Deep vein thrombosis outcome and the level of oral anticoagulation therapy

Objective: The purpose of this study was to assess the rate of deep vein th rombosis (DVT) resolution and DVT outcomes as functions of the level of ora l anticoagulation therapy achieved with warfarin. Methods: In 33 consecutive patients, a series of 35 limbs with acute sympto matic DVT was followed throughout 1 year of anticoagulation therapy. All th e patients underwent 5 days of intravenous unfractionated sodium heparin th erapy that was adjusted in dose to prolong the activated thromboplastin tim e to 2.0 to 2.5 times the control. In addition, warfarin was administered f or a period of 6 months, with a target international normalized ratio (INR) between 2.0 and 3.0. All the patients underwent venous duplex scanning and physical examination at the time of diagnosis and at 1 week, 1 month, 3 mo nths, 6 months, and 1 year. Results: At the end of the 1-year study period, the rate of complete DVT re solution was 68%. The median INR values in patients with complete DVT resol ution were significantly higher than those of patients with incomplete DVT resolution after 1, 3, and 6 months of treatment with warfarin. In addition , the proportion of patients with INR values below therapeutic range was si gnificantly higher in patients with incomplete DVT resolution than in patie nts with complete DVT resolution after 1, 3, and 6 months Of treatment with warfarin. The presence of occlusive thrombi was associated with incomplete DVT resolution. Of the patients with occlusive thrombi, 62% had chronic ve nous insufficiency symptoms develop, whereas only 11% of the patients with nonocclusive thrombi (P =.003) had these symptoms develop. Conclusion: Despite 6 months of oral anticoagulant therapy, almost one thir d of thrombi did not resolve completely. The INR values were significantly higher in those patients with complete DVT resolution. These results sugges t that the maintenance of an INR level between 2.0 and 3.0 throughout oral anticoagulation therapy will minimize the rate of incomplete DVT resolution .