|The computer interpretation used CAPS LOCK, and had a lot of "***."|
Cardiology was skeptical, but had him in the cath lab 30 minutes later. My resident put 50 cents down on a LAD occlusion, while I bet him a cup of (free) coffee that this was a classic first diagonal , or high lateral, STEMI. The two cardiology fellows agreed that we were both mistaken, and that they were certain to find a blocked circumflex. While the patient was in the lab the troponin came back as significantly elevated.
A few hours later, the cards fellow calls me back with the cath results.
|No offense to Steve Harvey, but I'm a Dawson kinda guy.|
Nada. Clean cath. "No significant fixed obstructive disease."
Interestingly, however, both ventriculography and an echo revealed hypokinesis of the high anterolateral wall, corresponding to the anatomy suggested by the ECG. He was given a diagnosis of focal myocarditis.
This isn't very common, but we can't say how uncommon. It is still uncommon enough to be worthy of case reports, at least in Texas. We know that about 3% of MIs (i.e. with positive cardiac enzymes) have clean coronary arteries by angiography, but a number of those people likely have spasm or spontaneous reperfusion. The percentage may even be smaller with true STEMI patterns, but we don't know.
The only way in the past to definitively diagnose myocarditis was through endomyocardial biopsy, which has a good number of shortcomings, both in terms of sensitivity, and of complications.
|What could go wrong with this?|
|Uh, yeah, I see it too...|
Now, I understand that the myocarditis can generate ST elevation, likely in the same manner that pericarditis does. I am really surprised, however, that our patient had such distinctive and appropriate reciprocal changes. Nonetheless, an ECG from a case report of myocarditis also shows reciprocal changes:
Turning to Stephan Smith's ECG Blog for some wisdom, I found this observation in "Is it MI or pericarditis?" (There's a lot of overlap between pericarditis and myocarditis, and many people link them on a spectrum; e.g myopericarditis.):
Pericarditis should never be assumed when there is even a hint of reciprocal ST depression. Only localized pericarditis (most pericarditis is "diffuse" inflammation of the entire pericardium) ever has reciprocal ST depression, and localized pericarditis is very rare. I suspect that many cases of "localized pericarditis" are really STEMI that went undiagnosed.
A great review article by Punja 2010 gives a few examples of ST elevation in myocarditis, but neither example shows reciprocal changes.
|Nasty STE in myocarditis, but no ST depression|
The Bottom Line
So, the next time you bring in that "for sure" STEMI, keep in mind there's a (3%*78%=) 2% chance it's myocarditis. Or higher. Or lower.