Evolution of deep venous thrombosis: A 2-year follow-up using duplex ultrasound scan and strain-gauge plethysmography

Objective: The development of the post-thrombotic syndrome (PTS) and recurr ence of deep venous thrombosis (DVT) are not yet fully understood. The aim of the study was to identify factors that lead to the long-term complicatio ns of DVT. Methods. In a 2-year prospective follow-up study, duplex scanning and strai n-gauge plethysmography were used to evaluate DVT in relation to the develo pment of long-term complications. Each of the 12 segments examined was assi gned as a thrombosis score (TS). A total TS was calculated for each leg. Pa tent segments were assigned a TS = 0, noncompressible vein segments with fl ow TS = I and noncompressible vein segments without flow TS = 2. The degree of resolution of DVT and the incidence, timing, and outcome of further thr ombotic events were measured during 24 months of follow-up. Results. The study involved 86 legs with DVT. The 2-year follow-up was comp leted for 70 legs. Within 3 months, only 1% of the originally occluded prox imal deep vein segments were still occluded. Between all time intervals, fr om month 12 to month 24, for example, thrombus regression continued in 36% of the legs and thrombus propagation continued in 27%. Multiple regression analysis revealed that an increase in age (P =.008) and proximal location o f the original DVT (P =.05) was significantly related to thrombus propagati on. Multiple regression analysis showed that the risk factors for clinical signs of PTS were a high venous outflow resistance after 1-month and 12-mon th follow-ups (P less than or equal to .002) and a high thrombosis score in the proximal veins after 3 months (P =.008). Conclusions. In the follow-up of older patients and patients with proximal DVT, evolution was shown to be an unstable process with continuing propagat ion for 2 years. The risk factors for the development of PTS were a slow de crease in venous outflow resistance or a high thrombosis score of the proxi mal veins after 3 months.