QUICK TIPS on STEMI equivalents

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QUICK TIPS on STEMI equivalents – A Medical Student Clinical Pearl

Ilya Abelev

MD Candidate, Class of 2022

Dalhousie Medical School New Brunswick

Reviewed by Dr. Jay Mekwan

Copyedited by Dr. Mandy Peach

 

Why recognize STEMI’s?2

STEMI’s indicate an infarction pattern on ECG, and can guide emergency physicians to identify patients who would benefit from emergent catheterization and revascularization.

What is a STEMI?

(S-T Segment Elevation Myocardial Infarction)

A patient presents with clinical symptoms consistent with an acute coronary syndrome together with S-T segment elevation (STE) on ECG or a new LBBB.

What is a STEMI equivalent?

A STEMI equivalent is an ECG pattern suggestive of ischemia that should trigger emergency physicians to consult specialists such as interventional cardiologists for revascularization interventions – similar to a STEMI.

MI Definition1

• ≥ 2.5 mm STE in V2-V3 for males < 40 years*
• ≥ 2 mm STE in V2- V3 for males ≥ 40 years*
• ≥ 1.5 mm STE in V2-V3 for females regardless of age*
• ≥ 1 mm STE all other leads

• New J-point elevation ≥ 1 mm from prior ECG should be considered ischemic
• The J-point is defined as the junction between the QRS termination and the ST-segment onset, and the ST-segment should be measured against the isoelectric TP segment (assuming a stable baseline)3

J point in a) normal; b) c) J point elevation; d) J point depression; e) with J wave (Osborn wave)

Osborn wave: Characteristically seen in hypothermia (typically T < 30C), but they are not pathognomonic (4)

Mnemonic for Stemi Equivalents – PTSD (5)

  1. Posterior MI
  2. T wave Abnormalities
  3. Sgarbossa Criteria
  4. Diffuse ST depression with ST elevation in AVR

Posterior MI (1,6)

“Posterior MIs are easily missed because of the absence of any ST elevation. Posterior involvement is estimated to occur in 15-21% of all acute myocardial infarctions and in isolation ~3% of the time, typically due to occlusion of the left circumflex or right coronary arteries.”

More Information(7)

“As the posterior myocardium is not directly visualised by the standard 12-lead ECG, reciprocal changes of STEMI are sought in the anteroseptal leads V1-3.”

Posterior MI is suggested by the following changes in V1-3:

  1. Horizontal ST depression
  2. Tall, broad R waves (>30ms)
  3. Upright T waves
  4. Dominant R wave (R/S ratio > 1) in V2” (7)

Image illustrating reciprocal changes in V2 and how a ST depression in V2 can appear like a STEMI when flipped (reciprocal)

Where to expect reciprocal changes?

PAILS (8)

Posterior MI – anterior reciprocal changes
Anterior MI – inferior reciprocal changes
Inferior MI – lateral reciprocal changes

Lateral MI <-> inferior or septal reciprocal changes*** exception to mnemonic
Septal MI – posterior reciprocal changes

 

T wave abnormalities

de Winter T-waves (9,10)

Key 12-Lead Features

  1. “J-Point depression with up-sloping ST segments.
  2. Tall, prominent, symmetric T waves in the precordial leads.
  3. Upsloping ST segment depression > 1mm at the J-point in the precordial leads.
  4. Absence of ST elevation in the precordial leads.
  5. ST segment elevation (0.5mm-1mm) in aVR.
  6. “Normal” STEMI morphology may precede or follow the DeWinter pattern.”

 

Wellens Syndrome(11)

Rhinehart et al (2002) describe the following Diagnostic criteria(12) for Wellens syndrome:

• “Deeply inverted or biphasic T waves in V2-3 (may extend to V1-6)
• ECG pattern present in pain-free state
• Isoelectric or minimally-elevated ST segment (< 1mm)
• No precordial Q waves
• Preserved precordial R wave progression
• Recent history of angina
• Normal or slightly elevated serum cardiac markers”

“There are two patterns of T-wave abnormality in Wellens syndrome:

Type A/1 – Biphasic, with initial positivity and terminal negativity (25% of cases)
Type B/2 – Deeply and symmetrically inverted (75% of cases)”

Sgarbossa Criteria(13,14)

In patients with left bundle branch block (LBBB) or ventricular paced rhythm, infarct diagnosis based on the ECG can be difficult
Abnormal depolarisation should be followed by abnormal repolarisation, manifesting as ST-segment and T-wave deviations that do not necessarily indicate acute ischaemia (“appropriate discordance”)

