DESCRIPTION OF THE LTST DATABASE ANNOTATION FILES Here is updated description of the annotation files and ST annotation codes (and related measurements) according to the annotation protocol used for the records of the LTST DB. Each record in the LTST database includes the following files: (The format of the files is the MIT DB format.) sXXXXX.dat Data file (Two channel ECG data sampled at 250 Hz.) sXXXXX.hea Header file sXXXXX.ari ARISTOTLE's file (QRS labels attached to each heart beat, plus rhythm changes.) sXXXXX.atr Atruth file (QRS labels as manually determined attached to each heart beat, plus rhythm changes.) sXXXXX.sta ST annotation atruth file (This is the ST ANNOTATION file.) sXXXXX.16a ST measurement atruth file (The ST measurements were derived from the AVERAGE heart beats. These average heart beats are composed for each single heart beat (those which passed the preprocessing phase as clean) from the 16 second time window surounding each heart beat. The ST measurements thus obtained are attached back to single heart beats.) XXXXX - the record number 1. sXXXXX.16a file: (What it contains): First, we computed average heart beats in the time windows of 16 seconds for each clean heart beat. Clean heart beats are those which passed filtering in the KL space during preprocesing phase. After that, we manually set the position of the point defining the isoelectric level and J-point for these average heart beats. Not for all of them, but very frequently, i.e., prior to ST episode, at the peak of ST episode, after the ST episode, prior to axis shift, after the axis shift, otherwise approximately every 20 minutes. This manual seting of the two fiducial points is performed during dummy annotation phase. The positions of the points defining the isoelectric level and J-points for the rest of average beats were computed using linear interpolation. After that, we computed a number of ST measurements for each average beat. These ST measurements were attached back to each single heart beat. So, each ST annotation in the file sXXXXX.16a is attached to a heart beat and contains ST measurements obtained on the corresponding average heart beat. Noisy heart beats are not attached with these annotations. They were judged as noisy during the preprocessing phase. Time index of each ST annotation: ARISTOTLEs fiducial point plus 16 mili seconds. The format of ST annotation is: [DMY]STx+-aaaa,+-aaaa,+-aaaa,+-aaaa,+-aaaa,+-aaaa, (a) (b) (c) (d) (e) (f) +-aaaa,+-aaaa,NNint,Jpoint,J8060,nleft,nright (g) (h) (i) (j) (k) (l) (m) (a) ST amp.at J+80(60)(*) (b) ST amp.at J-point (c) ST amp.at J+20 (d) ST amp.at J+40 (e) ST amp.at J+60 (f) ST amp.at J+80 (g) ST amp.at J+100 (h) ST amp.at J+120 (i) Position of isoelectric level (mili seconds prior to ARISTOTLE's fiducial point) (j) Position of J-point (mili seconds after the ARISTOTLE's fiducial point) (k) Position of the point of measurement (mili seconds after the ARISTOTLE's fiducial point) (l) Number of heart beats left of current heart beat included into the average beat (m) Number of heart beats right of current heart beat included into the average beat (**) (The ST amplitude measurements (isoelectric level, J+XX ms) were obtained as means of five ECG samples (20 mili seconds) in the average waveforms.) x: Lead number [DMY]: Whether or not the average beat corresponds with manually obtained measurements (none: Does not, the measurements were obtained according to prior interpolation of the positions of the points defining the isoelectric level and J-points DMY: The average beat corresponds to manually determined measurements. The positions of the point defining the isoelectric level and J-point were determined manually for this average heart beat.) (*) These measurments were obtained at the J-point plus 80 (or 60ms). The point of measurement was determined according to heart rate by the following rule: J+80 if HR < 100 bpm J+72 if HR >= 100 bpm and HR < 110 bpm J+64 if HR >= 110 bpm and HR < 120 bpm J+60 if HR >= 120 bpm These measurements (J+80(60)) also serve as a basis for the ST LEVEL FUNCTION which was used for ST annotating regarding ST episodes. These ST annotations are described below in item 2. (**) Thus, nleft + nright + 1 equals total number of heart beats included into this average. 2. sXXXXX.sta file (What it contains): ST annotations in this file mark: global reference, local reference, the beginning of an ST episode, its extrema, its end, noise, axis shift, or change due to QRS conduction change. The ST measurements, i.e., ST amplitudes at J+80(60) obtained on average heart beats are the basis for the raw ST LEVEL FUNCTION. The J+80(60) samples were then smoothed, resampled (0.5 Hz) and smoothed (7 point moving average - window of 12 seconds) thus forming smooth ST LEVEL FUNCTION (or just ST LEVEL FUNCTION). Next, we set a global reference and many local reference annotations in the ST LEVEL FUNCTION for each ECG lead throughout the record. By inserting the local references we tracked the ST REFERENCE FUNCTION of the ST segment level (reference ST level). After that, we subtracted the ST REFERENCE FUNCTION (piecewisely linearly approximated ST LEVEL FUNCTION from local reference to local reference) from the ST LEVEL FUNCTION. Thus, we ended in the ST DEVIATION FUNCTION (or subtracted function). Next, we annotated ISCHEMIC and RATE-RELATED episodes in the ST DEVIATION FUNCTION. We also annotated noises and unreadable intervals. Previously, during tracking the ST REFERENCE FUNCTIN, we annotated axis shifts and shifts due to QRS conduction changes. Description of annotation codes: Time index: Index of sample in the ST DEVIATION FUNCTION. ST annotation codes: The annotations could be in lower or in upper case characters. Upper case: Annotations were set with regard to global reference in the ST LEVEL FUNCTION. (These annotations are global reference and local references.) Lower case: Annotations were set with regard to the ST REFERENCE FUNCTION (reference ST level) in the ST DEVIATION FUNCTION. (These are annotations for ischemic episodes, rate-related episodes, axis shifts, conduction change shifts, noises and unreadable events.) Code Meaning GRST x Global reference LRST x +- llll Local reference s[cc]st x Significant ST shift ([rt]st x +- dddd Beginning of significant ST episode a[rt]st x +- dddd Extrema of significant ST episode [rt]st x +- dddd) End of significant ST episode noi x +- dddd Noise (und x Beginning of unreadable interval und x ) Beginning of unreadable interval Legend: x: lead number (0 or 1 or 2) +- llll: ST level in microV +- dddd: ST deviation in microV [cc]: type of ST shift (none: axis shift cc: conduction change) [rt]: type of episode (none: ischemic rt: rate-related) Critera for episodes: 1.An episode begins when the magnitude of the ST deviation function first exceeds 50 uV; 2.The deviation must reach a magnitude of Vmin or more throughout a continuous interval of at least Tmin; 3.The episode ends when the deviation becomes smaller than 50 uV, provided that it does not exceed 50 uV in the following 30 seconds. 3. sXXXXX.stb file Vmin = 100 uV, Tmin = 30 s 4. sXXXXX.stc file Vmin = 100 uV, Tmin = 60 s ------------------------------------------------------------------------------------------