The observation of below-the-knee artery by optical frequency domain image and angioscopy: a case series.

Background: Endovascular treatment (EVT) is a well-established treatment for patients with chronic limb-threatening ischaemia, and below-the-knee (BTK) artery is its main target, although the re-intervention rate is still high. Understanding of the characteristics of BTK artery atherosclerosis would be required to overcome this issue. In this case series, we elucidated the characteristics of non-stenotic BTK artery atherosclerosis in the patients who received EVT of the superficial femoral artery (SFA) using optical frequency domain imaging (OFDI) and angioscopy. Case summary: We presented five patients who underwent EVT of SFA and subsequent observation of ipsilateral BTK artery using OFDI and angioscopy. Patients one and two had advanced atherosclerosis; however, patients three, four, and five had only mild atherosclerosis. Discussion: All patients had multiple risk factors for atherosclerosis and stenosis/occlusion of the SFA and ipsilateral BTK arteries. Furthermore, some patients had several other atherosclerotic vascular diseases suggesting the presence of advanced systemic atherosclerosis. On the other hand, some patients with multiple BTK artery stenosis/occlusion did not have advanced atherosclerosis in the examined BTK artery. The absence of significant atherosclerosis in a BTK artery in patients with multiple stenoses or occlusion in other ipsilateral BTK arteries may suggest some mechanism of vessel occlusion other than atherosclerosis. Further investigations are needed to clarify the mechanism.