Activated clotting times and activated partial thromboplastin times in patients undergoing coronary angioplasty who receive bolus doses of heparin

Abstract

The accurate assessment of coagulation status is an important part of interventional procedures performed in the cardiac catheterization laboratory. While the traditional clinical means of assessing heparin anticoagulation has been with the activated partial thromboplastin time (APTT), the activated coagulation time (ACT) has come into widespread use in the catheterization laboratory as an assay of whole blood clotting time which can be performed rapidly at the bedside. The purpose of the present study was to (1) assess the anticoagulant effect of a 10,000 U bolus of heparin in PTCA patients and (2) document the relationship between ACTs and APTTs in a subset of these patients. Baseline and postheparin ACTs were measured using a HemoTec coagulation timer in 545 unselected PTCA patients. The average baseline ACT was 120 +/- 22 sec. After a 10,000 U bolus of heparin the average ACT was 249 +/- 44 sec; 58% of patients had an ACT less than 250 sec, 17% had an ACT between 250 and 275 sec, 12% had an ACT between 275 and 300 sec, and 13% had an ACT greater than 300 sec. A total of 175 paired ACT and APTT measurements were obtained in a random subset of these patients at baseline, after heparinization, and at 4-6 hr intervals after the procedure. The APTT was limited by absolute upper and lower limits of 150 and 22 sec; there were no such limits on the ACT. When limiting values were excluded, there was a strong overall correlation between ACT and APTT measurements (r = 0.92, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Coagulation Assays

“…10 The dose of heparin or bivalirudin required in these settings is beyond the range that can be measured with the aPTT. 16 Typically, whole blood is collected into a tube or cartridge containing a coagulation activator (eg, celite, kaolin, or glass particles) and a magnetic stir bar, and the time taken for the blood to clot is then measured. 10 The reference value for the ACT ranges between 70 and 180 seconds.…”

“…10 Thus, a less sensitive test of global anticoagulation such as the ACT is used to monitor the level of anticoagulation in patients undergoing percutaneous coronary interventions or aortocoronary bypass surgery. 16 Although several retrospective studies defined an inverse relationship between the likelihood of a thrombotic event and the ACT after heparin administration for percutaneous coronary intervention (PCI), 32,33 more recent data suggest that ischemic end points do not increase with decreasing ACT values, provided that the ACT is Ն200 seconds. 34 LMWH is derived from unfractionated heparin by chemical or enzymatic depolymerization.…”

ACC/AHA/SCAI Practice Guidelines, February 21, 2006

“…Although the intensity of anticoagulation with unfractionated heparin is generally determined with activated partial thromboplastin times, these values are less useful for monitoring anticoagulation during coronary angioplasty, because higher levels of anticoagulation are needed than can be discriminated with the activated partial thromboplastin time alone. Instead, the activated clotting time (ACT) has been more useful to follow heparin therapy during coronary angioplasty (725). The Hemochron and HemoTec devices are commonly used to measure ACT values during coronary angioplasty (725)(726)(727).…”

“…Instead, the activated clotting time (ACT) has been more useful to follow heparin therapy during coronary angioplasty (725). The Hemochron and HemoTec devices are commonly used to measure ACT values during coronary angioplasty (725)(726)(727). The Hemochron ACT generally exceeds the HemoTec ACT by 30 to 50 s, although considerable measurement variability exists.…”

Heparin dose during percutaneous coronary intervention: how low dare we go?

“…14 15 The activated partial thromboplastin time (aPTT) requires a specimen to be sent to the coagulation laboratory with an inevitable delay; unlike ACT, aPTT has limited accuracy when high or low concentrations of heparin are used. 16 The heparin management test (HMT) may provide a more representative bedside test than ACT. 17 18 Only a drop of blood is required and there appears to be a good correlation between ACT and HMT.…”