Activated protein C resistance, factor V Leiden, and central retinal vein occlusion in young adults.

OBJECTIVE: To confirm the relationship between resistance to activated protein C (APC), factor V Leiden, and central retinal vein occlusion in young adults as reported in a recent study of patients younger than 50 years. PATIENTS AND METHODS: Patients younger than 50 years with central retinal vein occlusion were identified from the medical records of the Wills Eye Hospital Retina and Retina Vascular Services. Blood samples were taken from each patient and analyzed for resistance to APC and identification of factor V Leiden. RESULTS: Only 1 (4.7%) of 21 patients evidenced resistance to APC and the presence of factor V Leiden. This patient was also the only one to report a family history of thrombotic disease. CONCLUSIONS: We were unable to confirm the high percentage of resistance to ACP among young adult patients with central retinal vein occlusion. The finding of resistance to APC in only 1 (4.7%) of 21 patients is similar to that found in the general population.

Prevalence of heparin-associated antibodies without thrombosis in patients undergoing cardiopulmonary bypass surgery.

BACKGROUND: Patients with cardiovascular disease almost invariably receive heparin before cardiopulmonary bypass surgery, which places them at risk of developing heparin-associated antibodies with a risk of thromboembolic complications. This study was designed to determine the prevalence of heparin-induced antibodies in patients before and after cardiopulmonary bypass surgery. METHODS AND RESULTS: Plasma from 111 patients was tested before surgery and 5 days after surgery for heparin-dependent platelet-reactive antibodies with a 14C-serotonin-release assay (SRA) and for antibodies to heparin/platelet factor 4 complexes with an ELISA. Heparin exposure after surgery was minimized. Heparin-dependent antibodies were detected before surgery in 5% of patients with SRA and 19% of patients with ELISA. By the fifth postoperative day, there was a marked increase in patients positive on the SRA or ELISA (13% and 51%, respectively; P < .01 for each). Patients who had received heparin therapy earlier in their hospitalization were more likely to have a positive ELISA before surgery (35%; P = .017) and a positive ELISA (68%; P = .054) or SRA (30%; P = .002) after surgery. However, there was no difference in the prevalence of thrombocytopenia or thromboembolic events between the antibody-positive and-negative groups. CONCLUSIONS: Approximately one fifth of patients undergoing cardiopulmonary bypass surgery have heparin-induced platelet antibodies detectable before the procedure as a result of prior heparin exposure, and many more develop antibodies after surgery. The absence of an association between these antibodies and thromboembolic complications in this study may be, in part, attributable to careful avoidance of heparin after surgery. The high prevalence of heparin-induced antibodies in this setting suggests that these patients may be at risk of developing thrombotic complications with additional heparin exposure.