  1. Concordant ST elevation > 1mm in leads with a positive QRS complex (score 5)

  1. Concordant ST depression > 1 mm in V1-V3 (score 3)

  1. Excessively discordant ST elevation > 5 mm in leads with a -ve QRS complex (score 2)

“These criteria are specific, but not sensitive (36%) for myocardial infarction. A total score of ≥ 3 is reported to have a specificity of 90% for diagnosing myocardial infarction.”(13)

Diffuse ST depression with ST elevation in AVR(1)

“STE ≥ 1 mm in aVR or V1 with STD ≥ 1 mm in ≥ 6 leads can suggest left main coronary artery insufficiency, proximal LAD insufficiency, or triple vessel disease, especially if accompanied by pathologic Q-waves, hemodynamic compromise, and/or refractory symptoms.”

• Widespread deep ST depression involving V2-6, I, II, aVL
• ST elevation in aVR > V1

 

Examples of STEMI Equivalents(16): Resource to test knowledge of STEMI equivalents

Conclusion:

  1. Definition of MI varies by age and sex
  2. Use PTSD mnemonic to remember the STEMI equivalents.
    a. Use PAILS to remember appropriate location of reciprocal changes
  3. Initiate appropriate consultation to revascularize/ stent for both STEMI and STEMI equivalents

 

References

  1. Daniel Kreider; Jeremy Berberian. STEMI Equivalents: Can’t-Miss Patterns EMRA [Internet]. [cited 2022 Feb 19]. Available from: https://www.emra.org/emresident/article/stemi-equivalents/
  2. Thygesen K, Alpert JS, Jaffe AS, Chaitman BR, Bax JJ, Morrow DA, et al. Fourth Universal Definition of Myocardial Infarction (2018). Circulation. 2018 Nov 13;138(20):e618–51.
  3. J point ECG Interval • LITFL • ECG Library Basics [Internet]. [cited 2022 Feb 19]. Available from: https://litfl.com/j-point-ecg-library/
  4. Slovis C, Jenkins R. Conditions not primarily affecting the heart. BMJ. 2002;
  5. STEMI Equivalents for ECGs – YouTube [Internet]. [cited 2022 Feb 19]. Available from: https://www.youtube.com/watch?v=lH19cYBdvaQ
  6. van Gorselen EOF, Verheugt FWA, Meursing BTJ, Oude Ophuis AJM. Posterior myocardial infarction: the dark side of the moon. Neth Heart J. 2007;
  7. Posterior Myocardial Infarction • LITFL • ECG Library Diagnosis [Internet]. [cited 2022 Feb 19]. Available from: https://litfl.com/posterior-myocardial-infarction-ecg-library/
  8. Tiny Tips: STEMI? Don’t forget your PAILS! – CanadiEM [Internet]. [cited 2022 Feb 19]. Available from: https://canadiem.org/chest-pain-pails/
  9. de Winter RJ, Verouden NJW, Wellens HJJ, Wilde AAM. A New ECG Sign of Proximal LAD Occlusion. N Engl J Med. 2008;
  10. DeWinter’s T-Waves [Internet]. [cited 2022 Feb 19]. Available from: https://handbook.bcehs.ca/clinical-practice-guidelines/pr-clinical-procedure-guide/pr16-12-lead-ecgs/stemis-equivalents-imposters/stemi-equivalents/dewinters-t-waves/
  11. Wellens Syndrome: A Historical Literature Review – Dr. Jason West [Internet]. [cited 2022 Feb 19]. Available from: https://jacobiem.org/wellens-syndrome-a-historical-literature-review-dr-jason-west/
  12. Rhinehardt J, Brady WJ, Perron AD, Mattu A. Electrocardiographic manifestations of Wellens’ syndrome. Am J Emerg Med. 2002;
  13. Smith SW, Dodd KW, Henry TD, Dvorak DM, Pearce LA. Diagnosis of ST-elevation myocardial infarction in the presence of left bundle branch block with the ST-elevation to S-wave ratio in a modified sgarbossa rule. Ann Emerg Med. 2012;
  14. Sgarbossa Criteria • LITFL • ECG Library Diagnosis [Internet]. [cited 2022 Feb 19]. Available from: https://litfl.com/sgarbossa-criteria-ecg-library/
  15. Sgarbossa Criteria – MEDZCOOL – YouTube [Internet]. [cited 2022 Feb 19]. Available from: https://www.youtube.com/watch?v=oLFJy1e9WWI&t=135s
  16. STEMI Equivalents — Maimonides Emergency Medicine Residency [Internet]. [cited 2022 Feb 19]. Available from: https://www.maimonidesem.org/blog/stemi-equivalents-1

 

 

 

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