Hyperkalemic electrocardiographic changes can occasionally be mistaken for STEMI. Dr. Smith at his ECG blog presents a case here and links to several others, in which recognition of the hyperkalemia was delayed by a trip to the cath lab (none of the patients presented turned out to have ACS) resulting in a bad outcome.
Instance after instance has been reported in which hyperkalemic ECG changes were initially interpreted as STEMI. The differentiation is a little tricky but there are always clues to point to the correct diagnosis, among them wide QRS and peaked T waves.
It is helpful to look at a lot of these tracings and as you do a more easily recognizable pattern emerges. To me, in many examples, there is something about the way the terminal up or down stroke of the wide QRS heads into the T wave that gives the appearance of ST segment displacement. Also, though the T waves are high in amplitude they are peaked rather than rounded and broad based as in true STEMI. Apparently, according to Dr. Smith's post, the pattern has not been studied very systematically but there are many anecdotal reports.
The recognition of this phenomenon is not new. It was first reported in the early 1950s and was termed “the dialyzable current of injury.” One of those early papers is linked here. It is available as free full text and is well worth the read.
A word of caution. Today's performance driven world is hazardous to the diagnostic process. Once a STEMI alert is called all diagnostic reasoning tends to stop. Be aware that hyperkalemia is a great electrocardiographic imitator.