A. Tropomyosin – Explanation
Tropomyosin is a protein which regulates actin. It associates with actin in muscle fibers and
regulates muscle contraction by regulating the binding of myosin.
Cardiac enzymes and protein markers
Interpretation of the various cardiac enzymes has now largely been super ceded 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 | 2-4 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 |
