Cardiac Marker Panel

The American College of Cardiology (ACC) and the American Heart Association (AHA) issued guidelines for the management of patients with unstable angina and non-ST segment elevation myocardial infarction (Circulation 2000; 102:1193-1209). At the same time, a joint committee of the European Society of Cardiology and ACC published a consensus document entitled the "Redefinition of MI" (JACC 2000; 36:959-69). These articles contained the following recommendations regarding cardiac marker laboratory testing.

· Troponin T or I is the preferred cardiac marker.

· CK-MB is an acceptable alternative, if troponin is not available.

· Total creatine kinase (CK) is no longer useful & should be discontinued.

· Troponin should be measured within 6 hours of the onset of symptoms.

· If the first troponin result is negative, a second sample should be obtained between 6 & 12 hours of symptom onset.

· Cardiac Marker results should be available within 30 to 60 minutes.

Based on these recommendations, the following changes are essential in cardiac marker testing.

· Create a new Cardiac Marker Panel for the Emergency Department that includes CK-MB & Troponin at 0, 3 & 6 hours after admission.

· Retain the current Acute Cardiac Injury Panel that includes CK-MB & Troponin at 0, 6 & 12 hours for admitted patients.

· Eliminate total CK from all cardiac panels.

Creation of the new Cardiac Marker Panel with shorter testing intervals facilitates more rapid decision-making. Retention of the 12-hour specimen prevents a missed diagnosis in patients who were late seroconvertors.

The other cardiac marker

· Creatine Phosphokinase (CPK)

o Rises: 4-6 hours

o Peaks: 12-24 hours

o Duration: 4-5 days

o Subunits (Fractionate to CK-MB only if CPK increased)

o CK-MB Fraction (duration for 2-3 days)

o CK-MB over 5% of total CPK suggests Myocardial Injury

· Myoglobin

o Advantage: First cardiac marker to increase

o Disadvantage: Poor Specificity (only helps if negative)

o Rises: 1-2 hours

o Peaks: 4-6 hours

o Duration: 1-2 days

· Glutamic oxaloacetic transaminase (AST, SGOT)

o Peaks: 24-36 hours

o Duration: 5 days

· Lactic Dehydrogenase (LDH)

o Peaks: 24-48 hours

o Duration: 14 days

· White Blood Cell Count

o Predicts adverse events in Unstable Angina

o Morbidity and mortality increase with increased WBCs

o WBC Count >10,000: High risk of adverse event

o WBC Count >15,000: Very high risk of adverse event