Question

Case Study

Time	Myoglobin	Tn I	CK-MB
1 day	-	++	+
2 day	-	+++	-
3 day	-	++	-
6 day	-	+	-
10 day	+	++	-

Please answer the following questions:

1. Why is the myoglobin negative in the first sample?
2. Why is the CK-MB negative in the second sample?
3. Give an explanation for the increase in myoglobin and TnI on the 10th day.
4. Did this patient have a myocardial infarction? Explain

Answer 1

When an insult occurs to the heart ,it can be easily detected by the presence of certain blood markers like Trop T,Trop I,CPK -MB,Myoglobin

The myoglobin starts raising in the first 4 hours of attack and can be found in the blood for 9 hours only.Checking it after that will be negative.This sample was negative because it was done in the first day (may be at or around 24 hours)

The CK-MB starts raising in the blood in 3 to 6 hours and peaks at 20 to 24 hours.Checking this in the first day will give a positive result. But this patient's sample is tested on second day which shows a negative result.

As myoglobin is found only for first 9 hours in the blood and it comes to normal after 1 day or 24 hours.In case of elevation again it may indicate a recurrent injury.It rises both in the case of skeletal muscle injury or cardiac muscle injury. Troponin I starts raising at 3 to 8 hours and peaks around 14 to 18 hours.It comes to normal in 3 to 5 days.It remains elevated for 10 days in case of an infarction. Troponin is the best marker for acute myocardial infraction

The myoglobin alone cannot be a diagnostic way to confirm a MI ,a Trop I test along with myoglobin when positive is a clear and confirmatory way to myocardial infarction (Troponin I gets released only when the cardiac cells die)