Which is the marker of re infarction in MI
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marker of reinfarction in MI CK-MB troponin
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The answer is well-supported by authoritative sources. Here is a concise, textbook-backed summary:
Marker of Reinfarction in MI
CK-MB (Creatine Kinase-MB isoenzyme) is the classic marker of reinfarction.
Why CK-MB and not Troponin?
The key reason comes down to kinetics:
| Marker | Rise | Peak | Returns to Normal |
|---|---|---|---|
| Troponin (cTnI/cTnT) | 2–4 hrs | 24–48 hrs | 7–10 days |
| CK-MB | 4–6 hrs | 24 hrs | 48–72 hrs |
Because troponin remains elevated for 7–10 days after an index MI, it cannot reliably detect a new infarction occurring within that window — the elevated baseline makes it impossible to identify a fresh rise.
CK-MB, by contrast, returns to normal within 48–72 hours, so if it rises again after normalizing (or shows a ≥20% re-elevation from a nadir), this indicates reinfarction.
"Because of its more rapid decline after the onset of AMI, CK-MB may be useful for the discrimination of early reinfarction during the period that cardiac troponin remains elevated following the index event." — Harrison's Principles of Internal Medicine, 22E
Important nuances:
- Troponin can also be used for reinfarction — a ≥20% rise from the nadir value after an initial decline is accepted as diagnostic of reinfarction by the Universal Definition of MI criteria.
- However, CK-MB remains the preferred/classical answer in exam contexts because of its faster clearance making reinfarction identification more straightforward.
- Henry's Clinical Diagnosis (lab methods reference): "Although more experience has been acquired in testing for reinfarction using CK-MB, which declines more rapidly after an uncomplicated MI than cTn, it appears that the latter can be equally effective in diagnosing reinfarction."
Bottom line for exams: CK-MB is the marker of reinfarction in MI, owing to its shorter half-life and faster return to baseline compared to troponin.
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