Correlation Between Activated Clotting Time and Activated Partial Thromboplastin Time During Endovascular Treatment of Cerebral Aneurysms

Purpose: Endovascular treatment (EVT) of intracranial aneurysms (IAs) requires continuous anticoagulation to avoid thromboembolic complications. To monitor the anticoagulation, different tests may be used, including the activated clotting time (ACT) and the activated partial thromboplastin time (APTT). The aim of this study was to compare ACT and APTT for the monitoring of anticoagulation during EVT of IAs. Methods: Patients referred for EVT of an IA were included. After induction, baseline ACT and APTT were recorded, followed by a bolus infusion of unfractionated heparin (50 UI kg(-1)). The same tests were controlled 5 minutes later with the purpose of doubling the baseline ACT value. Correlation and agreement between both tests were evaluated for the percentage of change after the bolus. Multiple linear regressions were also calculated to show confounding factors. Complications and outcomes were also recorded. Results: Forty-five patients were checked for enrollment, and 24 were included for analysis. Mean (SD) percent variation for APTT was 432.1 (75.7) and 60.6 (23.0) for ACT, with P < 0.0001. With the Bland-Altman method, value of bias (SD) is 372 ( 86), with 95% limits of agreement ranging from 203 to 540. Pearson correlation for percent variation shows r (95% confidence interval) = -0.23 (-0.58 to 0.19), with P = 0.29 and R-2 = 0.05. One hundred percent of the APTT values could be defined as excessive anticoagulation by opposition of the 8% obtained with ACT. Conclusions: This prospective observational study shows that the ACT test is not well correlated with APTT and leads to a systematic excessive coagulation during EVT of IAs.