STEMI equivalents

(Redirected from Posterior MI)


  • STEMI typically defined by[1]:
    • ≥1 mm (0.1 mV) ST segment elevation in limb leads
    • ≥ 2 mm ST segment elevation in precordial leads
    • Findings present in at least 2 anatomically contiguous leads
  • Several variations from the classic STEMI ECG changes are similarly concerning and considered 'STEMI equivalent'

STEMI Equivalents

Posterior MI

  • RCA (90%), LCA (10%)
  • 12-Lead ECG findings[2]
    • ST-segment depression (horizontal >> downsloping/upsloping)
    • Prominent and broad R wave (>30ms)
    • Relative tall R waves in precordial leads (may find R = S amplitude in V1)
    • R/S wave ratio >1.0 in lead V2
    • Prominent, upright T wave
    • Combination of horizontal ST-segment depression with upright T wave
  • Posterior ECG or 15-lead ECG may be helpful
    • V7: Left posterior axillary line along the 5th ICS
    • V8: Tip of the left scapula line along the 5th ICS
    • V9: Left paraspinal area line along the 5th ICS
  • Posterior ECG findings
    • ≥0.5 mm ST-segment elevation

Posterior MI.jpg

LMCA Occlusion

  • Seen with left main artery lesion[3]
  • Also reported in proximal LAD lesions and severe multivessel coronary artery disease
  • 12-Lead ECG findings
    • ST elevation in aVR ≥ 1mm
    • ST elevation in aVR ≥ V1
    • ST depression typically seen in lateral


De Winter’s T Waves

  • Suggests proximal LAD lesion
  • 12-Lead ECG findings[4]
    • Precordial ST-segment depression at the J-point
    • Tall, peaked, symmetric T waves in the precordial leads
    • Lead aVR shows slight ST-segment elevation in most cases


Sgarbossa's Criteria

  • Used to identify STEMI in the setting of LBBB or pacemaker
  • Original Criteria[5]
    • ≥3 points = 98% probability of STEMI
    • ST elevation ≥1 mm in a lead with upward (concordant) QRS complex - 5 points
    • ST depression ≥1 mm in lead V1, V2, or V3 - 3 points
    • ST elevation ≥5 mm in a lead with downward (discordant) QRS complex - 2 points
  • Smith's modification[6]
    • Changes the 3rd rule of original Sgarbossa's Criteria to be ST depression OR elevation discordant with the QRS complex and with a magnitude of at least 25% of the QRS increases Sn from 52% to 91% at the expense of reducing Sp from 98% to 90%[


Wellens’ Syndrome

  • ECG findings in absence of chest pain, but with recent cardiac chest pain symptoms
  • Represents critical stenosis of the LAD
  • Requires PCI in the next 24-48hr (may evolve more rapidly - observe with serial ECGs)
  • 12-Lead ECG findings[7]
    • Deeply-inverted or biphasic T waves in V2-3
    • Isoelectric or minimally-elevated ST segment (<1 mm)
    • Absent precordial Q waves with preserved R waves
  • Two T wave characteristics:
    • Type A: Biphasic pattern - 25% - Biphasic T-waves
    • Type B: Inversion pattern - 75% - Deeply inverted and symmetric T-waves


No Longer STEMI Equivalents


  • New LBBB alone is no longer a reason to activate the cath lab[8]
  • However, careful workup for ACS should be taken for symptomatic patients with LBBB
  • 12-Lead ECG findings
    • QRS > 0.12 in limb leads
    • Leads
      • Large and wide R waves — leads I, aVL, V5, and V6
      • Small R wave followed by deep S wave —leads II, III, aVF, V1–V3


External Links

See Also


  1. ECC Committee, Subcommittees and Task Forces of the American Heart Association.. 2005 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care — Part 8: Stabilization of the Patient With Acute Coronary Syndromes. Circulation. 2005. 112 (24_suppl):IV–89–IV–110. 2005.
  2. Van Gorselen EO, et al. Posterior myocardial infarction: the dark side of the moon. Neth Heart J. 2007; 15:16-21.
  3. Hennings JR and Fesmire FM. A new electrocardiographic criteria for emergent reperfusion therapy. Am J Emerg Med. 2012; 30(6):994–1000.
  4. de Winter R, et al. A new ECG sign of proximal LAD occlusion. NEJM. 2008; 359:2071–2073.
  5. Sgarbossa E, 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". NEJM. 1996; 334(8):481-7.
  6. Smith, S, et al. 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. 60(6):766-776.
  7. Rhinehardt J, et al. Electrocardiographic manifestations of Wellens' syndrome. Am J Emerg Med. 2002; 20(7):638-43.
  8. Jain S, et al. Utility of left bundle branch block as a diagnostic criterion for acute myocardial infarction. Am J Cardiol. 2011; 107:1111-1116.