USMLE Forum Archives - USMLE Step 2 CK - IM 6
IM 6
TheOne - 10-30-06 18:35
A 62-year-old man is being treated for an acute myocardial infarction. He originally came to the
emergency department with substernal chest pain and diaphoresis. Given his risk factors of
hypertension, diabetes, tobacco use, and family history, he is considered high-risk. An
electrocardiogram in the emergency department reveals a left-bundle branch pattern, and
cardiac enzymes are elevated slightly. After a focused evaluation in the emergency
department, the patient receives intravenous thrombolytics. Although his bundle branch
pattern never resolves, the patient is chest pain-free and hemodynamically stable after
thrombolysis. Two days later, however, the patient reports episodes of recurrent chest
discomfort and shortness of breath overnight. In evaluating for potential myocardial
reinfarction, which of the following is the most appropriate diagnostic test?
A. Creatinine kinase
B. Dynamic EKG changes
C. Lactate dehydrogenase
D. Myoglobin levels
E. Troponin I level
TheOne - 10-30-06 18:35
A 62-year-old man is being treated for an acute myocardial infarction. He originally came to the
emergency department with substernal chest pain and diaphoresis. Given his risk factors of
hypertension, diabetes, tobacco use, and family history, he is considered high-risk. An
electrocardiogram in the emergency department reveals a left-bundle branch pattern, and
cardiac enzymes are elevated slightly. After a focused evaluation in the emergency
department, the patient receives intravenous thrombolytics. Although his bundle branch
pattern never resolves, the patient is chest pain-free and hemodynamically stable after
thrombolysis. Two days later, however, the patient reports episodes of recurrent chest
discomfort and shortness of breath overnight. In evaluating for potential myocardial
reinfarction, which of the following is the most appropriate diagnostic test?
A. Creatinine kinase
B. Dynamic EKG changes
C. Lactate dehydrogenase
D. Myoglobin levels
E. Troponin I level
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#1
Re: IM 6 kingkong - 10-30-06 20:36 I WILL GO WITH THE OPTION (A) SINCE THE CKMB IS A VALUABLE MARKER FOR REINFARCTION.TROPONIN IS AN EXCELLENT MARKER FOR INFARCTION BUT NOT FOR REINFARCTION SINCE IT IS ELEVATED FOR UPTO TEN DAYS.
#2
very good
TheOne - 11-02-06 19:06 The correct answer is A. Reinfarction in a hospitalized patient is evaluated best by
creatinine kinase (CK). CK, total levels and specific MB fraction, are elevated as early as
3 hours after onset of chest pain, and, more importantly, have a duration of no more than
2 days, peaking within 18 to 24 hours. As such, CK levels are easier to track. A sudden
increase in CK levels represents new infarction rather than a delayed effect from a
previous myocardial event.
Dynamic EKG changes (choice B) are not sensitive for infarction. Further, this patient
has a left-bundle branch pattern on EKG, making interpretation of any EKG changes
impossible.
Lactate dehydrogenase (LD) (choice C) and relative amounts of different LD isoforms
are not as common now that more sensitive and specific serum markers are available.
Further, LD remains elevated for 6 to 8 days. An elevated LD in this patient would be
difficult to interpret, as it would not be clear whether the enzymes were still elevated from
the first event.
Myoglobin (choice D) has many characteristics that make it seem an excellent serum
marker for an acute event. It is the first enzyme elevated, often within an hour or two,
peaks relatively early within 6 to 7 hours, and lasts no more than 1 day. It is notoriously
nonspecific, however, and is often elevated in hospitalized patients for unrelated
reasons.
Troponin levels (choice E) increase in 3 to 12 hours, peak in approximately 1 day, and
gradually taper over the next 10 days. And As KingKong said:
TROPONIN IS AN EXCELLENT MARKER FOR INFARCTION BUT NOT FOR REINFARCTION SINCE IT IS ELEVATED FOR UPTO TEN DAYS.
#4
Re: IM 6 bingousmle - 07-19-10 08:51 this patient who has a possible reinfarction so he should be tested for raised CPK MB levels as they alone can be helpful.. so Creatinine kinase
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