Is Warfarin Bridging Therapy Always Necessary?
Abstract & Commentary
By Michael H. Crawford, MD
Source: Annala AP, et al. Safety of diagnostic coronary angiography during uninterrupted therapeutic warfarin treatment. Am J Cardiol. 2008;102:386-390.
The management of anticoagulation in patients requiring long-term warfarin therapy is often problematic when they need cardiac catheterization. The usual recommendation is to hold warfarin until the INR is < 1.8 and cover the patient with bridging heparin therapy. However, this management strategy has not been fully studied. Thus, Annala et al from Finland assessed the databases of three hospitals in Western Finland and analyzed all patients on warfarin undergoing cardiac catheterization. They were compared to a matched control group not on warfarin. All three hospitals used the same arterial catheterization protocols, and immediate sheath removal was the norm. Long-term warfarin therapy in the 258 patients analyzed was largely for atrial fibrillation (73%), prior stroke (7%), and mechanical valve (6%). Catheterization was performed on uninterrupted warfarin therapy in 178 patients (69%), 22 of whom also received heparin because of a supratherapeutic INR or unstable angina. In 80 patients (31%), catheterization was done with a warfarin pause, and 24 of these patients had heparin bridging. A heparin bolus during the procedure was given to 20% of the 80 warfarin pause patients. INR in those with uninterrupted warfarin therapy was 2.3 vs 1.9 in the others. Access site complications occurred in 1.7% of those on uninterrupted warfarin vs 0% in warfarin pause on no bridge therapy and in 8.3 % with bridging therapy. The two major bleeds occurred in bridge therapy patients. Supratherapeutic INR (> 3.0) was associated with more access site complications (9.1%) vs 1.5% for therapeutic and 1.0% for subtherapeutic INR (< 2.0). Annala et al concluded that performing cardiac catheterization during warfarin therapy is a viable alternative to heparin-bridging therapy.
Commentary
This analysis of a relatively large group of patients undergoing coronary angiography who required long-term anticoagulation with warfarin exhibits two causes of an increased risk of bleeding complications: a supratherapeutic INR (> 3.0) and heparin bridging therapy. The former is obvious, but the latter is more complicated. There are several potential reasons for increased bleeding with bridge therapy. First, all anticoagulants increase the risk of bleeding, so putting people on two is an additional risk even though the warfarin is held. In this study, the INR on bridging therapy was 1.9 vs 2.3 on uninterrupted warfarin; not a great difference. Heparin may cause bleeding in ways not captured by the INR. Second, many of the bridged patients got low molecular weight heparin (LMWH), which has been shown in some studies to increase bleeding. In this study, access complications were 8.3% in those bridged with LMWH. Third, switching from one anticoagulant to another may increase bleeding. In the SYNERGY study, increased bleeding was noted in those who were switched from one anticoagulant to another by trial design.
Based on their analysis, Annala et al suggest that just doing catheterization on warfarin may be the best approach, especially if the INR is therapeutic. Most of their patients had femoral sticks. It could be argued that this recommendation would be even more cogent if a radial approach is used where hemostasis is easier to accomplish and monitor. Another approach discussed is to let the INR drift to 1.5-2.0 before the procedure. This was tried in a prior CABG study and found to be safe and efficacious. In this study, three-quarters of the patients were on warfarin for atrial fibrillation, and only 6% had mechanical valves. It could be argued that this lower INR approach would be safer in atrial fibrillation patients as compared to mechanical valve patients (higher risk of devastating thrombosis). Thus, decisions on what approach to take may have to be risk adjusted for the individual patient's indication for warfarin.
This study is limited by being retrospective and observational. Although it is relatively large for these kinds of studies, a relatively similar protocol for doing coronary angiography was used in the three hospitals. Finally, it should be pointed out that there are antidotes for warfarin therapy and unfractionated heparin, but none for LMWH. Thus, one should consider doing coronary angiography on uninterrupted warfarin therapy at therapeutic or slightly lower than therapeutic INRs (depending on the indication for warfarin) by the radial approach, if possible, and with unfractionated heparin for any perceived need for more anticoagulation (eg, unstable angina).
The management of anticoagulation in patients requiring long-term warfarin therapy is often problematic when they need cardiac catheterization.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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