ECG Ischemia and Infarction

Overview

Hyperacute TW

Tall relative to R, symmetric, broad

Seen prior to development of STE in STEMI and after normalization of STE in transient STEMI that is in process of recannalizing (Smith ECG post).

TWI

 

STEMI

AHA STEMI Criteria

Leads V2-V3:

  • Men <40 – >2.5 mm STE
  • Men >40 – > 2 mm STE
  • Women – > 1.5 mm STE

All other leads:

  • > 1 mm STE

STE DDx (1)

LVH (most common misdx)

Early repol

LV aneurysm

LBBB

pericarditis

WPW

Brugada

Dissection (ask about sudden/maximal onset, sxs above/below diaphragm, neuro sxs)

Sepsis

SAH

Sub-massive/massive PE (think about PE rfs)

Anterior STEMI vs Early Repol

Can us Smith formula only if no obvious anterior STEMI features :

  • < 5 mm STE
  • Concave upwards ST segment
  • No reciprocal inferior STD
  • No Q waves in V2-V4
  • No anterior TWI
  • No terminal QRS distortion
    • Both V2 and V3 need to have an S-wave or an obvious J-wave

STEMI in LBBB

Smith modified Sgarbossa Criteria (2)

  • Concordant STE of at least 1 mm in 1 lead
  • Concordant STD of at least 1 mm in leads V1-V3
  • Any discordant STE w/ ST/S ratio of < -0.25

or a single criteria rule

  •  if the most discordant ST deviation in any lead with at least 1 mm of STE or STD gives an ST/S ratio < -0.3

Posterior STEMI

Will manifest as ST depression in the R precordial leads (reciprocal change to STE on the posterior wall).

Also can get down-up TW in the R precordial leads along w/ CP sxs – note this is different than Wellens which are up-down biphasic TW in the R precordial leads after resolution of pain indicative of a stenotic but recannalized LAD (Smith ECG Blog on topic)

Inferior STEMI vs pericarditis

Look for any STD in aVL – ~99% sensitive and specific (1)

However there are other causes of inferior STE which also have STD in aVL (WPW, LBBB, paced rhythm, inferior LV aneurysm, limb lead LVH)

ST Evaluation in setting of RBBB or LAFB w/ wide QRS

Suspect LAD occlusion in pts who with RBBB or LAFB who are post arrest or in cardiogenic shock.

STE or depression can be very difficult to discern in this setting.

  • Determine lead which clearly shows the end of QRS/start of ST segment.
  • Draw a vertical line from end of QRS in this lead to corresponding portion of QRS on the rhythm lead
  • Draw vertical lines from this point on rhythm lead complexes to map the QRS-ST transition in all remaining leads
  • Eval for ST changes in each lead based on this point

Here is a Dr. Smith’s ECG post on the topic.

STEMI Equivalent

ACS with occlusion or near occlusion of infarct related artery but in the absence of classic “STEMI” criteria

De Winters TW in LAD occlusion (1)

Precordial STD of at least 1 mm followed by up-sloping ST segments into tall symmetric hyperacute TW

dewinter-t-waves-1

Q Waves

  • Inferior or Lateral MI 
    • Pathologic Q’s – > 1mm wide & 3 mm deep
  • Anteroseptal MI
    • Loss of R waves in V1-V3
    • Poor R-wave progression V1-V6
    • Loss of normal septal Q’s in I, V5, V6
  • Anterior wall MI
    • R wave in V1 w/ maintained normal septal Qs in I, aVL, V5, V6
  • High posterior wall MI
    • Large R’s anteriorly V1-V3
  • Posterobasal wall MI
    • Q changes not seen on standard 12 lead

References

  1. Smith, S. 2013. Updates on the ECG in ACS
  2. 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):766-76.