Serum Cardiac Biomarkers
Creatine kinase (CK) is found in striated muscle and tissues of the brain, kidney, lung, and GI tract. This marker has low sensitivity and specificity for cardiac damage, and total CK levels may be elevated in a number of noncardiac conditions, including trauma,seizures, renal insufficiency, hyperthermia, and hyperthyroidism. As a result, the total CK marker largely has been replaced by cardiac troponins and CK-MB.
CK-MB isoenzyme: CK-MB is cardiac specific and is useful for the early diagnosis of acute myocardial infarction. CK-MB typically is detectable in the serum 4–6 hours after the onset of ischemia, peaks in 12–24 hours, and normalizes in 2–3 days. Like the CK level, the peak CK-MB level does not predict infarct size; however, it can be used to detect early reinfarction since it normalizes 2-3 days after the initial MI. Serial CK-MB levels commonly are obtained at admission to the emergency department and are repeated in 6–12 hours.
Creatine kinase (CK) is found in striated muscle and tissues of the brain, kidney, lung, and GI tract. This marker has low sensitivity and specificity for cardiac damage, and total CK levels may be elevated in a number of noncardiac conditions, including trauma, seizures, renal insufficiency, hyperthermia, and hyperthyroidism. As a result, the total CK marker largely has been replaced by cardiac troponins and CK-MB. CK-MB isoenzyme: CK-MB is cardiac specific and is useful for the early diagnosis of acute myocardial infarction. CK-MB typically is detectable in the serum 4–6 hours after the onset of ischemia, peaks in 12–24 hours, and normalizes in 2–3 days.
Like the CK level, the peak CK-MB level does not predict infarct size; however, it can be used to detect early reinfarction since it normalizes 2-3 days after the initial MI. Serial CK-MB levels commonly are obtained at admission to the emergency department and are repeated in 6–12 hours.
The cardiac troponins typically are measured at emergency department admission and repeated in 6–12 hours. Patients with a normal CK-MB level but elevated troponin levels are considered to have sustained minor myocardial damage, or microinfarction, whereas patients with elevations of both CK-MB and troponins are considered to have had acute myocardial infarction. The cardiac troponins may remain elevated up to 2 weeks after symptom onset, which makes them useful as late markers of recent acute myocardial infarction.
An elevated troponin T or I is helpful for identifying patients at increased risk for death or the development of acute myocardial infarction. Increased risk is related to the high serum troponin levels. The troponins also can help identify low-risk patients who may be sent home with close follow-up. Those with a normal or nearly normal ECG and a normal troponin I test 6 hours after admission had a very low risk of major cardiac events (0.3%) during the next 30 days.
Also:
Elevations of troponin not caused by an acute coronary syndrome
