics of the right pulse from high- to low-frequency, and the decrease in the right-to-left ratio of the total power of both pulses are the 3 significant changes in the power spectra of the pulses in CAD patients after CABG. The plethysmographic waveform of normal controls and CAD patients may be modulated by the autonomic nervous system, and in CAD patients the CABG surgery may have diminished the effect of autonomic nervous modulation on the pulse waveforms.