Objectives. The purpose of this study was to determine whether a low procedural activated coagulation time is associated with a high rate of in hospital complications and to identify whether there is an activated coagulation time range that may be associated dth a low rate of complications. Background. In recent years the activated coagulation time has come into widespread use for monitoring anticoagulation in the catheterization laboratory. However, considerable controversy exists as to the standards by which to judge ''adequate'' anticoagulation for interventional procedures. Methods. From a total of 1,469 consecutive patients with percutaneous transluminal coronary angioplasty, we retrospectively identified 103 (Group I, 7% of the overall population) with major complications of death or emergency or urgent coronary artery bypass graft surgery and compared them with 400 patients without complications (Group II), Group I patients had more high risk clinical characteristics, such as type B and C lesions, class III and IV angina, recent myocardial infarction and recent thrombo lytic treatment. Activated coagulation times were compared between Groups I and II at baseline, after administration of 10,000 U of heparin and at the end of the procedure. Results. There were no differences in baseline activated coagulation times between Groups I and II. Group I had significantly lower activated coagulation times after heparin therapy and at the end of the procedure: 61% <250 s, 20% between 250 and 275 s, 11% between 275 and 300 s and 8% >300 s; 279 of Group II had activated coagulation times 27% <250 s, 17% between 250 and 275 s, 35% between 275 and 300 s and 21% >300 s (p < 0.0001), Complications occurred in all patients with final activated coagulation times <250 s but in only 0.3% of patients with final activated coagulation times >300 s. Conclusions. A diminished activated coagulation time response to an initial bolus of heparin is associated with major in-hospital complications after coronary angioplasty, although patients with complications did have a higher risk before the procedure. It remains to be determined whether there is an ideal ''target'' activated coagulation time for interventional procedures.
