Endovenous laser ablation is a common therapy of great saphenous vein insufficiency with a very high success rate. It works by heating and thereby obliterating the vein. Steam ablation is a new therapy that also works by heating and thereby obliterating the vein. The hypothesis of this study is that steam ablation is as effective as laser ablation, but that it results in better secondary outcomes (e.g., lower pain scores).

The study is a randomized clinical trial comparing two different therapies for endovenous ablation of great saphenous veins. The aim of the study is to test whether the anatomical success rate of Steam Ablation is not inferior to that of Endovenous laser ablation (EVLA) in treatment of great saphenous vein insufficiency and compare the treatment safety, patient reported outcomes and cost-effectiveness analyses between EVLA and Steam Ablation.

Inclusion Criteria:

• Patients over 18 years old
• Insufficiency of the GSV measured with ultrasound imaging, reflux > 0.5 s, and diameter of vein > 0.5 cm
• Symptoms of chronic venous insufficiency
• No prior treatment of the insufficient GSV
• Informed consent

Exclusion Criteria:

• Acute deep or superficial vein thrombosis
• Agenesis of deep vein system
• Vascular malformation or syndrome
• Post-thrombotic syndrome, occlusive type
• Pregnancy
• Immobility
• Allergy to lidocaine
• Arterial insufficiency