Makindo Medical Notes

Related Subjects: |Atherosclerosis |Ischaemic heart disease |Assessing Chest Pain |ACS - General |ACS - STEMI |ACS - NSTEMI |ACS - GRACE Score |ACS - ECG Changes |ACS -Cardiac Troponins |ACS - Post MI arrhythmias |ACS: Right Ventricular Infarction

⏱️ Timing update: After myocardial injury, high-sensitivity troponin (hs-cTn) typically rises within ~1–3 h, peaks at ~12–24 h, and stays elevated for 7–14 days. (It does not rise “within minutes”). 🧪 Sampling: Use your lab’s validated pathway (0/1 h or 0/2–3 h). If not available, use 0 h + 3–6 h (extend to 12 h if symptoms very recent).

📖 About

• Troponin controls actin–myosin contraction; clinically we measure cTnI and cTnT (not TnC).
• Even tiny necrosis (~1 g myocardium) can be detected with modern hs-assays.

🩺 When and Why to Test

• Indicated if ACS suspected: ischemic chest pain, dyspnoea, syncope/collapse, concerning ECG.
• Use hs-cTn within a structured 0/1 h or 0/2–3 h pathway + clinical/ECG correlation.

📜 Universal Definition of MI (4th)

• Acute myocardial injury: cTn above the 99th percentile with rise/fall.
• Myocardial infarction (MI): acute injury + ischemia evidence (symptoms, ischemic ECG, imaging wall motion loss, or thrombus).
• Differentiate:
  • Type 1 MI = plaque rupture/erosion.
  • Type 2 MI = supply–demand mismatch (e.g., sepsis, anaemia, tachyarrhythmia).

📊 Interpretation (always assay-specific!)

• 99th percentile (URL): sex- and lab-specific. (e.g. Roche hs-cTnT ~14 ng/L).
• Delta (change): A significant rise/fall over 1–3 h = acute injury. Thresholds vary by assay ➝ check lab policy.

🛠️ Practical Pathway (if ECG not diagnostic)

• 0/1 h: ✔ Rule-out if very low baseline + tiny 1-h delta. ✔ Rule-in if high baseline or large 1-h delta. ❓ Otherwise ➝ observe to 2–3 h.
• 0/3–6 h (legacy): No rise by 3–6 h → MI unlikely. Persisting symptoms/ECG changes → continue work-up.
• Combine with risk scores (GRACE, HEART) for admission vs early outpatient testing.

📌 Example (values vary by assay!)

• 🟢 Normal/Low: hs-cTn below URL ≥3 h post-symptoms + tiny delta → rule-out MI.
• 🟡 Intermediate: Borderline elevation/small delta → repeat at 2–3 h, consider imaging/observation.
• 🔴 High/Probable MI: Clearly >URL with significant rise + ischemic features → treat as ACS.

⚠️ Non-ACS Causes of Troponin Rise

• ❤️ Cardiac: HF, tachy/bradyarrhythmias, myocarditis/pericarditis, HCM, valve disease, dissection, cardiac contusion/procedures, drugs (chemo).
• 🫁 Vascular/Respiratory: PE, severe pulmonary HTN, hypoxia.
• 🌍 Systemic: Sepsis/SIRS, stroke/SAH, renal failure (chronically raised), DKA, COPD exacerbation.

📒 Reporting & Pearls

• 🚫 Troponin ≠ MI alone → always use history, ECG, exam, imaging.
• 📉 Chronic elevation (e.g., CKD) without rise/fall = chronic injury.
• ♀ Use sex-specific cut-offs if validated.
• 🕒 Always document symptom onset time – it alters rule-out validity.
• ❌ Avoid CK-MB/myoglobin in hs-cTn era – little added value.

📈 Biomarker Timelines

💡 Safety tips: 🔴 If symptoms/ECG scream ischemia → treat & escalate regardless of a low first troponin. 📏 Always use your hospital’s assay-specific cut-offs and delta rules. ♻️ Repeat testing + clinical judgment = safest strategy.