Evaluation of bivalirudin hyper- and hypo-ACT responses in the setting of percutaneous coronary intervention

Bivalirudin has emerged as a suitable alternative anticoagulant to unfractionated heparin and low-molecular-weight heparins during percutaneous coronary intervention (PCI) procedures in the management of coronary artery disease and acute coronary syndromes (ACS). In clinical trials, bivalirudin dosing was standardized, and activated clotting time (ACT) did not influence dosing adjustments. The role of ACT monitoring of bivalirudin in PCI is not defined based on current practice guidelines.

The hypothesis of this study is that hyper- and hypo-ACT responses to bivalirudin in PCI may be associated with excessive bleeding or thrombotic complications.

The planned protocol screened all patients who received bivalirudin therapy and ACT monitoring during PCI in a single center's cardiac catheterization laboratory from July 2009 to June 2010. The first ACT monitored 5 to 60 minutes after bivalirudin initiation was screened for inclusion. Values above 800 seconds and below 300 seconds were included as hyper- and hypo-ACT responses, respectively. Outcomes assessed include thrombotic and bleeding complications.

There were 32 patients identified as hyper-responders and 20 patients identified as hypo-responders. There were no significant thrombotic or bleeding complications in the hyper-responder group. There was 1 case (1/20, 5%) of angiographically confirmed acute stent thrombosis immediately following the placement of 5 adjoining bare-metal stents in the right coronary artery of a hypo-responder.

Hyper-ACT responses to bivalirudin therapy in PCI were not associated with additional bleeding risk. Bivalirudin may not adequately protect hypo-ACT responders against thrombotic complications during PCI.