Natural history of proximal deep vein thrombosis assessed by duplex ultrasound

The late sequelae of an acute deep vein thrombosis (DVT) are difficult to predict. There are many retrospective studies which suggest that the post-phlebitic syndrome is associated with the development of valvular incompetence but these have lead to little understanding of the changes involved in the venous system following an acute thrombotic event. Duplex ultrasound imaging is an useful method to study changes in the venous system because it can locate a thrombus, assess the changes which occur over time and monitor the development of recanalization and reflux of blood flow.

In this study, 50 patients were followed by serial duplex ultrasound examination to determine if a more accurate prediction of patients at risk could be found. Rapid thrombolysis and extent of the thrombosis are both factors which influence the return of the vein to normal function.

Complete thrombolysis within a short period of time occurred in 24% of patients resulting in preserved valvular function. After one year there were 34% with early post-phlebitic symptoms. All of these patients had veins which recanalized slowly and developed valvular incompetence with reflux. Veins remained occluded in 14% of patients and of these 8% had competent collateral channels. This appeared to be a better outcome because none of these patients had developed symptoms after one year. Recurrent DVT's occurred in 8% within the year. Of these, 4% presented with symptoms and 4% were without symptoms but thrombus was found by ultrasound examination.

Serial duplex examination leads to better understanding of the natural history of an acute DVT. This may have clinical implications and lead to better management of acute DVT thereby reducing the long term risks of the post phlebitic limb.