Dr. Paul A. Gurbel of the Sinai Center for Thrombosis Research in Baltimore, Maryland told Reuters Health, “The more poorly controlled the diabetes, the higher the platelet reactivity. These data suggest a rationale for glycemic control in the diabetic in order to reduce thrombotic risk.”
Dr. Gurbel and his associates compared platelet aggregation in response to 5 and 20 µmol/L adenosine diphosphate (ADP) in 36 patients with type 2 diabetes and 35 non-diabetics undergoing elective stenting on aspirin and clopidogrel maintenance therapy.
They found that diabetic patients had higher ADP-induced platelet aggregation than nondiabetic patients. At 5 µmol/L, platelet aggregation was 45 in diabetic subjects versus 33 in nondiabetic subjects (p = 0.009). At 20 µmol/L, it was 52 versus 40 (p = 0.004).
The 20 diabetic patients with hemoglobin A1C at or above 7.0 g/dL had significantly higher 5 and 20 µmol/L ADP-induced platelet aggregation than the 16 diabetic patients with hemoglobin A1C < 7.0 g/dL (54 vs 34 and 62 vs 40, respectively; p < 0.001 for both).
For the study, the researchers defined high platelet reactivity as platelet aggregation greater than 46% in response to 5 µmol/L ADP or greater than 59% in response to 20 µmol/L ADP. “These cut points were based on a previous study linking them to risk for post-stenting ischemic events,” the authors note.
Using these predefined 5 and 20 µmol/L ADP-induced aggregation cut-points, 44% and 39% of diabetic patients had high platelet reactivity, respectively, compared to 11% and 3% of nondiabetic patients.
Among diabetic patients with HbA1C 7.0 or higher, the prevalence of high platelet reactivity was 65% and 60% compared to 19% and 13% among those with HbA1C < 7.
These findings “provide a pathophysiologic mechanism explaining increased cardiovascular risk in patients with diabetes,” the authors say. “It is interesting,” they add, “that when partitioning the diabetes mellitus group by HbA1C, the < 7% group numerically approximate(s) the results of the non-diabetes mellitus group."
Dr. Gurbel and colleagues conclude: “Poorly controlled type 2 diabetic patients with the greatest platelet reactivity may benefit most from more potent antiplatelet strategies in addition to aggressive antihyperglycemic treatment.”
Am Heart J 2009.