Cardiac Enzymes: Their Role in Diagnosing Heart Conditions

Introduction

Cardiac enzymes are proteins released into the bloodstream when the heart muscle is damaged. They play a crucial role in diagnosing conditions like heart attacks (myocardial infarctions) and other cardiac disorders. Understanding how they work can help patients comprehend their diagnostic value and clinical significance.

Key Cardiac Enzymes

1. Troponins (Troponin I and Troponin T)

  • These are the most specific markers of heart muscle damage.
  • Even a very small increase in troponin levels can indicate cardiac injury.
  • Troponin levels start rising within 3–4 hours after myocardial injury, peak at 12–24 hours, and can remain elevated for up to 2 weeks.

2. Creatine Kinase-MB (CK-MB)

  • A less specific but still useful enzyme.
  • Levels start rising within 3–6 hours, peak at 12–24 hours, and return to normal within 2–3 days.
  • Useful in detecting recurrent heart attacks.

3. Myoglobin

  • A very early marker, appearing in the blood within 1–2 hours.
  • Not specific to cardiac muscle; can also increase due to muscle injuries.

4. Lactate Dehydrogenase (LDH)

  • Not commonly used today due to its low specificity for heart conditions.

How Cardiac Enzymes Are Used in Diagnosis

Doctors typically perform serial enzyme measurements over time to assess trends rather than relying on a single test. This is especially important in diagnosing heart attacks where timely intervention can be lifesaving.

Other Conditions That May Elevate Cardiac Enzymes

Apart from heart attacks, cardiac enzymes may be elevated in:

  • Myocarditis (inflammation of the heart muscle)
  • Heart failure
  • Severe hypertension
  • Sepsis and shock (due to reduced oxygen supply to the heart)

Conclusion

Cardiac enzyme tests are a fundamental tool in cardiology. Elevated levels, especially of troponins, warrant immediate medical attention as they may indicate a critical event such as a heart attack. If you ever experience symptoms like chest pain, shortness of breath, and dizziness, seek emergency medical care immediately.

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

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

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