Antithrombotic Therapy in Invasive Procedures

Posted by • May 31st, 2013

In this trial, patients receiving oral anticoagulation therapy who required pacemaker or defibrillator surgery were assigned to heparin bridging or continuation of warfarin. Patients receiving warfarin had a markedly lower risk of clinically significant device-pocket hematoma.  This latest review article in our Current Concepts series comes from Dr. Patrick Kamath, Dr. Todd Baron, and Dr. Robert McBane at Mayo Clinic.

The question of whether antithrombotic therapy should be suspended in a patient who will be undergoing an invasive procedure involves balancing the risk of postprocedural bleeding with continued treatment against the thrombotic risk with suspension of treatment and use of bridging anticoagulation therapy. In general, a patient undergoing a procedure that is associated with a low risk of bleeding (low-risk procedure) can safely continue antithrombotic therapy and should do so, particularly if the patient is at high risk for a thromboembolic event (high-risk patient). Conversely, a patient undergoing a high-risk procedure can temporarily discontinue antithrombotic agents safely if the patient is at low risk for a thromboembolic event (low-risk patient).

Clinical Pearls

• What is the CHADS2-VASc score? 

For patients with nonvalvular atrial fibrillation, important determinants of the risk of stroke include the CHADS2 score and, more recently, the CHA2DS2-VASc score, which includes cardiovascular atherosclerotic disease and female sex as additional risk factors. Scores on the CHADS2 range from 0 to 6, with higher scores indicating a greater risk of stroke; congestive heart failure, hypertension, diabetes, and an age of 75 years or older are each assigned 1 point, and prior stroke or transient ischemic attack is assigned 2 points. The CHA2DS2-VASc score reflects the risk of stroke among patients with atrial fibrillation who are not receiving anticoagulation therapy; values range from 0 to 9, with higher scores indicating greater risk.

• How does the risk of coronary stent thrombosis differ between bare-metal stents and drug-eluting stents? 

The risk of stent thrombosis differs between bare-metal stents and drug-eluting stents. The risk of thrombosis is highest within 6 weeks after the placement of a bare-metal stent and within 3 to 6 months after the placement of a drug-eluting stent; antiplatelet therapy is required for at least 1 month after placement of a bare-metal stent and for 1 year after placement of a drug-eluting stent. After acute coronary syndromes, continuation of dual antiplatelet therapy is recommended for up to 12 months in patients with bare-metal stents and for at least 12 months in patients with drug-eluting stents, unless the risk of bleeding is excessive.

Morning Report Questions

Q: What are the recommendations for elective procedures in patients with coronary-artery stents?   

A: Most patients receiving dual antiplatelet therapy have coronary-artery stents. For these patients, an elective procedure associated with a high risk of bleeding should be postponed, if possible, for at least 6 weeks after the placement of a bare-metal stent and for at least 6 months after the placement of a drug-eluting stent. Ideally, a high-risk procedure should be delayed until completion of dual antiplatelet therapy (at least 12 months after the placement of either a bare-metal or drug-eluting stent). If an elective high-risk procedure must be performed (Table S2 in the Supplementary Appendix) within 6 weeks after the placement of a bare-metal stent or within 6 months after the placement of a drug-eluting stent, dual antiplatelet therapy should be continued, if possible. Aspirin therapy should never be discontinued. For patients with coronary-artery stents who are undergoing a high-risk procedure more than 6 weeks after the placement of a bare-metal stent or more than 6 months after the placement of a drug-eluting stent, aspirin should be continued, with thienopyridine therapy temporarily discontinued at an appropriate interval before the procedure.

Q: When should antithrombotic therapy be initiated after an invasive procedure?   

A: In patients receiving bridging therapy, heparin at a therapeutic dose should be withheld for 48 hours after the procedure. If the risk of postprocedural bleeding is deemed acceptably low, full-dose anticoagulation therapy may be initiated after a shorter interval. Because achieving full anticoagulation after the reinstitution of warfarin therapy takes several days, it can be reinstituted the evening of the procedure unless there is a substantial risk of delayed bleeding or unless reoperation is anticipated. The authors recommend delaying the reinitiation of treatment with dabigatran, rivaroxaban, or apixaban for at least 48 hours after high-risk procedures because the full anticoagulatory effect occurs shortly after administration and there are no reliable reversal agents for these medications. Clopidogrel administered at maintenance doses has a delayed onset of action, and treatment can therefore be reinitiated within 24 hours after the procedure. Treatment with other antiplatelet agents, including aspirin, can be reinitiated within 24 hours. The authors recommend caution when reinitiating treatment with prasugrel or ticagrelor because of their rapid onset of action, potent antiplatelet inhibition, and the lack of agents to reverse their effects.

Table 4. Overview of Traditional and Newer Antithrombotic Agents.

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