Venous thrombus stability during acute phase of therapy

The purpose of this study was to use serial venous duplex scans to document the status of deep venous thrombi during the early phase of therapy for ac ute, deep-vein thrombosis (DVT). A total of 71 consecutive participants tre ated for a first episode of acute DVT were monitored for new venous thrombo sis using serial venous duplex scans. An average of 4.6 duplex scans were p erformed per patient (range, three to seven) during the 3-week study period . The cumulative incidence of contiguous/non-contiguous extension of the DV T at 3 weeks was 26% (95% CI = 14% to 38%), Nine of the 15 (60%) occurrence s were asymptomatic. None of the classical risk factors for DVT was signifi cantly associated with the development of new thrombi, The fraction of time during which the level of anticoagulation was considered 'adequate' (inter national normalized ratio greater than or equal to 2.0 and/or heparin conce ntration greater than or equal to 0.2 IU/ml) was inversely associated with the risk of extension/new thrombi (p = 0.01, Cox proportional hazards analy sis), It was concluded that: (1) the frequency of contiguous/non-contiguous exten sion of venous thrombosis detectable during the first 3 weeks of therapy wa s higher than previously reported; (2) the majority of the occurrences were asymptomatic; and (3) the risk of developing this complication was inverse ly associated with the level of anticoagulation achieved.