Acute Coronary Syndrome and ECG Interpretation

Introduction

Acute Coronary Syndrome (ACS) is a term used to describe conditions caused by sudden reduced blood flow to the heart. These conditions include unstable angina (UA), non-ST-segment elevation myocardial infarction (NSTEMI), and ST-segment elevation myocardial infarction (STEMI). The electrocardiogram (ECG) is a crucial tool for diagnosing and distinguishing between these types of ACS.

Key ECG Findings in ACS

1. STEMI (ST-Segment Elevation Myocardial Infarction)

  • Defined by ST-segment elevation in at least two contiguous leads.
  • Possible reciprocal ST depression in opposite leads.
  • May show pathological Q waves later, indicating myocardial necrosis.

2. NSTEMI (Non-ST-Segment Elevation Myocardial Infarction)

  • No ST-segment elevation but may have ST depression or T-wave inversion.
  • Cardiac biomarkers (e.g., troponins) are elevated, confirming myocardial injury.

3. Unstable Angina (UA)

  • Similar ECG changes as NSTEMI (ST depression or T-wave inversion) but with normal cardiac biomarkers.
  • Indicates myocardial ischemia without infarction.

Importance of Early ECG Interpretation

  • Initial ECG should be performed within 10 minutes of suspected ACS presentation.
  • Serial ECGs may be needed if initial results are inconclusive but suspicion remains high.
  • Additional leads (e.g., right-sided or posterior leads) should be considered in some cases (such as suspected right ventricular infarction).

Management Based on ECG Findings

  • STEMI: Requires immediate reperfusion therapy, such as PCI (percutaneous coronary intervention) or fibrinolytic therapy if PCI is unavailable.
  • NSTEMI/UA: Requires risk stratification and medical therapy such as dual antiplatelet therapy (DAPT), anticoagulation, and early invasive strategies if indicated.

Conclusion

ECG is a primary tool in ACS diagnosis and management, helping differentiate between life-threatening STEMI, NSTEMI, and unstable angina. Accurate and prompt ECG evaluation is essential for providing timely treatment and improving patient outcomes.

Source recommendations

1. American College of Cardiology/American Heart Association (ACC/AHA) Guidelines for the Management of Patients With ST-Elevation Myocardial Infarction

  1. https://pubmed.ncbi.nlm.nih.gov/15289388/
  2. https://professional.heart.org/en/science-news/2021-acc-aha-scai-guideline-for-coronary-artery-revascularization
  3. https://www.ahajournals.org/doi/10.1161/cir.0b013e3182742cf6
  4. https://www.sciencedirect.com/science/article/pii/S073510972106157X
  5. https://www.ahajournals.org/doi/10.1161/01.cir.0000134791.68010.fa

2. European Society of Cardiology (ESC) Guidelines for the Management of Acute Coronary Syndromes in Patients Presenting Without Persistent ST-Segment Elevation

  1. https://pubmed.ncbi.nlm.nih.gov/26320110/
  2. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Acute-Coronary-Syndromes-ACS-Guidelines
  3. https://pubmed.ncbi.nlm.nih.gov/32860058/
  4. https://academic.oup.com/eurheartj/article/42/14/1289/5898842
  5. https://pubmed.ncbi.nlm.nih.gov/21873419/

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