Background and Purpose--We wanted to investigate whether common prothrombotic mutations are more prevalent in patients with atrial fibrillation who have had a stroke than in healthy controls. We also wanted to assess whether early recurrent ischemic cerebrovascular events were more frequent among carriers of the factor V Leiden or the prothrombin gene mutations than among others.

Methods--We used a case-control design with 367 patients with acute ischemic stroke and atrial fibrillation (cases) and 482 healthy blood donors (controls). All mutations were detected with conventional polymerase-chain reaction protocols.

Results--The odds ratios for carriers of the factor V Leiden, prothrombin gene 20210GA, methylenetetrahydrofolate reductase 677CT, or platelet glycoprotein IIIa 1565TC (Pl^A2) mutation were 0.91, (95% CI, 0.51 to 1.59), 2.25 (95% CI, 0.61 to 8.90), 0.83 (0.61 to 1.13), and 0.79 (0.57 to 1.10), respectively. Early recurrent ischemic stroke and total recurrent ischemic cerebrovascular events were slightly more frequent among carriers of the factor V Leiden mutation than among noncarriers: odds ratio 1.45 (95% CI, 0.41 to 5.1), and 1.59 (0.61 to 4.1), respectively. None of the patients with recurrent ischemic cerebrovascular events had the prothrombin gene mutation.

Conclusion--These mutations are not important risk factors for thromboembolic stroke associated with atrial fibrillation. Carriers of the factor V Leiden mutation had a small, nonsignificantly higher risk of early recurrent ischemic cerebrovascular events.