Tom Bouthillet, editor-in-chief of the ems12lead.com discusses acute inferior, anterior, lateral and posterior STEMI in a progressive “easy-to-hard” format. Assumes basic knowledge of 12-lead ECG interpretation.
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The following questions were asked by viewers during the webcast with answers provided by Tom Bouthillet.
How does endo, myo or pericarditis make calling a true STEMI more difficult?
It’s usually one or the other but not both. Typically myo/pericarditis will not have reciprocal changes. On those rare occasions where it does localize (which is controversial), it is indistinguishable from STEMI and should be treated as such.
How can you tell if you are looking at chronic ST segment elevation and not acute STEMI?
If it is ST-elevation from a previous myocardial infarction (the so-called “ventricular aneurysm” pattern), the T/QRS ratio is less. In other words, the T-wave will be smaller in amplitude. You also see this pattern with late presenters. The T-wave is smaller because there is less salvageable myocardium. If it is “chronic” ST-elevation from something else (like left ventricular hypertrophy or another STEMI mimic), then you just have to learn the STEMI mimics. That’s why this is hard!
How accurate is the STJ column measurements on ZOLL monitors? Can you be sure that if the listed measurement in the 'STJ' column is greater than 100, you do have at least 1mm of elevation in that lead?
I’m not familiar with this, but if it represents ST-elevation measured at the J-point my advice would be to confirm it with your own eyes! I don’t mind help from a computer, but I always confirm abnormal findings. I think of it almost like comparing notes. It’s interesting if they really break it down to hundredths of millimeters!
How can you tell the difference on a 12-lead between old heart damage and new heart damage?
Typically old heart damage leaves a Q-wave, whereas new heart “injury” results in acute ST-elevation and hyperacute T-waves. In the event that old heart damage leaves persistent ST-elevation the T-wave amplitude will typically be less than we would expect with acute injury.
Capturing false positives is easy, how is your agency capturing those missed and addressing these issues with your medics?
It’s very rare that we miss a STEMI, but it has happened. We have a quarterly multi-disciplinary STEMI meeting at the hospital. The chair of the committee is one of the nurses from the cath lab. We track every STEMI backwards from the cath lab. If they were transported by EMS they look for the prehospital 12-lead in the chart. We also mark the date and time of every “Code STEMI” called from the field and bring it to the meeting, so it’s obvious when EMS misses a STEMI. We address it with non-punitive feedback and education unless there is a pattern of inattention to duty.
Can you post a link for the Axis class?
You mentioned missed STEMIs in the context of NSTEMI. Are all, or most, NSTEMIs at some point intervention eligible? Are there measures possible to catch these missed opportunities?
Not necessarily. There is a fair amount of debate over “conservative” versus “early invasive” strategy for NSTEMI. It depends on local practice, which can vary from cardiologist to cardiologist. They usually look at the patient’s clinical stability, risk factors, cardiac biomarkers, amount of ST-depression, and so on. My point is that many so-called “high risk” NSTEMI patients are really unrecognized STEMIs. Can we catch them? I think we can catch a lot of them! Let’s start with acute posterior STEMI.
Any value in the 15-lead EKG?