Adverse Prognostic Significance of Thrombocytopenia in Acute Coronary Syndrome

Abstract

In this issue of Circulation , Wang and colleagues1 demonstrate that even mild thrombocytopenia (platelet count nadir <150×109/L) developing in patients with acute coronary syndrome (ACS) is associated with bleeding and death. Similar observations have been made in other settings. Critically ill patients with thrombocytopenia have increased duration of mechanical ventilation and risk of death.2 An increased risk of death also has been reported in thrombocytopenic patients (platelet count nadir <100×109/L) with non–ST-segment elevation ACS (odds ratio [OR], 6.7; 95% confidence interval [CI], 1.9 to 25; P =0.003).3 Patients receiving heparin in diverse clinical settings who develop thrombocytopenia also have an increased risk of death (OR, 3.4; 95% CI, 2.1 to 5.6; P <0.001); the risk is highest in patients with the greatest decrease in platelet count.4 Article see p 2454 Why should the development of thrombocytopenia predict mortality? In sepsis, thrombocytopenia reflects prohemostatic mechanisms (eg, thrombin-mediated platelet activation) and proinflammatory stimuli (eg, enhanced platelet clearance by macrophages).5 Logically, the more pronounced the septic stimuli are, the greater the risks for death and for thrombocytopenia are. But why should thrombocytopenia predict for greater mortality in cardiovascular disease? Perhaps baseline (preadmission) low-normal platelet count values—an important predisposing factor to subsequent in-hospital thrombocytopenia1—reflect a greater burden of atherosclerosis, aortic stenosis, or other vascular pathologies that predispose to heightened platelet consumption. Alternatively, right-sided heart failure (associated with hepatic congestion and resultant hypersplenism) could predispose to low baseline platelet count levels. In these situations, any event that further enhances platelet destruction or reduces platelet production is likely to lead to thrombocytopenia. Wang and colleagues found that specific pharmacological agents infrequently triggered or exacerbated thrombocytopenia. Of course, exceptions exist to the general rule that thrombocytopenia is due to factors other than drug therapy. Those …