Quantifying saphenous reflux

Abstract

Background: Quantification of reflux is desirable in advanced chronic venous disease as clinical features are based on its adverse impact on ambulatory venous pressure (AMVP). Prior clinical observation suggests that reflux in a saphenous vein > 5 mm is likely significant. On the basis of normal calf pump mechanics, we hypothesized that a reflux volume ≥ 30 mL was necessary to upset pump equilibrium.

Methods: Venous laboratory data in 119 limbs with isolated saphenous reflux were analyzed. Reflux volume was calculated by duplex ultrasound (area × velocity × duration). The relationship of reflux volume to saphenous size, calf pump function (air plethysmography, AMVP), flow resistance (Poiseuille equation), and clinical severity were examined.

Results: Saphenous size had a bimodal relationship to reflux volume. Reflux volume of ≥ 30 mL occurred mostly (97% of limbs) with saphenous size of ≥ 5.5 mm, but 51% of saphenous veins >5.5 mm had reflux volumes <30 mL. This is because saphenous veins invariably carried less than their maximum reflux potential indicated by their size (Poiseuille equation). Variable additional focal resistance across refluxive valve cusps and narrower re-entry perforators is not taken into account when only saphenous truncal size is used for resistance calculation. Furthermore, the association of AMVP with reflux was found not to be based on a set (≥ 30 mL) threshold but was variable, depending on existing calf pump mechanics, compensatory in some (12% of limbs) and aggravating reflux effects in others (26%). Calf pump abnormalities were found in 70% of refluxive limbs and in 44% (n = 16) of contralateral limbs without any reflux. Reflux volume was significantly higher overall in limbs with ulcer (C6), but the range overlapped with lesser clinical classes. Seven of 14 limbs with active ulcers had reflux volume >30 mL; six of seven limbs with active ulcers and reflux volume of <30 mL had calf pump abnormalities that would be poorly tolerant of reflux even at these smaller volumes.

Conclusions: Saphenous size alone cannot be used as an indicator of significant reflux. More than two thirds of the limbs with isolated saphenous reflux have calf pump abnormalities, which also occurred without reflux in the opposite limb--a novel finding. This means that in addition to quantification of reflux volume, calf pump assessment such as with air plethysmography and AMVP is desirable in clinical classes 3 and higher for proper assessment.