Transmural pressure for conceptualisation of chronic venous insufficiency management

We read with interest the article of Normahani et al. published in Phlebology. ¹ The authors repurpose the Guytonian equation to facilitate our understanding of the clinical manifestations and treatment possibilities of chronic venous insufficiency (CVI). Based on the hemodynamic response to a non-thrombotic lesion of the iliac vein, they propose three treatment options: i. Stenting the iliac vein; ii. Limb compression; iii) Superficial venous ablation. Considering the excess transmural venous pressure (TMP) (differential pressure inside and outside the venous wall) upstream of the iliac vein lesion, as the cause not only of the dilation of the venous ducts, but also of its overall effect on the micro-circulation which hampers the drainage of tissues, the options i–ii are both favourable to the decrease of TMP. Indeed, stenting reduces internal venous pressure and compression increases external venous pressure, both concurring in improving TMP and consequently the CVI clinical course. ² Conversely, superficial venous ablation does not correct the excess TMP. Indeed, it would not significantly increase the internal pressure to cross or bypass the iliac vein lesion; moreover, the haemodynamic advantage of the elimination of reflux is overtime mitigated by the progressive worsening of venous compliance (pressure/volume relationship curve), quite recently assessed following great saphenous vein ablation. ³ The steeper compliance curve following saphenous ablation means the need of an increase in pressure to accommodate blood into the venous system of the lower limb. ⁴ Such an effect of saphenous ablation generates an excess TMP transmitted into the superficial microcirculation. According to Starling law, increased TMP may favour cutaneous trophic consequences (oedema, hypodermitis, ulcer) and varicose recurrences, as well. ² In addition, the ablated superficial veins could be dramatically missing as a potential compensatory pathway in the event of subsequent stent occlusion.