“Small” HATW: Proportion and area matters more than heightĭespite long-standing recognition that hyperacute T waves (HATW) are usually the earliest ECG manifestation of occlusion myocardial infarction (OMI), there is still no formal, universal definition of what represents a HATW. It is however recognised that the ratio of T wave amplitude to the preceding complex is of more significance than overall T wave size. As is the case in bundle branch block with “appropriate discordance”, abnormal depolarisation should be followed by abnormal repolarisation. This extends to the context of a low amplitude QRS complex, which should be followed by a relatively low voltage T wave. In addition, the area under the curve (AUC) of the T wave appears more relevant than the overall height. HATWs are wider and generally more symmetric than normal T-waves, and with evolving infarction the ST segment straightens and increases the AUC.
In the right clinical scenario, we believe that HATWs alone are enough to guide a decision regarding reperfusion therapy.
However, if there is uncertainty, serial ECGs should be performed as these changes generally precede classic STE findings or resolve if there is spontaneous reperfusion.
Note: although HATWs are a frequently observed “first sign” of OMI, these changes often persist during ongoing infarction (as is the case above) and their presence does not necessarily signify recent onset. We may lose a substantial amount of myocardium if we continue to wait for evolving changes that meet “STEMI” criteria.
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