ACTIVATED CLOTTING TIME DIFFERENTIAL IS A SUPERIOR METHOD OF MONITORING ANTICOAGULATION FOLLOWING CORONARY ANGIOPLASTY

The standard high-range activated clotting time (sHR ACT) is used to m onitor anticoagulation postangioplasty (PTCA), but may be unreliable. We assessed the accuracy of a new method we termed the ACT differentia l (ACT Diff), obtained by measuring the difference between an sHR ACT and a heparinase ACT from the same sample, Heparinase removes heparin from its sample and provides a current heparin-free baseline, For phas e 1 of the study, the sHR ACT, ACI Diff, and laboratory APTT were meas ured in 250 samples from 75 PTCA patients. In 125 samples with an APTT prolonged but within measurement range, linear regression against the APTT was performed. The correlation coefficient was 0.74 for the ACT Diff and 0.24 for the sHR ACT. An ACT Diff of 15-25 sec was found to e qual an APTT of 2.5-3.5 x control. In 50 samples with a normal activat ed partial thromboplastin time (APT), there was good differentiation b y the ACT Diff of results from those adequately heparinized, with a va lue of 0.9 +/- 4.4 sec. The sHR ACI was 114 +/- 15.5 sec, and could no t reliably distinguish between anticoagulated and nonanticoagulated sa mples. In 75 samples obtained with a high APTT (above measurement rang e), the ACT Diff was >30 sec in 95% of samples, and again this allowed differentiation from therapeutic samples. The equivalent sHR ACI was 148 sec, and could not reliably distinguish between anticoagulated and overanticoagulated samples as the ACT Diff could, in phase 2, to exam ine the clinical usefulness of the ACI Diff, 286 patients were managed post-PICA by starting heparin when ACT Diff fell to <50 sec, maintain ing ACT Diff at 15-25 sec during heparin infusions, and following cess ation of heparin, by removing sheaths when the ACT Diff was <7 sec, Th ese patients were compared to a control group of 250 patients. Major b leeding (5% vs. 0.5%, P < 0.005) and minor bleeding (30% vs. 13%, P < 0.001) were significantly reduced in the group managed using the ACT D iff, The reduction in bleeding was thought to be due to the rapid avai lability of reliable results, Abrupt closure was low in both groups (0 % with ACT Diff vs. 0.8%), No other thrombotic events occurred. Follow ing phases 1 and 2, the ACT Diff replaced the APTT in all PTCA patient s at this institution. In the 18 mo from July 1993, 1,104 patients wer e managed this way, Incidence of major bleeding (0.2%), transfusion re quirement (0.1%), false anneurysm (0.6%), and abrupt closure during he parin infusion (0.1%) remained low. In conclusion, the ACT Diff is mor e accurate than an sHR ACT, and its clinical use in PICA patients is a ssociated with a very low incidence of complications from anticoagulat ion. Its routine use should be considered by units unable to obtain ra pid APTT results. (C) 1996 Wiley-Liss, Inc.