Objectives: The study investigated the relationship among creatine kinase (CK) elevations, clinical characteristics and cardiac events across the whole spectrum of acute coronary syndromes (ACS).
Background: Elevated serum levels of cardiac enzymes have been shown to be a major prognostic determinant in acute myocardial ischemia. Yet prior to this report, the relation between cardiac enzyme levels and other prognostic determinants across the entire spectrum of ACS has not been explored by a large clinical study.
Methods: We evaluated the relation between the maximum CK ratio (CK level/upper limit of normal) in the early hours following admission and cardiac events at six months in 11,725 patients enrolled in a large trial of ACS.
Results: Patients with higher risk characteristics, such as older age, female gender, hypertension, diabetes, prior coronary events or heart failure, more frequently presented without ST-segment elevation on the electrocardiogram and tended to develop lesser enzyme elevations. After adjusting for significant baseline predictors of cardiac events, a continuous correlation was observed between the CK ratio and death (chi-square 63.04, p < 0.0001) and (re)infarction or death (chi-square 55.48, p < 0.0001). This correlation was similar for patients with and without ST-segment elevation. The adjusted incidence of cardiac events at follow-up began to rise even for CK levels within the normal range, the steepest part of the curve residing between one and three times the upper limit of normal. In patients with a CK ratio of >1 to 2 compared with those within the normal range, the adjusted odds ratio for death was 1.26 (95% confidence interval [CI] 0.98 to 1.63), and 1.59 (95% CI 1.38 to 1.90) for (re)infarction and death. For all CK levels, the event rate was higher among patients without ST-segment elevation.
Conclusions: Although high-risk patients with ACS often develop lesser CK elevations, this study demonstrated that even minor enzyme elevations appear to have important and independent prognostic implications.