The patient is admitted with a suspected acute myocardial infarction (AMI). In assessing the 12-lead electrocardiogram (ECG) changes, which findings would indicate to the nurse that the patient is in the process of a myocardial infarction (MI)?
Depressed ST-segment on ECG and elevated total CPK
Depressed ST-segment on ECG and normal cardiac enzymes
ST-segment elevation on ECG and elevated CK-MB or troponin levels
Q wave on ECG with normal enzymes and troponin levels
The Correct Answer is C
Rationale:
A. A depressed ST-segment is often associated with ischemia or non-ST elevation myocardial infarction (NSTEMI), not an ongoing MI.
B. A depressed ST-segment with normal cardiac enzymes suggests ischemia rather than an active MI.
C. ST-segment elevation on ECG combined with elevated cardiac biomarkers such as CK-MB or troponin levels is a hallmark of an acute ST-segment elevation myocardial infarction (STEMI), indicating an ongoing MI.
D. A Q wave on ECG indicates an old infarction and is not associated with an acute MI if enzymes and troponin levels are normal.
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Correct Answer is D
Explanation
Rationale:
A. CK-MB is a cardiac enzyme that rises in response to myocardial injury, but it is less specific and takes longer to rise than troponin.
B. BNP is associated with heart failure, not myocardial infarction.
C. Myoglobin is an early marker but is non-specific, as it rises with any muscle damage.
D. Troponin is the most specific and sensitive biomarker for myocardial infarction. It rises within 3-4 hours after myocardial injury and remains elevated for days, making it the most useful test for confirming an MI.
Correct Answer is C
Explanation
Rationale:
A. A depressed ST-segment is often associated with ischemia or non-ST elevation myocardial infarction (NSTEMI), not an ongoing MI.
B. A depressed ST-segment with normal cardiac enzymes suggests ischemia rather than an active MI.
C. ST-segment elevation on ECG combined with elevated cardiac biomarkers such as CK-MB or troponin levels is a hallmark of an acute ST-segment elevation myocardial infarction (STEMI), indicating an ongoing MI.
D. A Q wave on ECG indicates an old infarction and is not associated with an acute MI if enzymes and troponin levels are normal.