Calf volume changes with venous occlusion air plethysmography in assessment of patients after deep venous thrombosis.

BACKGROUND: This is an analysis of the hemodynamic response of post-thrombotic legs to a sustained thigh compression and quick-release maneuver. This is an integral part of the investigation of venous occlusion plethysmography that has been promoted as a way of assessing the venous return. The aim was to quantify the venous volume changes in patients after deep venous thrombosis (DVT) and to determine whether refluxing legs differed from obstructed legs.

METHODS: The inflow and outflow air plethysmography tracings of 332 of 519 legs were examined retrospectively. These tracings from 192 patients were performed between 1989 and 1999. The median age was 51 (17-89) years; 65% of the patients were men, and 52% were left legs. The retrospective clinical class distribution (%) by the Clinical, Etiologic, Anatomic, and Pathologic (CEAP) classification was as follows: C0 = 5.4, C2 = 3.3, C3 = 68.4, C4 = 13, C5 = 3.6, C6 = 6.3. Inclusion criteria were a history of DVT and a duplex ultrasound examination documenting the site and type of deep venous disease. Ascending phlebography was performed in 28% of patients to complement duplex ultrasound in assessing the site of disease. Reflux was defined as reverse flow (>1 second) and obstruction as luminal narrowing, wall irregularity, or luminal echogenic material. Air plethysmography was performed in the supine position. After calibration with 100 mL of air, a thigh cuff was inflated to 80 mm Hg, and the resulting increase in calf volume was recorded by the sensor calf cuff with an ink trace on graphic paper. At the volume plateau, the thigh cuff was deflated suddenly to record the decrease in calf volume.

RESULTS: Reflux alone was identified in 19.6% of limbs and obstruction alone in 42.2%. Iliofemoral involvement was identified in 56.6%. The thigh compression/release maneuver caused a significant median (interquartile range) net reduction in calf volume by 9 (5-15) mL (P < .0005, Wilcoxon). The outflow volume was significantly greater than the inflow volume overall and also when legs were separated into categories on the basis of their site and type of disease (P < .0005, Wilcoxon). There was no significant difference in calf volume change in legs with iliofemoral involvement compared with those with distal disease. However, pure refluxing legs had significantly greater inflow and outflow volumes compared with legs with pure obstruction (P < .0005), with a median (interquartile range) reduction in calf volume of 13 (8-18) mL (reflux group) vs 7 (2-13) mL (obstruction group) (P < .0005, Mann-Whitney).

CONCLUSIONS: Thigh compression significantly improves the venous return in patients after DVT evidenced by a greater absolute reduction of calf volume. This change was significantly greater in pure refluxing legs than in those with obstruction alone.