Antithrombin activity during the period of percutaneous coronary revascularization - Relation to heparin use, thrombotic complications and restenosis

OBJECTIVES This study evaluated changes in antithrombin (AT) activity around the time of percutaneous transluminal coronary revascularization (PTCR) with unfractionated heparin anticoagulation and the effects these changes had on major thrombotic complications of PTCR. BACKGROUND Heparin is used during PTCR to prevent thrombosis. However, heparin, a cofactor for AT, causes AT activity to fall. AT activity <70% is associated with thrombosis. There is a prothrombotic state after heparin discontinuation that has not been well explained. METHODS Antithrombin activity was sampled at the start and end of PTCR and the next two mornings in 250 consecutive patients. We recorded occurrence of major thrombotic events, defined as 1) major thrombotic complications of PTCR; 2) major in-lab thrombus formation; or 3) subacute occlusion. Discriminant analysis was employed to evaluate the relationship of AT activity to these events. Change in AT activity;and its relationship to heparin was evaluated. Evidence of restenosis at six months was obtained. RESULTS There were 14 major thrombotic events. Antithrombin activity <70%, was strongly (p = 0.006) associated with these events. The AT activity fell significantly through the morning after PTC-R when 21% of patients had AT activity < 70%; AT activity did not normalize until >20 h after heparin discontinuation. Pre-PTCR use of heparin led to lower AT activity in proportion to duration of heparin use. There was no relationship between;AT activity and restenosis. CONCLUSIONS Low AT activity may contribute to major thrombotic complications of PTCR. The way heparin is used before and after PTCR is important to development of low AT activity. (C) 1999 by the American College of Cardiology.