Abnormalities in von Willebrand factor and antithrombin III after cardiopulmonary bypass operations for congenital heart disease.

In patients with congenital heart disease two poorly understood postoperative complications are pulmonary hypertensive crises after repair of large atrioventricular or ventricular septal defects and right atrial and pulmonary thrombi after the Fontan operation. In this study we assessed whether cardiopulmonary bypass in these patients is associated with the release of agents that might induce platelet aggregation and vasoconstriction, such as biologically active von Willebrand factor and platelet-activating factor. In addition, we measured levels of anticoagulants such as antithrombin III and proteins C and S. Three groups of patients with congenital heart disease undergoing cardiopulmonary bypass were monitored through the perioperative period for secundum atrial septal defects, large atrioventricular or ventricular septal defects, and tricuspid atresia or univentricular heart (Fontan candidates). Control values were obtained from age-matched patients; patients requiring major noncardiac operations and those with cardiac disease not requiring cardiopulmonary bypass were also studied. After cardiopulmonary bypass in all three groups biologic activity of von Willebrand factor increased markedly in the immediate and early postoperative periods compared with preoperative values, whereas antithrombin III values were decreased. Platelet-activating factor was detected in only two patients with congenital heart disease, both in the early postoperative period. In contrast, patients who did not have cardiopulmonary bypass did not show these abnormalities. All measured parameters normalized at late follow-up (6 to 18 months after operation). Although cardiopulmonary bypass in these patients resulted in increased von Willebrand factor activity and decreased antithrombin III, changes that may predispose the patient to platelet aggregation and thrombus formation, absolute values in individual patients alone were not predictive of pulmonary hypertensive crises or detectable thrombi. This suggests that these hematologic abnormalities may contribute to but are not by themselves a cause of morbidity in the early postoperative period. Moreover, the increased von Willebrand factor biologic activity seen postoperatively in patients with congenital heart disease suggests that use of synthetic vasopressin may be ineffective and potentially detrimental.