Preexisting antibodies to platelet factor 4-heparin complexes in patients with acute coronary syndrome who have no history of heparin exposure.

Preexisting heparin-induced thrombocytopenia (HIT) antibodies are detected in some patients who have not previously been exposed to any kind of heparin. However, the role of preexisting HIT antibodies in acute coronary syndrome (ACS) is still unknown. This study was carried out to clarify the role of preexisting HIT antibodies in patients with ACS. Forty patients with ACS who had not been exposed to any kind of heparin via the venous or subcutaneous route or heparin-coated materials and had undergone percutaneous coronary intervention (PCI) under heparin anticoagulation within 6 h from the onset of ACS were chosen from the medical records in the cardiac emergency department. As a control of the ACS patients, 51 patients with angina pectoris who underwent elective PCI under heparin anticoagulation were chosen in the same manner as the ACS patients. Preexisting HIT antibodies were detected by ELISA in 6 patients. Two of the 6 patients developed HIT and 1 patient experienced thrombosis requiring intracoronary thrombolytic therapy. Thrombotic complications during and immediately after PCI in the very early stage after heparin administration were found in 4 of 6 patients with preexisting HIT antibodies. The frequency of preexisting HIT antibodies in ACS patients was significantly increased in comparison with that in non-ACS patients. The odds ratio of the risk of thrombotic complication between ACS and non-ACS patients was estimated at 8.82 (95% CI: 1.3-63). Also, preexisting HIT antibodies in ACS patients significantly increased the risk of thrombotic complications compared with ACS without preexisting HIT antibodies. In conclusion, ACS patients with positive HIT antibodies have an increased risk of thrombotic complications during PCI performed under anticoagulation with heparin.