CONTEXT: Controversy surrounds the diagnostic and prognostic importance of
slightly elevated cardiac markers in patients with acute coronary
syndromes without ST-segment elevation. OBJECTIVES: To investigate the
relationship between peak creatine kinase (CK)-MB level and outcome and to
determine whether a threshold CK-MB level exists below which risk is not
increased. DESIGN AND SETTING: Retrospective observational analysis of
data from the international Platelet Glycoprotein IIb/IIIa in Unstable
Angina: Receptor Suppression Using Integrilin Therapy (PURSUIT) trial,
conducted from November 1995 to January 1997. PATIENTS: A total of 8250
patients with acute coronary syndromes without ST-segment elevation who
had at least 1 CK-MB sample collected during their index hospitalization.
MAIN OUTCOME MEASURE: Mortality at 30 days and 6 months, was assessed by
category of index-hospitalization peak CK-MB level (0-1, >1-2, >2-3, >3-5,
>5-10, or >10 times the upper limit of normal). Multivariable logistic
regression was used to determine the independent prognostic significance
of peak CK-MB level after adjustment for baseline predictors of 30-day and
6-month mortality. RESULTS: Mortality at 30 days and 6 months increased
from 1.8% and 4.0%, respectively, in patients with normal peak CK-MB
levels, to 3.3% and 6.2 % at peak CK-MB levels 1 to 2 times normal, to
5.1% and 7.5% at peak CK-MB levels 3 to 5 times normal, and to 8.3% and
11.0% at peak CK-MB levels greater than 10 times normal. Log-transformed
peak CK-MB levels were predictive of adjusted 30-day and 6-month mortality
(P<.001 for both). CONCLUSIONS: Our data show that elevation of CK-MB
level is strongly related to mortality in patients with acute coronary
syndromes without ST-segment elevation, and that the increased risk begins
with CK-MB levels just above normal. In the appropriate clinical context,
even minor CK-MB elevations should be considered indicative of myocardial
infarction