A COMPUTER ALGORITHM TO IMPUTE INTERRUPTED HEART-RATE DATA FOR THE SPECTRAL-ANALYSIS OF HEART-RATE-VARIABILITY - THE ARIC STUDY

The shorter term beat-to-beat heart rate data collected from the gener al population are often interrupted by artifacts, and an arbitrary exc lusion of such individuals from analysis may significantly reduce the sample size and/or introduce selection bias. A computer algorithm was developed to label as artifacts any data points outside the upper and lower limits generated by a 5-beat moving average +/- 25% (or set manu ally by an operator using a mouse) and to impute beat-to-beat heart ra te throughout an artifact period to preserve the timing relationships of the adjacent, uncorrupted heart rate data. The algorithm applies Fa st Fourier Transformation to the smoothed data to estimate low-frequen cy (LF; 0.025-0.15 Hz) and high-frequency (HF; 0.16-0.35 Hz) spectral powers and the HF/LF ratio as conventional indices of sympathetic, vag al, and vagal-sympathetic balance components, respectively, We applied this algorithm to resting, supine, 2-min beat-to-beat heart rate data collected in the population-based Atherosclerosis Risk in Communities study to assess the performance (success rate) of the algorithm (N = 526) and the inter- and intra-data-operator repeatability of using thi s computer algorithm (N = 108). Eighty-eight percent (88%) of the reco rds could be smoothed by the computer-generated limits, an additional 4.8% by manually set limits, and 7.4% of the data could not be process ed due to a large number of artifacts in the beginning or the end of t he records. For the repeatability study, 108 records were selected at random, and two trained data operators applied this algorithm to the s ame records twice within a 6-month interval of each process (blinded t o each other's results and their own prior results). The inter-data-op erator reliability coefficients were 0.86, 0.92, and 0.90 for the HF, LF, and HF/LF components, respectively, The average intra-data-operato r reliability coefficients were 0.99, 0.99, and 0.98 for the HF, LF, a nd HF/LF components, respectively. These results indicate that this co mputer algorithm is efficient and highly repeatable in processing shor t-term beat-to-beat heart rate data collected from the general populat ion, given that the data operators are trained according to standardiz ed protocol. (C) 1996 Academic Press, Inc.