Tuesday, February 16, 2021

A 30-something with inferior ST Elevation. OMI? Pericarditis? Normal Variant ST Elevation?

This ECG was texted to me with the information that it was recorded on a 30-something male who presented to the ED with bilateral chest tightness.  

There is some inferior ST elevation.  There is a Q-wave in lead III.  
The ECG is certainly suggestive of inferior OMI.
Or is it Normal ST Elevation?  Or Pericarditis?
The physician had only moderate suspicion due to absence of ST depression in aVL
What do you think?


Meyers interpretation: (all I know is 30-something male with bilateral chest tightness): The lack of hyperacute T waves and lack of STD or TWI in aVL makes this inferior STE not definitive for OMI for me yet. I am not sure between normal variant and possible pericarditis, there are some features of each. I would need more clinical info, repeat ECGs, trops, echo, etc.







Smith: I agreed and thought that it was probably not inferior OMI due to (see references):

1) Absence of ST depression in aVL [99% sensitive for inferior OMI in our study (1, 2)]

2) Absence of T-wave inversion in aVL [also 99% sensitive in our study (1)]

3) Small T-wave in lead III

However, I was not entirely certain because of:

1) Straight ST Segments in all of II, III, and aVF (absence of upward concavity is unusual in normal variant STE and in pericarditis. [Convex ST segments were seen in only 7% of pericarditis in Amal Mattu's study; did not assess straight segments. (2)]

2) Terminal QRS distortion in aVF (I have previously studied terminal QRS distortion in lead V2 and V3 as never occurring when normal variant STE is in leads V2-V4, but have noticed more and more that it is at least a soft sign of OMI in other leads).  See this blog postThis appears to be what Amal Mattu calls the "RT Checkmark Sign"(2, 3) (I will ask Amal and edit it later if I'm wrong.) 

There is Spodick's sign, which is a downsloping of the baseline T-P segment, in several leads.  This has long been associated with pericarditis but without much evidence until recently.  In the 2020 study by Amal Mattu, referenced below, it occurred in 5% of OMI and 29% of pericarditis).(2)  They did not study normal variant STE; it may be very difficult even in the setting of a study to differentiate normal variant from pericarditis as an outcome measure.

Clinical Course

I recommended a formal bubble contrast echocardiogram, serial troponins, and serial ECGs.

Serial ECGs were unchanged.

The echo was normal.

All Abbott high sensitivity troponin I were below the level of detection.

Epilogue

The pain resolved.  The patient had had some viral symptoms, and for this reason was diagnosed with pericarditis and treated with colchicine.

Comment: I have my doubts about pericarditis here: 

1) Pain was not pleuritic, positional, or sharp, and also was not persistent.  Pressure pain where MI is ruled out is more likely to be esophageal.

2) There is no PR depression

3) The ST elevation is far more in inferior than in lateral leads.

4) The ST/T ratio in V6 is less than 25%

I think that normal variant ST elevation (early repolarization) is more likely.  


Final thoughts and New Study differentiating Pericarditis from OMI

Is it important to differentiate pericarditis from normal variant ST Elevation?  It can be!

Read this important post written by Pendell Meyers when he was a medical student:

31 Year Old Male with RUQ Pain and a History of Pericarditis. Submitted by a Med Student, with Great Commentary on Bias!

3 References

2 Studies comparing acute OMI to pericarditis, one by Smith, one by Amal Mattu.  Unfortunately, since it is very difficult to make a definite diagnosis of pericarditis, neither study could even attempt to differentiate pericarditis from normal variant ST Elevation, and it is possible that a large percentage of patients in both studies had normal variant STE and non-cardiac chest pain.

1) Bischof JE, Worrall C, Thompson P, Marti D, Smith SW. ST depression in lead aVL differentiates inferior ST-elevation myocardial infarction from pericarditis. Am J Emerg Med 2016;34(2):149–54. Available from: http://dx.doi.org/10.1016/j.ajem.2015.09.035

This study showed that ANY ST depression in lead aVL is highly sensitive for inferior OMI, and that zero patients with pericarditis had this feature.

Of the 154 patients with catheterization laboratory diagnosis of inferior STEMI, 154 patients (sensitivity, 100%; CI, 98%-100%) had some degree of ST depression in lead aVL (at least 0.25mm).  In addition, all 154 patients demonstrated T-wave inversion in lead aVL (sensitivity, 100%; CI, 98%-100%).  Of the 49 pericarditis patients, zero (0%) had any ST-segment depression in lead aVL (CI, 0%-7%), and 7 (14%) of 49 (CI, 7%-27%) had T-wave inversion in aVL.  ------Of an additional 272 inferior OMI from a different cohort, 267 (98%) had STD in aVL.   

2) Witting MD, Hu KM, Westreich AA, Tewelde S, Farzad A, Mattu A. Evaluation of Spodick’s Sign and Other Electrocardiographic Findings as Indicators of STEMI and Pericarditis. J Emerg Med 58(4):562-569; April 2020;Available from: http://dx.doi.org/10.1016/j.jemermed.2020.01.017

Note that, in the Witting study, 3/42 pericarditis patients had ST depression.  It is not specified in what lead the ST depression was found.  Bischof et al. found zero STD in aVL.  

3) Lee DH, Walsh B, Smith SW. Terminal QRS distortion is present in anterior myocardial infarction but absent in early repolarization. Am J Emerg Med 34(11):2182-2185; November 2016; Available from: http://dx.doi.org/10.1016/j.ajem.2016.08.053


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