Analysis of ballistocardiograms using a small scientific digital computer is described. Two steps in processing the body accelerations and concurrent carotid pulses are employed. Desired sequences of heartbeats are selected from data recorded on FM analog magnetic tape. These are digitized and stored permanently on Lint digital magnetic tape. A "scrolledit" program is then employed to identify all heartbeats to be analyzed. This program utilizes a cathode ray storage display unit for visual identification of each heartbeat, and teletypewriter controlled salvage of beginning and ending epochs. The digital tape generated by this procedure is analyzed by the record reading algorithm in the next step. This program works from the carotid pulse data with detection of the anacrotic limb from smoothed first differences at five millisecond intervals. Timing of the ballistocardiographic waves and measurement of their amplitudes is effected by detection of local maxima and minima of smoothed and leveled heartbeats. Correlations of wave shapes of subdivisions of the cardiac cycle are made with those from an ideally normal heartbeat. Summary calculations of each sequence of waves give average waveform and variability in a variety of printer and plotter options.
* Aided by USPHS Grants HE 13060 and GM 15898.