When we take a class in STEMI recognition, the ECGs, once you know how to read them, are all pretty clear cut. You can flash the 12-leads on the screen and a well- taught class will call out in unision "Inferior, Anterior, Anterior, Inferior, Lateral," etc. You get tricky and you throw in the ST imposters, but they catch on. "Left Bundle, Right Bundle, LVH, Inferior, Anterior, Left Bundle," etc.
The problem is when you get back on the street not all 12-leads are so cut and dried. I'm been sort of lucky lately in that I've had some idiot-proof STEMIs. Take this one for instance:
Or this one:
In what is becomming one of my favorite expressions regarding STEMIs. "Not Subtle."
Unfortunately, many of the real world 12-leads can be classified as very subtle. I've seen 12-leads that I wouldn't call STEMIs that turned out to be, and some I would call STEMIs that turned out to have negative cardiac enzeyemes and clear arties.
The other day I came across a new study just published in the American Journal of Cardiology. Differentiating ST elevation myocardial infarction and nonischemic causes of ST elevation by analyzing the presenting electrocardiogram in the February 2009 issue.
Here's what it was about. They recruited 15 experienced cardiologists from across the world and gave them each 116 ECGs that had ST elevation of some sort or another whether it was a true STEMI or imposters like LVH or early repolarization and asked them, assuming the generaic patient had chest pain, to decide whether or not they should be sent to the cath lab or not based on the ECG. And if they were not going to send them to the cath lab, they had to check one of 8 reasons why not.
Of the 116 only 8 were STEMIs based on the patient's final charts. The rest were nonishemic ST elevations.
The cardiologists recommended from 7.8% to 33% of the patients go to the cath lab with an average of 19% being sent. And when it came to assigning reasons the researchers found a wide varience in the cardiologists' interpreations of the same ECGs.
The study includes 5 sample ECGs where the reader can make their pick and then read how the cardiologists saw it.
Only 5 of 15 called this one correctly. (Answer to follow)
The study's bottom line:
This study’s findings reflect the diagnostic limitations encountered by cardiologists when the ECG is used as the sole diagnostic tool for STEMI. If experienced readers, using the current criteria and guidelines, cannot accurately and consistently distinguish between STEMI and NISTE, less-experienced readers cannot be expected to do so.
So take heart, paramedics, we aren't expected to be seers. Just do the best you can to identify what you can. Cast a wide net when you do your 12-leads. Do serial 12-leads. One that is not obvious can soon grow into a not subtle one. Call the obvious ones, and bring attention to the possible ones. Evaluate based on patient presentation and ECG.
