ST-SEGMENT Trending Capabilities

  • 2009 Mar 1

Because of the dynamic nature of acute coronary syndromes, when STEMI is suspected but the initial ECG is non-diagnostic, EDs are generally required to either manually obtain a 12-lead ECG every five to 10 minutes or use an ST-segment monitor to trend the ST segment (a Class I recommendation). 

At least one prehospital monitor offers a feature known as "ST segment trending," which emulates the function of an ST-segment monitor. In units with ST trending, once the "12-lead" button is pressed, the device not only samples and prints a 12-lead ECG but will then automatically re-sample a 12-lead every 30 seconds thereafter. This re-sampling is done internally, and the 12-lead is not printed out or displayed on the screen.

The monitor analyzes the re-sampled ECGs and identifies changes of at least 1 mm in the ST segment, whether upward or downward. Such a change in one sample may be due to an ischemic event or may simply be the result of patient movement or artifact. Therefore, the ST-segment trending algorithm requires the change to persist for five samples, or about two and a half minutes, before meeting the threshold for an alert.

If the ST segment change meets that threshold, a new 12-lead is printed, alerting the care provider and documenting the event. The ECGs in Figure 1 captured the STEMI by use of this feature.

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