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
.