Non-linear analyses of heart rate dynamics reveal subtle changes not evident from conventional heart rate variability measures. Traditionally, the information was inferred from 24-hour ECG recordings, making it less suitable for clinical application. Moreover, only few studies have attempted to evaluate the reliability of non-linear analyses in relation to varying proportion of artifacts in tracings. In 67 patients revascularized with beating-heart technique, fractal dimension and detrended fluctuation analyses were obtained from 24-hour Holter and 15-minute high-resolution ECG recordings pre and postoperatively. We found strong correlations of non-linear indices between 24-hour and 15-minute recordings (0.54-0.77, p<0.001), unaffected by proportion of artifacts.