Antithrombotic Therapy in Peripheral Arterial Occlusive Disease: Low-intensity oral anticoagulant therapy
Very low-intensity oral anticoagulant therapy (international normalized ratio [INR] 1.5 to 2) combined with low-dose aspirin therapy (80 to 325 mg) is an attractive antithrombotic regimen that theoretically would retard thrombin generation in addition to inhibiting platelets. Lower doses of these combined agents might offer superior antithrombotic effectiveness while minimizing hemorrhagic side effects. This combination was evaluated in a recently presented, but as-yet unpublished, multicenter study conducted in Veterans Affairs hospitals (level I). Four hundred fifty-eight patients were randomized to either aspirin alone (325 mg/d) or aspirin and warfarin (INR 1.5 to 2.8). Treatment was initiated after surgery. Femoropopliteal bypass was performed in 37% of cases and femorotibial or femoropedal bypass in the others. The 4-year primary patency rates were not different (aspirin, 77%, vs aspirin plus warfarin, 74%). Of note, approximately 75% of patients in the aspirin with warfarin group either had subtherapeutic warfarin levels or had discontinued warfarin during the study.
The effect of the combination of warfarin and aspirin on the patency of infrainguinal vein bypass grafts at high risk for thrombosis was evaluated in a single-center, randomized clinical trial of 56 patients (level II). Aspirin dosage was 325 mg/d, and warfarin was given to maintain the INR between 2 and 3. Patients randomized to warfarin received heparin anticoagulation postoperatively, which was converted to warfarin. Unlike the previously mentioned trials, only grafts at high risk for failure were included. These risk factors were marginal quality vein, poor arterial runoff, and previously failed bypass. Bypass to the tibial arteries was performed in 90% of patients further birth control online. The 3-year primary patency rate (78 vs 41%) and the limb salvage rate were significantly higher in those randomized to warfarin. Although there were more hematomas in the warfarin group (35 vs 3.7%), the overall complication rate was no different between groups. Although a benefit from the routine use of oral anticoagulation after uncomplicated femorotibial bypass procedures has not been demonstrated, patients considered to be at high risk for thrombosis might be a subgroup in which such a benefit exists, and they should be considered for postoperative anticoagulation.