D. Component of the thin filaments – Explanation
The other components of thin filaments are actin and tropomyosin. Thick filaments are primarily
composed of myosin.
Cardiac enzymes and protein markers
Interpretation of the various cardiac enzymes has now largely been superceded by the introduction
of troponin T and I. Questions still however commonly appear in the MRCP
Key points for the exam
- myoglobin is the first to rise
- CK-MB is useful to look for reinfarction as it returns to normal after 2-3 days (troponin T remains elevated for up to 10 days)
| Begins to rise | Peak value | Returns to normal | |
| Myoglobin | 1-2 hours | 6-8 hours | 1-2 days |
| CK-MB | 2-6 hours | 16-20 hours | 2-3 days |
| CK | 4-8 hours | 16-24 hours | 3-4 days |
| Trop T | 4-6 hours | 12-24 hours | 7-10 days |
| AST | 12-24 hours | 36-48 hours | 3-4 days |
| LDH | 24-48 hours | 72 hours | 8-10 days |
