♦️ *Cardiac Biomarkers*♦️ *1. Troponin* • Definition: A protein released into the bloodstream when cardiac muscle is damaged. • Clinical Significance: • Best indicator of acute myocardial infarction (MI). • Reference Range: 0–0.4 ng/mL • > 0.4 ng/mL suggests myocardial infarction. • Peak Time: Remains elevated for up to 3 weeks. *2. CK-MB (Creatine Kinase–MB Isoenzyme)* • Definition: An enzyme released when the heart, muscles, or brain are damaged. • Clinical Significance: • Cardiac-specific isoenzyme, but less reliable than Troponin for diagnosing MI. • Reference Range: 0–5 ng/mL • Peak Time: 24 hours post-injury. *3. Myoglobin* • Definition: A protein found in both cardiac and skeletal muscle. • Clinical Significance: • Not specific to cardiac injury, but a negative result is helpful in ruling out MI. • Reference Range: 5–70 ng/mL • Peak Time: 12 hours. 💡 Tip: “Myoglobin = Muscle” – think of skeletal and cardiac muscle involvement. *4. BNP (Brain Natriuretic Peptide)* • Definition: A peptide released by the ventricles when overstretched due to fluid overload. • Clinical Significance: • Indicates heart failure (HF) severity. • Reference Ranges: • Normal: < 100 pg/mL • Mild HF: 100–300 pg/mL • Moderate HF: 300–700 pg/mL • Severe HF: > 700 pg/mL