Where does doming of the ST (segment) occur in an electrocardiogram (ECG)?

ST Segment Doming in ECG

ST segment doming (convex upward ST elevation) typically occurs in leads overlying the area of myocardial injury during acute myocardial infarction, with the specific leads affected depending on which coronary artery is occluded and the location of the occlusion.

Characteristics of ST Segment Doming

• ST segment doming refers to a convex upward (non-concave) ST elevation pattern that is more commonly associated with acute myocardial infarction compared to the concave upward ST elevation often seen in non-AMI conditions 1
• The morphology of ST elevation is a critical distinguishing feature, with non-concave (domed) ST elevation significantly more common in acute myocardial infarction patterns (p<0.00001) 1

Location of ST Segment Doming Based on Affected Vessel

Anterior Wall Infarction (Left Anterior Descending Coronary Artery)

• In proximal LAD occlusion (above first septal and diagonal branches):

  • ST doming appears in leads V1-V4, I, aVL, and often aVR 2
  • The ST-segment spatial vector is directed superiorly and to the left 2
  • Reciprocal ST depression occurs in leads II, III, aVF, and often V5 2

• In mid-LAD occlusion (between first septal and first diagonal branches):

  • ST doming appears in leads V2-V4 and aVL, but not in V1 2
  • The ST-segment vector is directed toward aVL 2
  • Reciprocal ST depression appears in lead III 2

• In distal LAD occlusion (below first septal and first diagonal branches):

  • ST doming appears in leads V3-V6 2
  • Less prominent ST elevation in V2 compared to more proximal occlusions 2
  • ST segment may also be elevated in leads II, III, and aVF due to inferior orientation of the ST vector 2

Inferior Wall Infarction

• In right coronary artery (RCA) occlusion:

  • ST doming appears in leads II, III, and aVF 2
  • Greater ST elevation in lead III than in lead II 2
  • Often associated with reciprocal ST depression in leads I and aVL 2, 3

• In proximal RCA occlusion with right ventricular involvement:

  • ST doming also appears in right-sided chest leads V3R and V4R, and often in V1 2
  • The ST vector is directed inferiorly, to the right, and anteriorly 2

• In left circumflex coronary artery (LCx) occlusion:

  • ST doming appears in leads II, III, and aVF 2
  • Less ST depression in leads I and aVL compared to RCA occlusion 3
  • The absence of significant ST depression in lead aVL is most common in proximal circumflex obstruction 3

Posterior Wall Infarction

• ST depression (reciprocal changes) in leads V1-V3 may represent posterior wall infarction 4
• This pattern may be the initial ECG finding of posterolateral infarction 4

Clinical Significance of ST Segment Doming

• The total ST segment elevation is typically greater in AMI (15.3 mm) compared to non-AMI conditions (7.4 mm) 1
• Total ST segment deviation (sum of ST elevation and depression) is significantly greater in AMI syndromes (17.8 mm vs 10.5 mm in non-AMI syndromes) 1
• ST depression in lateral leads (I, aVL, V5, V6) in patients with non-ST elevation MI predicts worse in-hospital outcomes 5

Important Considerations

• The precise localization of the spatial vector of the ST-segment shift helps determine the location of the ischemic/infarcted region 2
• Combined anterior and inferior ST elevation may represent either proximal RCA occlusion or mid-to-distal LAD occlusion 6
• Despite greater ST elevation, patients with combined anterior and inferior ST elevation often have limited infarct size and preserved left ventricular function 6
• ST segment doming should be differentiated from early repolarization, which typically shows concave upward ST elevation 2