TERMINAL QRS DISTORTION
In this section, we will compare four tracings
Please refer to the ECG below as an example of a Classic Normal ECG. Let us focus on the terminal portion of the QRS complexes. Specifically, I want you to note the following:
- The right-most precordial leads V1, V2, V3 take on an rS configuration (r << S)
- The left-most precordial leads V4, V5, V6 take on a qR configuration (q << R)
Sometimes during the evolution of the acute Anterior STEMI, you will see the terminal S-wave begin to rise toward the baseline. When the terminal S-wave rises above the baseline then it technically is no longer an S-wave. When this occurs it is described as “terminal QRS distortion”. This is highly suspicious of the Acute STEMI(this holds especially true of Leads V2, V3).
NOTE : An exception to this rule occurs when the take off of the J-point forms the shape of a “fish hook” (J-wave)—–if this J-wave is present, the probability shifts in the direction of a benign normal variant.
The rising of the nadir of the S-wave is demonstrated in the Illustration below:
Similarly if the QRS complex takes on a qR configuration, you might observe the following phenomena. As the acute STEMI evolves, the J-point take off will rise with time. When the J-point rises to > 50% the R-wave height it is called “terminal QRS distortion”.
This is highly suspicious of the acute STEMI(this holds especially true of Leads V5,V6)(the exception again occurs if a J-wave is present). This rising of the J-point is shown schematically in the Illustration below.
We will now compare four tracings using the following chart (see below chart for ECG Tracings).
Tracing #1.a Hour “0”
Tracing #1.b. – at “1.5” hours evolving STEMI (same patient)
Tracing #2 – Early Repolarization (Benign Normal Variant)
Tracing #3 – Normal ECG
Conclusion: When faced with the challenge of deciding whether a given tracing is early repolarization or acute STEMI (especially if the changes are subtle). Look for “terminal QRS distortion”. If present, it is highly suspicious for the Acute STEMI.
Click “MARK COMPLETE” or “NEXT”.