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 (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

• Occlusive myocardial infarction
  • STEMI
  • NSTEMI

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

See Also

• Cardiac Enzymes
• Acute Coronary Syndrome (Main)

External Links

• Pediatric Emergency Playbook Podcast: Big Labs, Little People

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.