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Peaked T waves: Hyperacute (STEMI) vs. Early Repolarizaton vs. Hyperkalemia

Posted Jan 12 2010 9:18am
Although there is little high quality data on differentiating these entities, some general insights are useful, and illustrated with the following cases:

The first ECG is one of a 27 y.o. patient who presented with ventricular fibrillation.

ECG #1, hyperkalemia

Because of the large T-waves, this ECG was interpreted as "hyperacute T-waves". However, these T waves are pathognomonic of hyperkalemia because they are peaked, "tented", come to point, have a very flat ST segment, and there is a long QRS (114 ms).

Conventional wisdom (with no hard data, to my knowledge) says that when hyperkalemia has a normal QRS that the QTc should be short. This idea conforms with the complex electrophysiology of hyperkalemia, but may not always be true in real life.

ECG #2, LAD occlusion

In this ECG#2 above, the T-waves are slightly more blunt at the peak, there is a normal QRS duration with a long QTc at 450 ms, the ST segment is straightened (less upward concavity, steeper ST segment) which results in an area under the curve (integral) that is larger than in either hyperkalemia or early repol (i.e., the T-wave is "fat")

Below (ECG #3) is a case of a patient who presented feeling moderately ill:

EKG #3, hyperkalemia, QTc 497 ms, QRS 102 ms

Due to the peaked T-waves, the physicians were immediately concerned for hyperkalemia and sought an old ECG, which they immediately found (shown below, ECG #4):

EKG #4, early repolarization, QTc 455 ms, QRS 82 ms

After viewing this previous ECG, and knowing that the K was 4.5 at the time it was recorded, the physicians believed that the peaked T waves in ECG #3 were this patient's baseline. It is true that early repolarization has tall and relatively peaked T waves, but not to the extent seen in ECG #3. Without seeing them side by side, it is hard to appreciate the difference, but the ST segment in V4 in EKG #3 is flat, making the base of the T wave much more narrow.

In addition, the QRS duration difference is important; the difference in QTc seems to defy conventional wisdom.

There is a definite difference, with EKG#3 pathognomonic for hyperkalemia.
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