Preoperative anti-PF4/heparin antibody level predicts adverse outcome after cardiac surgery

Objective: Preexisting serum antibodies to heparin/platelet factor 4 complexes may predispose adult cardiac surgical patients to increased perioperative morbidity and mortality. We sought to determine the association between preoperative serum antibodies directed against platelet factor 4/heparin complexes and major complications (in-hospital death or length of stay > 10 days) in adult cardiac surgical patients. Methods: In a prospective observational study of 466 patients undergoing elective coronary artery bypass grafting, valvular heart surgery, or both, preoperative serum was assayed for anti-platelet factor 4/heparin antibody by using a commercially available enzyme-linked immunosorbent assay (Asserachrom HPIA). Known preoperative risk factors were assessed, and patients were assigned a risk score by using the validated method of Parsonnet and colleagues. Results: Major complications (death or postoperative hospitalization > 10 days) occurred in 108 patients (23%). Overall, 59 (13%) patients had a positive preoperative anti-platelet factor 4/heparin antibody screen (upper limit of normal is 0.5 optical density units). A positive assay result independently predicted an increased risk of major complications (P = .0284; odds ratio, 1.98; 95% confidence interval, 1.06 - 3.62) over and above the effect of the Parsonnet risk score (P < .001; odds ratio, 1.07; 95% confidence interval, 1.05 - 1.10). The level of preoperative antiplatelet factor 4/heparin antibody was also significantly associated with major complications (P = .036; odds ratio, 1.31; 95% confidence interval, 1.02 - 1.68) independently of the Parsonnet risk score. No association (P > .75) existed between the Parsonnet risk score and preoperative anti-platelet factor 4/heparin antibody level. Conclusions: Serum antibodies directed against platelet factor 4/heparin complexes are prevalent in the adult patient population undergoing cardiac surgery. The presence of these antibodies before surgery is an independent predictor for death or prolonged hospitalization after adult cardiac surgery.