Variability of Activated Clotting Time by Site of Sample Draw during Percutaneous Coronary Intervention

Background
Inadequate or excessive anticoagulation during PCI is associated with procedural-related thrombotic and bleeding complications. Activated clotting time (ACT) is the standard method for monitoring heparin therapy during PCI. Observations at our institution suggested a substantial difference between ACT values drawn from varying arterial sites, prompting the current study.

Methods
99 patients undergoing elective or urgent PCI at our institution from May to October 2018 were enrolled in an IRB-approved single-center prospective cohort study. Simultaneous intra-procedural arterial blood samples were drawn from the access sheath and the coronary guide catheter in each patient. Mean differences between ACT samples were determined. Baseline clinical and procedural variables were analysed.

Results
The mean age was 67 years with 71% males. 93% of patients were on aspirin, 36% were diabetic, and 25% had at least CKD 3. The most common presentation was ACS (62%). Most cases used radial access (88%) and a 6 Fr sheath (95%). The mean total heparin dose was 7232 IU. The simultaneous mean guide and sheath ACTs were 327 s (SD 62.6) and 257 s (SD 44.4), respectively, with a mean difference of 70 seconds (p<0.001). Figure 1 shows the distribution of the difference between the guide and sheath ACTs. 90% of guide ACTs were higher than the sheath ACTs. Analysis stratified by baseline clinical factors did not predict differences in the ACT values.

Conclusions
The ACT value in patients undergoing PCI is significantly greater when assessed via the guide catheter versus the access sheath. This difference should be taken into account when managing anticoagulation during PCI.