Conventional antithrombotic approaches.

Thrombus formation during percutaneous transluminal coronary angioplasty (PTCA) markedly increases the risk of abrupt closure, procedural failure, and major complications. Pretreatment with heparin may be beneficial in preventing procedural complications, although strategies for ensuring that patients have adequate anticoagulation have been the focus of considerable debate. Several studies have suggested a relationship between the development of PTCA complications and a low activated clotting time (ACT) or a low increase in ACT in response to heparin. Although there have been no prospective studies showing the superiority of any given threshold ACT over any other, current data support a recommendation that anticoagulation for patients undergoing PTCA be titrated to a HemoTec ACT of greater than 275 to 300 seconds or to a Hemochron ACT of greater than 350 to 400 seconds. Adjusting the heparin bolus dose according to body weight does not achieve a more predictable level of anticoagulation, although it may help avoid excessive anticoagulation in lighter-weight patients.