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 do not change in trauma, skeletal muscle disease, exercise
- Troponin C found in all tissue and is not cardiac marker
- Troponin T is qualitative assay
- Troponin I is quantitative assay
- High sensitivity troponin T (hsTnT) is a quantitative assay
Cardiac Enzymes Over Time
| Type | Interval | Peak Elevation | Return to Normal |
| Myoglobin | 1-4h | 6-7h | 18-24h |
| Troponin I | 3-12 | 10-24 | 3-10d |
| Troponin T | 3-12 | 10-24 | 5-14d |
| CK-MB | 4-12 | 12-24 | 48-72 |
| LDH | 8-12 | 24-48 | 10-14d |
Differential Diagnosis
Elevated Troponin
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
References
- Jain N, Hedayati SS. How should clinicians interpret cardiac troponin values in patients with ESRD? Seminars in dialysis. 2011;24(4):398-400. doi:10.1111/j.1525-139X.2011.00912.x.
- Ellis K, Dreisbach AW, Lertora JL. Plasma elimination of cardiac troponin I in end-stage renal disease. South Med J. 2001 Oct;94(10):993-6. PubMed PMID: 11702827.
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