Association of Level of Kidney Function and Platelet Aggregation in Acute Myocardial Infarction

Background: Decreased kidney function has been established as an important risk factor in patients presenting with acute coronary syndrome. In acute coronary syndrome, increased platelet aggregation is associated with vascular complications. The aim of this study is to examine whether decreased kidney function is associated with altered platelet function in patients presenting with acute myocardial infarction. Study Design: Prospective cohort. Setting & Participants: 413 patients presenting with acute myocardial infarction admitted to the cardiac intensive care unit at Ostersund Hospital, Ostersund, Sweden. Predictors: Glomerular filtration rate less than 60 mL/min/1.73 m(2) estimated from serum cystatin C level, comorbidity, medications, and markers of inflammation and hemostasis. Outcomes & Measurements: Platelet aggregation was assessed by measuring the formation of small platelet aggregates (SPAs) by using a laser light scattering method. A greater SPA level indicates greater platelet aggregation. Platelet aggregation analysis was performed on days 1, 2, 3, and 5 in-hospital. Results: We observed a significant increase in platelet aggregation during the first 3 days in the hospital regardless of kidney function (P < 0.001). Platelet aggregation was more pronounced in patients with estimated glomerular filtration rate less than 60 mL/min/1.73 m(2) on day 2 (SPA count, 65,000 versus 47,000; P = 0.01) and day 3 (SPA count, 77,000 versus 52,000; P = 0.02). In a multiple linear regression analysis, decreased kidney function was no longer significantly associated with increased platelet aggregation. Older age, greater plasma fibrinogen level, and diabetes mellitus were associated with increased platelet aggregation in the multivariable model. Limitations: During the study period, 78 patients presenting with acute myocardial infarction were not eligible for inclusion. Differences in treatment with antiplatelet medication between the 2 groups might have affected our findings. Conclusions: Platelet aggregation increases during the first days after acute myocardial infarction regardless of kidney function. There is no difference in platelet aggregation in patients according to level of kidney function. Am J Kidney Dis 54:262-269. (C) 2009 by the National Kidney Foundation, Inc.