An algorithm to estimate the transient ST segment level during 24-hour ambulatory monitoring

An algorithm to estimate the transient ST segment level and to construct the ST segment-level functions from 24-hour ambulatory ECG records is presented. The algorithm was developed and tested using the Long-Term ST Database (LTST DB). Initially, the average heart beats are constructed from normal and non-noisy heart beats of the records of the database in a 16-second neighborhood of each heart beat. Then positions of the isoelectric reference point and the J point are located in each average heart beat. The ST segment-level functions are derived for each ECG lead as a difference in the amplitudes at the point of measurement of the ST segment level (80 ms after the J point) and at the isoelectric reference point. The aggregate average error between the amplitudes of the samples of the ST segment-level functions for all 86 records of the LTST DB, of the total duration of 1991:50:49 [h:min:sec], constructed automatically and those constructed using manually determined positions of the isoelectric reference points and J points was only 0.69 μV (st. dev. 8.89 μV). The ST segment-level functions derived contained no significant artifacts.