Hyperacute T waves are tall, broad based and more symmetrical than normal. There is no absolute size that is too tall to be normal, as it depends on the size of the QRS. It has been suggested that a T:QRS ratio greater than 0.33 in V1-4 is abnormal. A T/R ratio has also been described. T waves in V4-6 should never be taller than the R wave. If in doubt, compare with a previous baseline ECG.
Hyperacute T waves can be the first sign of coronary occlusion. They localise to the affected artery distribution and can have reciprocal changes. They may also occur with Prinzmetal angina, or when the ST segments are on the way back down again after reperfusion.
See also: T and U waves
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This ECG is from a man in his 40s who presented with chest pain since the previous evening, associated with vomiting and diaphoresis. He had recently stopped smoking.
This ECG shows subtle disproportionately tall T waves in V2-V3 and ST depression in V3-6 with slight ST elevation in V1. The cause was a 100% proximal LAD thrombotic occlusion.
This ECG is from an elderly woman who presented with chest pain and shortness of breath.
This ECG shows ST elevation in V2 with hyperacute T waves in V2-3. Even though this does not meet STEMI criteria, it is highly suspicious. Serial troponins did rise, pain was ongoing and the ECG evolved to meet STEMI criteria. A 100% mid-LAD occlusion was found to be the cause. Echo showed widespread wall motion abnormalities and reduced ejection fraction.