Cardiac Markers in the Chest Pain Unit

Newer markers, such as the cTns and CK-MB subforms, could further enhance the process of care in the low to moderate risk undifferentiated chest pain population. With markers that are more sensitive, cardiac-specific, and (in some cases) detected earlier than CK-MB, the standard observation time for definitive rule-out of MI could be reduced from 9-12 h to 6-8 h.

The duration of symptoms before presentation varies widely from patient to patient. In the ED or Chest Pain Unit, then, for the earliest and most sensitive and specific diagnosis of myocardial necrosis, the use of a panel of markers that includes myoglobin or MB subforms as a very early marker, CK-MB mass (4-6 h), and TnT or TnI (4-8 + hours) could be ideal (Fig. 4). The Diagnostic Marker Cooperative Study prospectively compared the sensitivity and specificity of myoglobin, CK-MB subforms, CK-MB mass, and cTnI and cTnT at various times from symptom onset across the spectrum of patients presenting to EDs with chest pain. Of 995 patients, 12.5% had MI by CK-MB mass assay. Overall, the sensitivity for detecting MI was highest for the CK-MB subform assay either alone or in combination with a Tn. At 6 h, sensitivity was highest (91%) for CK-MB subforms followed by myoglobin (78%) (107).

In a study of 190 ED patients with chest pain, Levitt and colleagues evaluated the use of CK-MB alone, myoglobin alone, or a combination of myoglobin and CK-MB at base-

Cardiac Markers in Chest Pain Evaluation

I 1 Myoglobin

TNT I I

TNI 1 I

LDH 1 1

Fig. 4. Overlapping time frames of markers.

Table 6

Predictive capabilities of serum enzymes in the ED

Table 6

Predictive capabilities of serum enzymes in the ED

Serum

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