ST-Elevation Myocardial Infarction (STEMI) and ECG Findings

Introduction

ST-Elevation Myocardial Infarction (STEMI) is a severe form of heart attack caused by the complete blockage of a coronary artery. Prompt diagnosis and treatment are critical to prevent heart muscle damage and complications.

Recognizing STEMI on an ECG

Electrocardiography (ECG) is the primary tool for diagnosing STEMI. Key ECG changes include:

1. ST-Segment Elevation

• Elevation of the ST segment in at least two contiguous leads:
  • Anterior STEMI (Leads: V1-V4) → Blockage in the left anterior descending artery (LAD)
  • Inferior STEMI (Leads: II, III, aVF) → Right coronary artery (RCA) or left circumflex artery (LCX) involvement
  • Lateral STEMI (Leads: I, aVL, V5, V6) → Blockage in the left circumflex artery (LCX)
  • Posterior STEMI (Reciprocal ST depression in V1-V3, tall R waves in V1-V2) → Often caused by LCX or RCA occlusion

2. Reciprocal ST Depression

• Helps confirm STEMI by showing opposing ST-segment depressions in leads opposite to the infarcted area.

3. Pathological Q Waves (Late Finding)

• Develops hours to days after infarction, representing tissue necrosis.

4. Hyperacute T Waves

• Early sign of ischemia, often preceding ST-segment elevation.

5. T-Wave Inversion

• Late-stage change after reperfusion or infarct healing.

Immediate Management

If STEMI is confirmed on ECG, immediate action is necessary: 1. Emergency Reperfusion Therapy: - Percutaneous Coronary Intervention (PCI): Preferred within 90 minutes of first medical contact. - Thrombolysis: Considered if PCI is unavailable within the optimal time frame. 2. Medications: - Aspirin + P2Y12 inhibitors: Prevent further clotting. - Heparin: Reduces clot formation. - Beta-blockers: Reduces heart strain. - Nitrates: Relieve chest pain.

Conclusion

Recognizing STEMI on ECG is crucial for rapid intervention. If you suspect a heart attack, call emergency services immediately. Proper and timely treatment significantly improves survival outcomes.

Source recommendations

1. American Heart Association Guidelines for Myocardial Infarction

1. https://www.heart.org/en/health-topics/heart-attack
2. https://www.ahajournals.org/doi/10.1161/01.cir.94.9.2341
3. https://www.heart.org/en/health-topics/heart-attack/about-heart-attacks
4. https://professional.heart.org/en/guidelines-statements
5. https://www.ahajournals.org/doi/10.1161/cir.0000000000001030

2. European Society of Cardiology Guidelines on Acute Coronary Syndromes

1. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Acute-Coronary-Syndromes-ACS-Guidelines
2. https://academic.oup.com/eurheartj/article/44/38/3720/7243210
3. https://pubmed.ncbi.nlm.nih.gov/37622654/
4. https://academic.oup.com/eurheartj/article/42/14/1289/5898842
5. https://pubmed.ncbi.nlm.nih.gov/32860058/