Most Important Points About Cardiac Markers Tested In Exam
Cardiac markers is one of the most important as well as the most confusing topic for exam. The following points will clear many controversial MCQs.
1. Myoglobin first comes and first goes (rises first, disappears first). This means that:
A. Myoglobin is the earliest cardiac marker to appear after MI.
B. The investigation of choice within first hour of MI is ECG, followed by myoglobin. (ECG is always the investigation of first choice for myocardial infarction regardless of time).
C. The investigation of choice within first two hours of MI is ECG, followed by myoglobin.
2. Myoglobin has the highest sensitivity but has the lowest specificity.
3. LDH is called “lazy enzyme” because it comes late, and goes late (rises after 24 hours and remains till 14 days).
4. Trop-I has the greatest specificity. That’s why it is the “GOLD STANDARD” test for MI.
5. “CKMB” is useful for confirmation of reinfarction as this enzyme disappears after 72 hours of MI. So, if a patient comes after 72 hours of initial infarction, and you are suspecting a reinfarction, go for “CKMB”.
6. When do the enzymes disappear?
– Myoglobin disappears after 24 to 48 hours.
– CKMB disappears after 72 hours.
– Trop I disappears after 7 – 10 days.
– LDH disappears after 14 days.
Scenerio 1: CKMB of patient is normal. Trop-I is raised. He is 3 – 10 days post MI patient.
Scenerio 2: CKMB and trop – I of patient are normal. LDH is raised. He is 10 – 14 days post-MI patient.