Monitoring ST Segments

To monitor ST analysis, take the following steps.

    1. Identify with the physician the lead(s) that you wish to monitor. Usually two leads monitoring either side of the area of suspected ischemia is selected to monitor for extension. If using a V lead, ensure that the electrode is correctly placed.

    2. Perform a proper skin prep. Reapply all electrodes as follows prior to starting ST analysis.

    3. Clip Hair; avoid shaving area as the removal of epithelium may cause an inflammatory response on skin surface that can diminish quality of transmission. .

    4. Roughen Skin

    Roughen skin at each site until red by rubbing with the sandpaper circle attached to each red dot.

    5. Attach

    Attach cables to Red Dot before application of Red Dot to skin. If you press the Red Dot on, you squeeze the conducting gel out and diminish efficiency. (It is also more comfortable for the patient to connect before application).

    6. Ensure that you have an ECG with ST analysis capabilities. ST will flash in the upper right corner beside the ECG waveform. You will not be able to enter the ST program until monitoring of ST has been in place for at least a minute (processing of data). If a flashing "?" appears beside the ST display, you will not be able to enter the ST program until a number appears. Once a number appears under ST, you can access ST mode through the ECG review.

P point: locate on isoelectric line between P and QRS.ST is the distance above (+) or below (-) the isoelectric line (using P point as reference). J Point: locate at end of QRS.The distance selected (e.g. .60 or .80 seconds) is measured from the J Point. This is the point where ST height or depth is measured. 4. Select "ECG"

      Select "more"

      Select "review"

      Select "change points"

    A picture of the patient's ECG will appear. With some modules, it will be greatly magnified. Three dots will be displayed on the ECG. The first is the PR point, the second the J point and the third shows the point where ST is measured.

    Point 1 - The PR point

    The PR point should be positioned in the PR interval but on the isoelectric line. It should not be on the P wave or wave slope. The PR point references the monitor to the horizontal axis. The ST measurement displayed is the height of the waveform above or below the isoelectric line.

    Point 2 - The J point

    The joint point by definition is the end of the QRS. The ST segment begins from the J point.

    Point 3 - The ST analysis point

    This point shows exactly where the ST segment is measured. The value displayed is the distance that the ST segment is above or below the isoelectric line (referenced by the PR point) at the ST analysis point.

    7. Setting the points

    PR Point

    If the PR point is not on the isoelectric line, you need to manually set it. To do so, once in the "change points":

    Select "manual"

    Select "PR"

    Move cursor until point is located where you want it

    Select "enter"

    J Point

    If the J point if not the end of the QRS, you may set it as above only select "J".

    ST analysis point

    The monitor will automatically select 60 ms for the ST measurement point. This means that ST height above the isoelectric line will always be measured from exactly 60 ms (11/2 small boxes) to the right of the J point. You cannot move the ST analysis point in isolation. It automatically moves (staying 60 ms to the right) when the J point is moved. You may choose to have ST analysis at 80 ms if you wish.

    Confirm all changes by selecting enter.

    8. Adjust alarms.

    Alarms automatically are set to ring if ST goes up or down by more than 1.00 mv. You may adjust alarms by:

    Select "ECG"

    Select "Alarm"

    Select "ST"

    9. Monitor trends.

    Once you have set the points for measurement, do not keep adjusting. The most important point in ST analysis is to monitor trends - monitor for changes in ST height when measured exactly the same way.

    You may print a strip by entering "ECG - More" and selecting print. You will only receive a print-out of the last 30 minutes. Six complexes each 5 minutes apart will be printed. Five minutes later, the most recent complex is added and the oldest dropped.

    10. Record ST hourly on flow sheet

    Record ST segment hourly on flow sheet recording both lead and ST height.

    11. Record a print out of trends q 12 h.

    A trend record showing the numerical value of the ST height should be posted in the ECG strip section q12h to document changes. Identify on the record dramatic changes that occur because the points were changed.

    To obtain a trend print out:

    Select "ECG"

    Select "More"

    Select "Review"

    Select "Trends"

    Select "Print"

LHSCHealth Professionals

Last Updated March 24, 2009 | © 2007, LHSC, London Ontario Canada