<b><i>Objectives:</i></b> To assess the delayed (15 days) histological and ultrastructural changes occurring following endovascular treatment with a direct aspiration first pass technique (ADAPT) or stent retrievers (SRs) and to compare the findings in order to determine which is the least harmful technique and what changes occur. <b><i>Materials and Methods:</i></b> Damage to the wall of swine extracranial arteries was evaluated after ADAPT with the Penumbra system or thrombectomy with various SRs. The procedures were performed using two pigs as animal models; extracranial cervical arteries were selected based on their diameters in order to reproduce the procedures as in human intracranial arteries, and endovascular thrombectomies were done after the injection of autologous thrombi. Two weeks later, the animals were euthanized, and 60 arterial samples were obtained for analysis by optical and electron microscopy. <b><i>Results:</i></b> Optical and electron microscopy revealed that both techniques cause, in different way, alterations to the structure of the vessel wall. <b><i>Conclusions:</i></b> Both techniques caused damage to the vessel wall. The main damages were localized at the level of the tunica media and adventitia, instead of the tunica intima as in the acute phase. Further investigation is required to better understand whether these alterations could have chronic consequences.