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High platelet reactivity common in poorly-controlled diabetes

Reuters Health • The Doctor's Channel Daily Newscast

NEW YORK (Reuters Health) – An “important” relation exists between platelet reactivity and glycemic control in patients with type 2 diabetes and coronary artery disease who are on dual antiplatelet therapy, researchers report in the November issue of the American Heart Journal.

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.