Lack of association between factor V Leiden and thromboembolism in patients with prosthetic heart valves.

Thromboembolism represents the most serious complication in patients with prosthetic heart valves, and causes significant mortality and morbidity. Many risk factors for the condition have been identified. However, many patients who have a therapeutic level of anticoagulation and no obvious risk factors develop thromboembolism. Factor V Leiden, found in 3-7% of the normal population, is the most common inherited factor associated with thrombosis. Whether or not this factor is associated with thromboembolism in this setting has not been explored. This study compares the prevalence of factor V Leiden in patients with prosthetic heart valves, with and without thromboembolic complications. A total of 148 patients were studied. Thirty had documented thromboembolic complications and none exhibited the factor V mutation. Of the 118 patients without thromboembolic complications, seven (5.9%) were heterozygous for factor V Leiden (P = 0.345, by Fisher's two-tailed exact test; odds ratio 0, 95% confidence interval 0.0-4.34). We conclude that until future data shows otherwise, routine testing for factor V Leiden in patients with prosthetic heart valves is not warranted, except as part of ongoing research.