How to manage anticoagulation in a patient with a mechanical Aortic Valve Replacement (AVR) and Impaired renal function, who requires a below-the-knee amputation (BKA) with an International Normalized Ratio (INR) of 2.2, after discontinuing Warfarin (coumarin)?

From the Guidelines

For this 65-year-old male with a mechanical aortic valve who needs a below-the-knee amputation, the best approach is to start IV unfractionated heparin when INR <2, and operate when INR <1.3. This bridging anticoagulation strategy is necessary because the patient has a mechanical heart valve, which carries a high risk of thromboembolism when anticoagulation is interrupted, as recommended by the 2020 ACC/AHA guideline for the management of patients with valvular heart disease 1. Unfractionated heparin is preferred over LMWH in this case because the patient has moderate renal impairment (creatinine 1.3 mg/dL) and because IV heparin offers more precise control of anticoagulation. The heparin can be discontinued 4-6 hours before surgery and restarted after hemostasis is achieved, typically 12-24 hours post-operation, as suggested by the 2017 AHA/ACC focused update of the 2014 AHA/ACC guideline for the management of patients with valvular heart disease 1. This approach provides continuous anticoagulation protection while allowing for a safe surgical window with normalized coagulation parameters. Simply waiting for the INR to drop without bridging therapy or using aspirin alone would leave the patient with a mechanical valve at unacceptable risk for valve thrombosis and systemic embolism during the perioperative period. Key considerations in this decision include the patient's mechanical valve, lack of prior thromboembolic events, and normal left ventricular function, as well as the need for a safe and effective perioperative anticoagulation strategy. The patient's current INR of 2.2 and creatinine of 1.3 mg/dL also support the use of IV unfractionated heparin as a bridging agent. Overall, this approach prioritizes the patient's safety and minimizes the risk of thromboembolic and bleeding complications.

From the FDA Drug Label

Periodically monitor platelet counts, hematocrit, and occult blood in stool during the entire course of heparin therapy, regardless of the route of administration. The dosing recommendations in Table 1 are based on clinical experience be adjusted for the individual patient according to the results of suitable laboratory tests, the following dosage schedules may be used as guidelines: 2.5 Cardiovascular Surgery Patients undergoing total body perfusion for open-heart surgery should receive an initial dose of not less than 150 units of heparin sodium per kilogram of body weight.

The patient requires anticoagulation management prior to below-the-knee amputation (BKA) with a target INR < 1.3.

• Since the patient's current INR is 2.2, warfarin has been discontinued.
• To manage anticoagulation, start IV unfractionated heparin when INR < 2, and operate when INR < 1.3 2.
• This approach ensures continuous anticoagulation while minimizing the risk of bleeding complications during surgery.
• Monitoring of platelet counts, hematocrit, and occult blood in stool is crucial during heparin therapy 2.

From the Research

Management of Anticoagulation

The patient has a mechanical aortic valve and requires below-the-knee amputation, with an INR of 2.2 that needs to be reduced to <1.3.

• Discontinuing warfarin is the first step, as the patient's current INR is 2.2 and needs to be lowered.
• According to the study 3, rapid anticoagulation can be achieved either with unfractionated heparin or with low-molecular weight heparin (LMWH) when warfarin therapy is temporarily discontinued.
• However, the study 4 suggests that long-term use of LMWH can lead to mechanical aortic valve dysfunction, and the study 5 found that bridging anticoagulation therapy with heparin increases the chances of bleeding in the postoperative phase for mechanical aortic valve replacement patients.
• The study 6 found that higher-intensity anticoagulation was significantly associated with any bleeding, and there were few thromboembolic events across both groups.
• The study 7 demonstrated that a low target-INR anticoagulation regimen is safe in selected aortic valve patients with the Medtronic Open Pivot mechanical prosthesis, without increasing the thromboembolic complication rate while lowering the hemorrhagic events.

Recommended Approach

Based on the studies, the recommended approach would be to:

• Start IV unfractionated heparin when INR <2, and operate when INR <1.3, as this approach allows for rapid anticoagulation and minimizes the risk of bleeding and thromboembolic events 3, 5.