Today, I got to interview Dr. Stephen Smith. Dr. Smith is faculty at the Hennepin Program and author of one of the best books on EKGs in the ED, The ECG in Acute MI.
Dr. Smith's EKG Blog is probably the best free EKG site out there for Emergency Physicians and Intensivists.
Here are the points we covered:
1. Ischemia Doesn't Localize
If you see depressions in just one anatomic area, think reciprocal changes to subtle ST-elevations elsewhere
2. If you see Inferior Depressions, think High Lateral Wall STEMI
here are two good cases from Dr. Smith's Blog:
- Case: This is a 35 yo woman who had LAD occlusion that was very subtle on ECG, but easily seen with inferior ST depression
- Case: This is one of a high lateral MI due to OM-2 occlusion that shows up mostly with inferior ST depression.
3. Lateral Wall STEMIs are often Subtle
- Case: A patient had chest pain, went to his doctor who did an EKG, said it was fine, and sent my friend home. He had a cardiac arrest at home and was resuscitated because of good CPR by his wife. Later, I asked him to find the ECG. I told him I’m pretty sure it was not normal. And here it is: a very subtle high lateral MI detected by subtle ST depression in II and aVF
- Another Case
4. Absolute millimeter criteria for STEMI will often fail you, it is the Pattern that Matters.
5. Benign Early Repolarization and LAD Occlusion can look very similar–You may need to do the math.
Dr. Smith derived this formula:
(1.196 x STE60 in V3 in mm) + (0.059 x computerized QTc in milliseconds) – (0.326 x RA in V4 in mm),
where RA is R-wave amplitude and STE60 is ST elevation at 60ms after the J-point relative to the PR interval.
If the value of the formula is greater than or equal to 23.4, it is MI (Sens, spec, accuracy all around 90%); if less, then it's early repolarization.
- Case: Here is a case that illustrates this, it shows a very subtle anterior STEMI, and how use of the complicated new rule that he developed. One need not use the complicated rule; among other features, it was the long QTc of 455ms that made it unlikely to be normal. The followup ECG is also very instructive.
You can also see a video of the concept
6. If you are calling it BER, there need to be R waves in the Precordial Leads
7. Q-waves can develop instantly after a STEMI
qR waves can develop instantly and are not indicative of poor response to lytics or PCI (J Am Coll Cardiol 1995;25:1084); this concept is not applicable to a QS pattern.
8. If you see a wide (>190 ms) QRS, think Hyperkalemia
9. The treatment for VT with hyper-K is Calcium, Calcium, Calcium
- Check out this Case, it says it all
10. Check Out these Two Other Great Sites
HQMEDED: High Quality Medical Education and Ultrasound
The Prehospital 12-lead ECG Blog which despite the name, is great for all levels