Changing Features of Proximal Vein Thrombosis Over Time

Recently, the sensitivity of impedance plethysmography (IPG) for the diagnosis of acute deep-vein thrombosis (DVT) in symptomatic outpatients has been questioned. In order to verify whether a change in the venographic pattern of DVT has occurred over years, accounting for the decreased sensitivity of IPG, the authors compared two series of consecutive venograms demonstrating proximal DVT, performed between 1984-1988 (166 patients) and 1990-1992 (140 patients). They evaluated both the extension and the occlusiveness of deep-vein thrombi in the two series. Moreover, changes in the referral characteristics of patients were investigated. In the second series of venograms a significant decrease in thrombi extension, expressed by a lower prevalence of iliac vein thrombosis (29% versus 43%; P = 0.0074) was observed; moreover, a significant increase in the prevalence of nonocclusive thrombi (22% versus 8%; P = 0.0004) was also recorded in the second series when compared with the first. During the study period, among the referral characteristics of patients, the authors observed both a significant decrease in the prevalence of proximal DVT (from 31% to 24%; P < 0.01) and a slight and not statistically significant decrease in the median time elapsed between onset of symptoms and referral for objective testing (from eight and a half to seven days). In conclusion, proximal deep-vein thrombi are currently less extensive and occlusive than observed in the past. These results might depend on earlier referral of less symptomatic patients and might explain the recently reported decrease in IPG sensitivity for proximal DVT.