An algorithm to estimate the ST segment level in 24-hour ambulatory ECG records

We present an algorithm to estimate the ST segment level, and to construct the ST segment level function. The algorithm was developed and tested using the Long-Term ST Database (LTST DB). The algorithm determines the positions of the isoelectric level and the J point in average heart beats constructed from 16-second windows of normal and non-noisy heart beats. Then the samples of the ST segment level function are derived for each ECG lead. The aggregate average error between the amplitudes of the samples of the ST segment level functions, for 190 ECG leads of the LTST DB, constructed automatically and those constructed on the basis of manually set positions of the isoelectric level and the J point by the human expert annotators of the database was 0.69 muV (std. 8.89 muV).