Module title = Tutorial: ACS Plus

Lesson title = The ST Segment

• absolute position: elevation vs. depression
• slope: upsloping vs. downsloping vs. none
• shape: flat vs. concave vs. convex 

In the previous lesson on J point, we have described J point elevation and depression. ST segment absolute position (elevation and depression) is the same concept. Here is an example of ST segment elevation:


In the above example, can you see that the J point is more that 3 little red squares above the baseline, which is 0.3 mV. The blue dotted line shows the baseline and the red dotted line indicates the starting elevation of the ST segment:


Here is an example of ST segment depression:


The blue line is the baseline and the red line indicates the degree of ST depression. The ST depression is 2 little squares in this example, which is 0.2 mV:


After you analyze the elevation or depression of the ST segment, next analyze the slope of the ST segment. It be: upsloping, downsloping, or have no slope.

This ECG has an upsloping ST segment. The blue dotted line is the zero degrees baseline. The red dotted line is parallel with the ST segment and is angled/sloped upwards:

The above example also shows ST segment elevation. Do not confuse absolute position with sloping. The above example has ST segment elevation that is upsloping.

Here is an example of ST depression with downsloping:



Here is an example of ST depression with no sloping:



Lastly, analyze the shape of the ST segment. It can be flat, concave, or convex. The concave shape is sometimes also called "scooped".

This ECG shows a diffuse J point with ST segment elevation that is concave upward:


The blue line travels from the J point (approximately) to the peak of the T wave. The red arrow indicates the space under the blue line to show the ST segment is concave upward.


The opposite of concave up is convex up. Here is an example of convex up, where the ST segment is above the blue line that connects the J point and the top of the T wave. The red arrow shows the space between the ST segment and the blue line:


The ST segment can also be concave down which can occur with ST depression. Note that the T wave in this example is downgoing and contributes to the overall shape of the ST segment. The blue line connects the J point and the tip of the T wave and the red arrow shows the space between the blue line and the ST segment.


Compare now with examples of flat ST segments. This ECG has ST elevation that is upsloping and flat:


This ECG has ST depression, has no slope and is flat:


This ECG has ST depression, is downsloping and is flat:


Summary:

Analysis of the ST segment must include the 3 details:

• absolute position: elevation vs. depression
• slope: upsloping vs. downsloping vs. none
• shape: flat vs. concave vs. convex