Troponin
Background
- during contraction of muscle- thick filaments of myosin slide past thin filaments of actin by calcium mediated atp dependent contraction. Released calcium binds to troponin C, T, and I, which regulate muscle contraction.
- troponins not change in trauma, skeletal muscle disease, exercise. Renal failure like ck does.
- troponin C found in all tissue and is not cardiac marker
- troponin T is qualitative assay.
- troponin I is quantitative assay.
Cardiac Enzymes Over Time
| Type | Interval (hours) | Peak Elevation (hours) | Return to Normal |
| Myoglobin | 1-4 | 6-7 | 18-24 hours |
| Troponin I | 3-12 | 10-24 | 3-10 days |
| Troponin T | 3-12 | 10-24 | 5-14 days |
| CK-MB | 4-12 | 12-24 | 2-3 days |
| LDH | 8-12 | 24-48 | 10-14 days |
Differential Diagnosis
Elevated Troponin
True Positive
False (Non-CAD) Positives
- Pericarditis
- Myocarditis
- PE
- CHF
- Sepsis
- Dissection
- Arrhythmias
- CVA
- SAH
- Burns
- Renal failure
- Assume true positive until proven otherwise
- ESRD
- 86% elevated predialysis in troponin-T
- 6% elevated predialysis in troponin-I
- no difference in post-MI troponin-I clearance rate in ESRD vs. normal GFR
- Cardioversion
- Cardiotoxic medications
- Amyloidosis
- Rheumatoid Factor
- Heterophilic antibodies
- Apical ballooning syndrome
- Cardiac procedures (surgery, ablation, pacing, stenting)
- Extreme exertion