Plasma Levels of Nitrite/Nitrate and Platelet cGMP Levels Are Decreased in Patients With Atrial Fibrillation

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Abstract
Patients with atrial fibrillation have been reported to exhibit abnormal hemostasis. Since nitric oxide (NO) exerts antithrombotic effects and attenuates platelet function, we evaluated two indicators of plasma NO levels, the plasma levels of nitrite and nitrate (NOx), and the levels of cGMP in platelets. We also examined whether indicators of plasma NO levels were associated with abnormalities in parameters related to platelet function, blood coagulation, and fibrinolysis. We evaluated 45 patients with chronic sustained atrial fibrillation (33 men and 12 women, age range 63±2 years) compared with 45 sex- and age- (±2 years) matched nonhospitalized subjects with sinus rhythm. There were no significant differences between the two groups in the incidence of risk factors for stroke except for ischemic heart disease or in echocardiographic parameters. Plasma levels of NOx measured using the Greiss reagent (mean [interquartile range]: 15.6 [9.5 to 25.7] versus 24.1 [14.2 to 40.8] μmol/L, n=45) and the platelet cGMP levels (0.33 [0.16 to 0.67] versus 0.63 [0.31 to 1.29] pmol/10 9 platelets, n=9) were significantly ( P <.05) lower in the patients with atrial fibrillation than in the control subjects. Plasma levels of d -dimer, β-thromboglobulin, and fibrinogen were significantly ( P <.05) higher in the patients with atrial fibrillation. The two groups did not differ as to the plasma levels of tissue plasminogen activator or plasminogen activator inhibitor-1. Our findings suggest that a decrease in plasma NO levels may account for the hemostatic abnormalities observed in patients with atrial fibrillation.