In order to address these issues, there are three important questions which must be answered in order to accurately measure the ST segment.
1. Where is the baseline?
2. Where is the J point?
3. Where exactly do we find that J point?
This can be easy when we have a flatter ST segment as in Fig 1.
It is more difficult with a sloping ST segment as in Fig 2. When the position of the J point is not clear cut it will make the measurement of the height of the ST segment also more variable. Possible sites (see variability points) which may be used to measure this ST segment can be seen [5].
Fig 3: ST segment displayed with variability points (click on the ECG to enlarge)