ACT May Be Useful In Point-Of-Care Monitoring Of Enoxaprin Anticoagulation Effect In Patients Undergoing PTCA

Intravenous enoxaparin has been found to increase activated clotting time (ACT) at 5 minutes in patients undergoing percutaneous coronary intervention (PCI), indicating that ACT may be useful in monitoring anticoagulation.

Enoxaparin has been used successfully in patients undergoing PCI, and offers several advantages over unfractionated heparin, including greater bioavailability, a decreased incidence of thrombocytopaenia, resistance to inactivation by platelet factor 4, and less activation of platelets.

However, a perceived limitation of enoxaparin therapy is the lack of a rapid point-of-care test to assess the anticoagulant effect.

Because most laboratories can measure ACTs and operators are familiar with their interpretation, Mark Lawrence, DO, and colleagues of Scott and White Memorial Hospital in Temple, Texas, United States, conducted a study to determine if the ACT could detect the effect of intravenous enoxaparin in the setting of PCI.

The study population consisted of 67 consecutive patients undergoing PCI, treated with either 0.75 mg/kg intravenous enoxaparin and concomitant eptifibatide or 1 mg/kg enoxaparin without eptifibatide.

ACTs were measured at baseline and 5 minutes following enoxaparin administration with a Hemochron device (International Technidyne, Edison, NJ) using arterial blood from the femoral sheath. In 26 patients, blood samples were also collected for the Rapidpoint Coag Enoxaparin test card (ENOX; PharmaNetics, Morrisville, NC), a new point-of-care test released during the study.

Analysis showed that after 0.75 mg/kg of enoxaparin plus eptifibatide, mean ACT increased from 125 ± 22 to 194 ± 24 seconds. Comparatively, ACT increased from 122 ± 22 to 199 ± 20 seconds after 1 mg/kg of enoxaparin.

The mean increase in ACT was 69 ± 23 seconds in the 0.75 mg/kg group (n = 45; P < .0001) and 77 ± 26 seconds in the 1 mg/kg group (n = 22; P < .0001). Additionally, a strong linear relationship was observed between ACT and ENOX values (r = 0.86; P < .0001). No patient developed transient abrupt closure, thrombus formation, major bleeding, or required urgent revascularisation. The investigators say that point-of-care monitoring with either ACT or ENOX coagulation time has several potential advantages. “It may help confirm adequate anticoagulation in patients receiving an earlier subcutaneous dose of enoxaparin,” they note. “Furthermore, it could identify the presence or lack of a therapeutic effect in patients with morbid obesity, renal insufficiency, and in those receiving enoxaparin with brinolytic therapy, or smaller i.v. doses of enoxaparin.”