Fig. 2. Examples of power-law slopes (top ) before (left ) and after (right ) CABG, power spectral analyses (middle ), and the short-term correlation property (α¹) (bottom ) before (left ) and after (right ) coronary artery bypass graft in the same patient. The postoperative power spectra show no respiratory peaks, and the scaling exponent α¹shows completely random heart rate dynamics postoperatively. In the figure of scaling exponent α¹(bottom ), the x-axis represents the log of window size (n) ≤ 11 beats. The y-axis represents the average root mean square fluctuation of integrated and detrended time series as a function of window size n. The data was analyzed from 24-h epochs.