From the Guidelines
The target INR for a patient on warfarin who is undergoing Coronary Artery Bypass Grafting (CABG) should be less than 1.5 at the time of surgery. Warfarin therapy should be discontinued approximately 5 days before the scheduled CABG procedure to allow the INR to normalize. During this preoperative period, patients with high thrombotic risk (such as those with mechanical heart valves or recent venous thromboembolism) may require bridging anticoagulation with intravenous unfractionated heparin or subcutaneous low molecular weight heparin. The INR should be checked the day before surgery to confirm it has decreased to the target level. If the INR remains elevated (>1.5) closer to surgery, vitamin K (1-2 mg orally or intravenously) may be administered to expedite normalization. This target is important because elevated INR levels increase the risk of perioperative bleeding complications, which can lead to increased transfusion requirements, surgical reexploration, and poorer outcomes. After CABG, warfarin can typically be resumed 24-48 hours postoperatively when hemostasis is adequate, with the target INR determined by the specific indication for anticoagulation, as recommended by guidelines such as those from the American College of Cardiology Foundation/American Heart Association 1.
Some key points to consider in managing anticoagulation in patients undergoing CABG include:
- The risk of thromboembolism and the need for anticoagulation should be balanced against the risk of bleeding complications 1.
- The use of bridging anticoagulation may be necessary in patients with high thrombotic risk, but its use should be carefully considered and monitored 1.
- The target INR for patients on warfarin undergoing CABG may vary depending on the specific clinical context and the presence of other risk factors for bleeding or thromboembolism 1.
- The management of anticoagulation in patients undergoing CABG should be individualized and based on a careful assessment of the patient's risk factors and clinical status 1.
Overall, the management of anticoagulation in patients undergoing CABG requires careful consideration of the risks and benefits of anticoagulant therapy, as well as close monitoring and adjustment of the anticoagulation regimen as needed to minimize the risk of bleeding complications and optimize patient outcomes.
From the Research
Target INR for CABG Patients on Warfarin
- The target International Normalized Ratio (INR) for patients undergoing Coronary Artery Bypass Grafting (CABG) while on warfarin is not universally established, but studies provide some guidance:
- A study published in 2018 2 used an INR range of 2-3 for patients on warfarin after CABG.
- Another study from 2025 3 used an INR target of 1.8-2.5 for patients on warfarin and aspirin after CABG, and found that this regimen significantly reduced graft failure rates and improved cardiac function.
- An earlier study from 2001 4 evaluated the effects of warfarin titration in post-CABG patients and found that INR values increased with warfarin dose increments, but did not establish a specific target INR range.
- It is essential to note that the optimal INR target may vary depending on individual patient factors and the specific clinical context.
Clinical Outcomes and INR Targets
- The choice of anticoagulation regimen and INR target should be based on careful consideration of the patient's risk factors, surgical procedure, and potential benefits and risks of anticoagulation:
- A review from 2021 5 highlighted the variability in evidence regarding anticoagulation and antiplatelet therapy after CABG, and emphasized the need for further research to determine the optimal regimens for different patient groups.
- Another study from 2006 6 compared the use of unfractionated heparin and low-molecular-weight heparin as bridging therapy in patients on long-term oral anticoagulants, but did not specifically address INR targets for CABG patients on warfarin.