In Vitro Assessment of von Willebrand Factor in Cryoprecipitate, Antihemophilic Factor/VWF Complex (Human), and Recombinant von Willebrand Factor

Patients with von Willebrand disease (VWD) often require treatment with supplemental von Willebrand factor (VWF) prior to procedures or to treat bleeding. Commercial VWF concentrates and more recently recombinant human VWF (rVWF) have replaced cryoprecipitate as the mainstay of therapy. In comparison with cryoprecipitate, the VWF content and multimer distribution under current manufacturing processes of these commercial products has not been reported. We measured the factor VIII (FVIII:C), VWF antigen (VWF:Ag), VWF collagen-binding activity (VWF:CB), VWF platelet-binding activity by GPIbM enzyme-linked immunosorbent assay (VWF:GPIbM), and percentage of high-molecular-weight (HMWM) VWF in 3 pools of group A and O cryoprecipitate, 3 vials of VWF concentrate (Humate-P), and 1 lot of rVWF (Vonvendi). We found that both group O and group A cryoprecipitate have significantly higher ratios of VWF:GPIbM activity and FVIII:C activity relative to VWF:Ag and have better preservation of HMWM than Humate-P. Although not compared statistically, rVWF appears to have more HMWM VWF and a higher ratio of VWF:GPIbM to VWF:Ag than Humate-P and cryoprecipitate. The estimated acquisition cost for our hospital for treating one major bleeding episode was more than 4-fold higher with Humate-P and 7- to 10-fold higher with rVWF than with cryoprecipitate.

Anticoagulation for Prosthetic Valves

Implantation of prosthetic valve requires consideration for anticoagulation. The current guideline recommends warfarin on all mechanical valves. Dabigatran is the new generation anticoagulation medication which is taken orally and does not require frequent monitoring. This drug is approved for treatment for atrial fibrillation and venous thromboembolism, but the latest large trial showed that this drug increases adverse events when used for mechanical valve anticoagulation. On-X valve is the new generation mechanical valve which is considered to require less anticoagulation due to its flow dynamics. The latest study showed that lower anticoagulation level lowers the incidence of bleeding, while the risk of thromboembolism and thrombosis remained the same. Anticoagulation poses dilemma in cases such as pregnancy and major bleeding event. During pregnancy, warfarin can be continued throughout pregnancy and switched to heparin derivative during 6–12 weeks and >36 weeks of gestation. Warfarin can be safely started after 1-2 weeks of discontinuation following major bleeding episode.

Hereditary Hypodysfibrinogenemia with Defective Release of Fibrinogenopeptide A (Fibrinogen Freiburg)

A new autoaomally inherited hypodysfibrinogenemia was recognized in four members in three different generations of a family. Only one patient had a major bleeding episode after trauma, the other affected members had no history of excessive bleeding or thromboembolic disease.The thrombin time and Reptilase time of plasma were greatly prolonged and partially corrected by the addition of calcium. Patient plasma prolonged the thrombin time of normal plasma. Fibrinogen levels ranged between 10 to 20 mg/100ml when measured as thrombin-clottable protein, whereas immunologically the fibrinogen levels were only slightly reduced.Functionally the major defect was impaired release of fibrinogenopeptide A upon incubation of the purified abnormal fibrinogen (94% clottable protein) with thrombin and Reptilase. The abnormal fibrinogen showed a delayed polymerisation of its purified fibrin monomers. The described abnormal fibrinogen was indistinguishable from normal fibrinogen by polyacrylamide gel electrophoresis with and without sodium dodecyl sulfate.