The role of heparin-associated antiplatelet antibodies in the outcome of arterial reconstruction

Purpose: This study was designed to determine the incidence rate of heparin -associated antiplatelet antibodies (HAAb) in patients who require major va scular reconstruction and to determine whether the HAAb were associated wit h perioperative thrombotic events. Methods: One hundred six patients who underwent elective arterial reconstru ction for cerebrovascular occlusive disease (n = 48), aortoiliac occlusive disease (n = 13), aortoiliac aneurysm (n = 17), mesenteric arterial occlusi ve disease (n = 1), or infrainguinal arterial occlusive disease (n = 28) pr ospectively underwent evaluation from July 1, 1996, to Tune 30, 1997. Hepar in-associated antibody tests (with a two-point platelet aggregation assay) and platelet counts (via Coulter counter) were performed before surgery and on or after the 4th day after vascular reconstruction. Arterial reconstruc tion thromboses were established by means of duplex ultrasound scanning or angiography. Acute myocardial infarction (AMI) and venous thromboses were d iagnosed with clinical criteria and duplex ultrasound scanning, respectivel y. A significant decrease in platelet count was defined as a platelet count of less than 100,000/mm(3) or as a more than 30% drop in the platelet coun t. Results: Twenty-two patients (21%) had at least one positive HAAb assay: on e assay was positive before surgery only (after angiography), six were posi tive both before and after surgery, and 15 were positive after surgery only . There were three perioperative deaths-one in the HAAb-positive group and two in the HAAb-negative group. Ten thrombotic events occurred in the perio perative period. Four thrombotic events (three operative site thromboses an d one AMT) occurred in the HAAb-positive group (18.2%). All of these patien ts were undergoing heparin therapy. Of the six patients (with three operati ve site thromboses, two deep venous thromboses, and one AMI) in the HAAb-ne gative group (7%; P = .21), three were undergoing heparin therapy. No patie nt who was HAAb positive with a thrombotic event had thrombocytopenia or a significant decrease in platelet count. Conclusion: The frequent exposure to heparin by patients with peripheral va scular disease is associated with a high incidence rate (21%) of HAAb forma tion, which makes it one of the more common hypercoagulable conditions in t hese patients. The patients who were HAAb positive had a 2.6-fold increase in perioperative thrombotic events. Thrombocytopenia or decreasing platelet counts were not reliable clinical markers for identifying patients who wer e HAAb positive. It is suggested that all patients who have undergone hepar in therapy and who have an unexplained perioperative thrombotic event devel op should undergo testing for HAAb.