STEMIs: ECG Case Conference

Preparation: Plan to spend 45-60 minutes familiarizing yourself with the background information below, key findings on the electrocardiographs, and the progressions of animations on the PowerPoint. Each case builds on foundational concepts of ST changes, vascular distribution, acute management of STEMIs, and ECG evolution following PCI. How to present: For optimal function of graphics and animations, we highly recommend downloading the PowerPoint file to be presented from the desktop app rather than presenting directly from the web browser.  Each case progresses through three or more questions, beginning with an overall interpretation, identification of a generalizable rule, and a clinical integration question.  We recommend a pair-share structure with a junior and senior trainee.  For each successive question, the presenter can elect to have pairs discuss their thoughts and then ask for a volunteer to share or, to expedite the conference, simply ask for an audience response.   Ask a leaner to provide an overall interpretation.  Advance using the keyboard arrows or mouse click to reveal subsequent questions followed by the answers with their accompanying graphics.  You can go back to prior graphics and questions by using the back arrow or scrolling back on the mouse wheel.

Case 1: Anterior STEMI

Official ECG Interpretation:

• • Pre-cath ECG: Sinus rhythm, left axis deviation, PVC, ST-elevation in anterolateral leads (I, aVL, V1-V4), reciprocal depressions in inferior leads (II, III, aVF)
  • Post-cath ECG: Sinus bradycardia, left axis deviation, poor R-wave progression with new Q-waves in V1-3

Diagnosis: Acute Anterior STEMI due to 100% occlusion mid-LAD

Teaching:

• • The anterior wall is supplied by the left anterior descending artery, which is seen electrocardiographically in the precordial leads.
  • Reciprocal depressions can be seen in the inferior leads.
  • If ST elevation is present in V1-V3 with reciprocal ST depression II, III, aVF (> 1 mm), PPV 93% and NPV – 68%².
  • Anterior wall myocardial damage is demonstrated by:
    • Poor R-wave progression in the precordial leads.
    • Any Q in V1-V3 or >30ms and >1mm depth in V4-V6 ¹.

 

Next step in management: Goal door-to-balloon time < 90 minutes. The patient was taken to the cath lab where they underwent balloon angioplasty and stent placement to the mid-LAD with resultant TIMI-3 flow.

Case 2: Lateral STEMI

Official ECG Interpretation:

• • Pre-cath: Sinus tachycardia, normal axis, STE in lateral leads (I, aVL, V4-V6), reciprocal depressions in V1-V3
  • Post-cath: Sinus tachycardia, normal axis, persistent ST depression V2-V5

Diagnosis: Acute Lateral STEMI, 100% occlusion left circumflex

Teaching:

• • The lateral wall is supplied by the left circumflex artery, which is typically depicted electrocardiographically in leads I, aVL, V5, V6. The classic presentation is only seen in ~50% of cases³. Otherwise presents as ST elevation in the inferior leads².
  • Overall, 12-lead ECG demonstrates poor sensitivity for left circumflex involvement.
  • If ST elevation is present in I, aVL, V5, V6 with reciprocal ST depression in V1-V3, PPV 91% and NPV 93%².

 

Next step in management: The goal door-to-balloon time is < 90 minutes. Patient was taken to the cath lab where they underwent balloon angioplasty and stent placement to the proximal left circumflex with resultant TIMI-3 flow.

Case 3: Inferior STEMI

Official ECG Interpretation:

• • Pre-cath: 3rd Degree AV block, right axis deviation, STE in inferior leads (II, III, AVF), reciprocal depressions in I, aVL, V1-V6
  • Post-cath: Sinus brady, normal axis, normal ST-segments (notice return of 1:1 P-QRS)

Diagnosis: Inferior STEMI 100% RCA occlusion, complicated by 3rd degree AV block

Teaching:

• • The inferior wall is supplied by the right coronary artery in approximately 80% of cases vs left circumflex in 20% of cases, which is typically depicted electrocardiographically in leads II, III, aVF⁴.
  • High-degree AV block (2nd or 3rd) is a complication in ~12% of inferior wall MI because the AV nodal artery arises from the right coronary artery⁵.
  • If ST elevation in lead III is > ST elevation in II AND ST depression I, aVL, PPV 94% and NPV 70%².
  • A Q-wave in lead III is not significant. Q-waves must be > 30 ms and > 1 mm of depth in both II and aVF to indicate past MI¹.

 

Next step in management: The goal door-to-balloon time is < 90 minutes. This patient was taken to the cath lab where they had a temporary intravenous pacer placed. They also underwent balloon angioplasty and stent placement to the RCA with resultant TIMI-3 flow.

Case 4: Posterior STEMI

Official ECG Interpretation:

• • Initial ECG: Sinus rhythm, normal axis, dominant R-wave V2-V3 ST elevation inferior leads (II, III, aVF), ST depression V2-V3
  • Posterior leads: 1 mm ST elevation in V7-V9

Diagnosis: Posterior wall MI due to 100% RCA occlusion

Teaching:

• • Involvement of the posterior wall is best evaluated by posterior chest leads (V7-9).
  • Posterior lead ST elevation is defined as > 0.5 mm in 2 or more leads⁶.
  • Isolated posterior wall MI may also present with reciprocal ST depression in V1-V4⁷.

 

Next step in management: Goal door to balloon time < 90 minutes. The patient was taken to the cath lab where they underwent balloon angioplasty and stent placement to the RCA with resultant TIMI-3 flow.

Case 5: Left main stenosis of multi-vessel

Official ECG Interpretation:

• • Initial ECG: Sinus rhythm, normal axis, ST depression (I, II, aVF, V2-V6), ST elevation in aVR

Diagnosis: Subtotal LM occlusion with three-vessel disease

Teaching:

• • LMCA infarctions present with two common phenotypes⁸:
    • Subtotal occlusion: diffuse ST depressions with reciprocal ST elevation in aVR
    • Acute total occlusion: ST elevation in anterior and lateral leads with reciprocal ST depressions in the inferior leads (with or without aVR elevation)
  • ST elevation in aVR > 1mm (but can be absent in ~20-40% of cases).
  • LMCA or severe multivessel disease can affect nuclear perfusion studies, which leads to normalization of tracer uptake as there is diffuse ischemia (false negative study).

 

Next step in management: This patient underwent a three-vessel CABG.