STEMI ECG

“Acute myocardial infarction (MI) historically is defined as a clinical syndrome that meets a certain set of criteria, usually a combination of symptoms, electrocardiographic changes, and cardiac biomarkers in the proper clinical context.”6 The following is a summary of ECG criteria used to diagnose ST-elevation myocardial infarction as defined by the Fourth Universal Definition of Myocardial Infarction.1

Standrad ECG Definition

  • ST-elevation at the J-point in 2 contiguous leads with the cut-point: ≥1 mm in all leads except V2-V3 (or >1mm from prior baseline)1
  • ST elevation V2 –V31≥2 mm in men ≥40 years
  • ≥2.5 mm in men <40 years
  • ≥1.5 mm in women regardless of age.
  • ST-segment elevation in aVR associated with ≥1 mm of ST depression in multiple leads may suggest left main coronary artery (LMCA) stenosis or occlusion.3

Posterior STEMI

  • ST depression in leads V1, V2, or V3 with an associated positive T wave in the standard 12-lead ECG
  • ST elevation of ≥0.5 mm in any posterior (V7, V8, V9) lead is recommended as the cut-off point. ST elevation of ≥1 mm has increased specificity and is recommended as the cut-off point in men aged <40 years.1

Left Bundle Branch Block (LBBB)

Original Sgarbossa Criteria4

  • Concordant ST elevation ≥1 mm in leads with a positive QRS complex = 5 points
  • Concordant ST depression ≥1 mm in leads V1-V3 = 3 points
  • Excessive discordant ST elevation ≥5 mm in leads with a negative QRS complex = 2 points

A score >3 is specific for MI in patients with LBBB. 

Smith criteria5

  • Replaced the 3rd item in Sgarbossa’s criteria to improve accuracy. “≥ 1 lead with ≥ 1 mm ST elevation and proportionally excessive discordant ST elevation, as defined by STE ≥ 25% of the depth of the preceding S-wave (an ST / S ratio of ≤ – 0.25)”
  • Removed the point system making all 3 criteria equal. Presence of any single criteria is deemed 80% sensitive and 99% specific in identifying acute MI in known LBBB.

Left Main Disease

ST-segment elevation in aVR associated with ≥1 mm of ST depression in multiple leads may suggest left main coronary artery (LMCA) stenosis or occlusion.3


Further Reading

Evaluation and Management of ST-Segment Elevation Myocardial Infarction in the Emergency DepartmentDate Release: Jan 2021When a patient presents to the ED with symptoms of STEMI, emergency clinicians must be prepared to initiate coordinated, time-sensitive, and effective diagnostic and treatment strategies, with the ultimate goal of initiation of reperfusion. Includes 4 AMA PRA Category 1 Credits™. CME expires on 01/01/2024


References

  1. Thygesen K, Alpert JS, Jaffe AS, et al. Fourth universal definition of myocardial infarction(2018). Circulation. 2018;138(20):e618-e651. PubMed
  2. Frank M, Sanders C, Berry BP. Evaluation and management of ST-segment elevation myocardial infarction in the emergency department. Emerg Med Pract. 2021;23(1):1-28. Article , PubMed
  3. O’Gara PT, Kushner FG, Ascheim DD, et al. 2013 ACCF/AHA guideline for the management of ST-elevation myocardial infarction: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines. Circulation. 2013;127(4):e362-e425. Article
  4. Sgarbossa EB, Pinski SL, Barbagelata A, et al. Electrocardiographic diagnosis of evolving acute myocardial infarction in the presence of left bundle-branch block. GUSTO-1 (Global utilization of streptokinase and tissue plasminogen activator for occluded coronary arteries) Investigators. N Engl J Med. 1996;334(8):481-487. PubMed
  5. 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;60(6):766-776. PubMed
  6. Sandoval Y, Thygesen K, Jaffe AS. The Universal Definition of Myocardial Infarction: Present and Future. Circulation. 2020 May 5;141(18):1434-1436. doi: 10.1161/CIRCULATIONAHA.120.045708. Epub 2020 May 4. PubMed

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