A volumetric index for the quantification of deep venous thrombosis

Purpose The evaluation of treatment strategies for deep venous thrombosis ( DVT) is assessed through the nse of a reliable method of quantifying the ex tent of the thrombotic process. Previous indices of thrombus burden have su ffered from various limitations, including lack. of clinical relevance, poo r correlation with actual thrombus mass, and failure to include important v enous segments in the methodology The use of a novel scheme of quantifying venous thrombus was evaluated as an alternative method that would avoid som e of the drawbacks of existing indices. Methods: The volumes of 14 venous segments (infrarenal inferior vena cava, common iliac, hypogastric, external iliac, common femoral, profunda, superf icial femoral, and popliteal and six tibial veins) were calculated from com puted tomography (pelvic vein diameter), duplex ultrasound scan (infraingui nal vein diameter), and contrast venography (length of all segments) measur ements. A venous volumetric index (VVI) was assigned with the normalization of the values to the volume of a single calf vein. The VVI was validated w ith the assessment of the ability to discriminate between asymptomatic and symptomatic DVT and between those DVT that were associated with pulmonary e mboli and those that were not. Results: With the imaging data, the VVI ranged from 1 for a single calf vei n thrombus to 26 for the infrarenal inferior vena cava. Each VVI unit repre sented 2.3 mt of thrombus, with a maximum possible score of 63 representing a thrombus burden of 145 mL,for a single extremity, including the infraren al inferior vena cava, In 885 patients with DVT, the WT ranged front 1 to 5 6, aver averaging 3.9 +/- 0.2 in patients who were asymptomatic and 8.7 +/- 0.3 in patients who were symptomatic (P < .001). The VVI was similar in th e patients with pulmonary emboli as compared with those without (9.6 +/- 1. 2 vs 7.7 +/- 0.2, respectively), In comparison with the three existing meth ods of quantifying venous thrombus burden, the receiver operating character istic curve analysis results suggested that the VVI and the Venous Registry index were better than the other two indices in the discrimination of pati ents with symptomatic and asymptomatic DVT (P < .001). Conclusion: A novel index of venous thrombus burden, on the basis of actual venous volume measurements, was more accurate than present indices in the differentiation between clinical categories of patients with DVT, As such, it offers an acceptable alternative to current scoring systems.