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Answer: This patient is suffering from a posteroinferior MI.
The best way to approach ECGs is, like anything else in medicine, systematically. Breaking down each component (rate, rhythm, axis, interval, morphology), we see the following findings on the ECG:
Rate: 90/min
Rhythm: irregularly irregular, no discernible p waves
Axis: normal
ST-T-Q: Hyperacute T waves in leads II/III/aVF; reciprocal ST depression and/or T inversion in lateral leads I, aVL, V5, V6
Hyperacute T waves in 2 or more contiguous leads are STEMI equivalents and indicate an evolving infarct (3).
Inferior MI: The Basics
- Hyperacute T/STE in leads II, III, aVF; reciprocal STD in aVL +/- lead I (2)
- Can involve the vagus nerve and cause AV block/bradycardia
- 80% is due to a dominant RCA lesion, 20% due to LCx lesion
- 40% will have concomitant RV infarction – suspect this with all inferior wall MI
- RV infarction is indicated by:
- STE in V1 (looks directly at the RV) with concurrent STD in V2 – this is highly specific
- STE in lead III > lead II
- R sided leads: STE in V3R-V6R
- If an RV MI is present, avoid nitrates – these patients are preload dependent
Posterior MI:
Posterior infarctions are more often seen in conjunction with other MIs (most commonly inferior) or in isolation (~3%). They are often missed due to the absence of STE, as no ECG lead looks directly at the posterior wall. Instead, look for reciprocal changes in the anterior leads (1):
-
- ST depressions, T-wave inversions in V1-V3
- dominant R wave in V2
- Indicators of posterior MI in the above ECG: Hyperacute T wave and poor R wave progression in V3, ST depression in V2-V4
*8/14/19 Update*
A recent EM/IM graduate who is now doing a cardiology fellowship weighed in on the ECG and offered us his following insights (thanks Dr Greenstein!):
Great review of a fib. From my perspective, there are a few things pointing me away from a fib…
1. Lateral leads are likely just artifact and I don’t think that’s true a fib
2. Looks like there is some regularity to the rhythm. I’ve marched it out for you although I think it’ll be easier with calipers or paper marks
3. If you look at the PACs, they are slightly different morphology. Amplitude, s wave, width of QRS, etc… It’s possible a fib is coming through but I think it’s less likely
References:
- Van Gorselen EO, Verheugt FW, Meursing BT, Oude Ophuis AJ. Posterior myocardial infarction: the dark side of the moon. Neth Heart J. 2007;15:16-21
- Mattu A. ECG’s for the Emergency Physician
- Manno BV, Hakki A, Iskandrian AS, Hare T. Significance of the upright T wave in precordial lead V1in adults with coronary artery disease. J Am Coll Cardiol. 1983;1(5):1213-1215.
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