WBR0354

Author	Neeraja Danda M.B.B.S
Exam Type	USMLE Step 2 CK
Main Category	Internal medicine
Sub Category	Cardiovascular
Prompt	A 55 year old male presented to the emergency room with acute chest pain and diaphoresis . Electrocardiogram revealed ST segment elevation in leads V2 – V4 . Aspirin was administered and the patient was sent for coronary angiography, which revealed a 75% stenosis in the left main coronary artery . Angioplasty was performed immediately thereafter. On the fourth day following angioplasty, the patient began to experience chest pain again .Which of the following would be helpful in diagnosing a reinfarction?
Answer A	Troponin
Answer A Explanation	Incorrect Troponin starts to rise at 4-6 hours and remains elevated for 10-14 days. Therefore, elevated troponin within this window would not be specific for reinfarction.
Answer B	Myoglobin
Answer B Explanation	Incorrect Myoglobin can be used to detect reinfarction but it is less specific than CK-MB
Answer C	Electrocardiogram
Answer C Explanation	incorrect Electrocardiogram also helps in diagnosing reinfarction , however CK-MB along with Electrocardiogram is the better option
Answer D	Cardiac auscultation
Answer D Explanation	Incorrect Cardiac auscultation can help in diagnosing pericarditis when pericardial rub is appreciated but it has no value in diagnosing infarction.
Answer E	Electrocardiogram and CK-MB levels
Answer E Explanation	CK MB returns to normal level 2 days after infarction Therefore, it is a useful diagnostic criterion for a second MI outside of a 2 day window.Electrocardiogram will help to confirm the diagnosis by showings new changes, particularly in the ST segments
Right Answer	E
Explanation	Electrocardiogram demonstrates an up to date image of the heart electrical activity. . Cardiac enzymes Troponin, Myoglobin and CK-MB start to rise after infarction of cardiac muscle with various kinetics.The first cardiac injury marker to rise is myoglobin at 1-4 hours and reaches baseline in 1-2 days. CK MB rises at 4-6 hours and becomes normal in 1-2 days. Finally,Troponin starts to rise at 4-6 hours and remains elevated for 10-14 days. Therefore, to diagnose a reinfarction, perform an electrocardiogram and measure CK-MB as the raised levels from previous infarction become normal on the second day. Educational Objective:CK-MB returns to normal levels 2 days after infarction. Therefore, its is a useful diagnostic criterion for a second MI outside of a 2 day window. Electrocardiogram will help to confirm the diagnosis by showing new changes, particularly in the ST segments . References: 66 Master the boards Step 2 Ck second edition Educational Objective: References:
Approved	Yes
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