Non thermal HIFU treatment for vein occlusion: Histological evidence from a pre-clinical animal study

ObjectiveThe aim of this preclinical study is to investigate in-vivo veins effects including histological analysis following endovenous cavitation by Non-Thermal High-Intensity Focused Ultrasound (NT-HIFU).MethodsFour lateral saphenous veins (LSV) in two sheep were sonicated using ultrasound guided NT-HIFU device inducing cavitation (Veinsound, Lyon, France) during 30s in 2 LSV (protocol A), 20s in 1 LSV (protocol B), and 10s in 1 LSV (protocol C). Clinical and ultrasound follow-up was performed at 3 and 7 days, venous sampling at 10 days. Four vein sections were available in each LSV. Histological analysis considered percentage of vein lumen obliteration. Vein wall damage was qualified as destruction, fibrosis, and immune infiltration.ResultsObliteration was observed by Duplex Ultrasound in all LSV. Histologic analysis showed total or partial obliteration of the LSV in respectively 15 (93.8%) and 1 case (6.2%). Destruction was observed in the intima in all 16 histology sections, in the media in 11 sections (68.8%) and in the adventitia in five sections (31.2%). Fibrosis was observed in the media in all 16 sections, in the intima in seven sections (43.8%) and in the adventitia in five sections (31.2%). Immune infiltration was observed in the adventitia in eight sections (50%), in the media in five sections (31.2%) and in the intima in one section (6.2%). Resolutive skin damage was observed in one case (protocol A) and mild perivenous tissue remodeling in 3 cases (protocol A and B).ConclusionThis study demonstrated that endovenous cavitation allows to cause vein occlusion in sheep with significant destruction lesions of intima and fibrosis of the media. Appropriate sonication time avoids side effects.