Protein Z levels and prognosis in patients with acute coronary syndromes

Background: Protein Z, a vitamin K-dependent glycoprotein, serves as a cofactor for the inhibition of activated coagulation factor X. During recent years, a role for low levels of protein Z in prothrombotic disorders such as ischemic stroke and acute coronary syndromes (ACS) has been reported. The aims of this study were to test changes in protein Z and their association with outcome at 1-year follow-up in 193 (150 male, 43 female) patients with ACS. Results: Protein Z plasma levels were significantly lower (p < 0.0001) after 1 year [1600 (28-3736) ng/mL] compared to the baseline [1695 (294-4068) ng/mL]. Regression analysis showed a significant association between baseline protein Z below the 5th percentile of our control group and subsequent adverse cardiac events at follow-up (odds ratio 3.3; 95% CI 1.04-10.7; p=0.04). Moreover, Cox regression analysis showed that low protein Z levels at admission were significant predictors of major adverse cardiac events (cardiac death, non-fatal recurrent myocardial infarction, and need for target lesion revascularization) after 1 year (hazard risk 2.5; 95% CI 1.02-6.5, p=0.04). Conclusions: Our results show that in patients with ACS: 1) protein Z decreases moving from the acute to the convalescent phase; and 2) low levels of baseline protein Z are significantly associated with adverse outcome at 1-year follow-up.