Which condition would contraindicate endovenous thermal ablation (EVTA) of the right great saphenous vein (GSV)?

The presence of a previous deep vein thrombosis (DVT) with moderate obstruction of the right femoral vein contraindicates endovenous thermal ablation (EVTA) of the right great saphenous vein (GSV) because the procedure could pose significant risks in patients with compromised venous outflow. EVTA relies on thermal energy to effectively close off the affected vein, which could lead to further complications if there's already an obstruction present.

The risk of thromboembolic events may increase if EVTA is performed in the context of a significant history of DVT and obstruction. This disruption of normal venous anatomy would heighten the chance of worsening venous insufficiency or causing higher pressures within the venous system, potentially resulting in adverse outcomes.

Conditions like a previous history of superficial thrombophlebitis, the presence of spider veins, and major limb swelling may warrant a cautious approach or additional evaluation, but they do not inherently prevent the procedure as significantly as a history of DVT with existing venous obstruction does. Therefore, prior DVT with obstruction presents a more critical contraindication for conducting EVTA in this scenario.