First in Human Use of Non-invasive, Robot Assisted, High Intensity Focused Ultrasound Treatment of Femoral Atherosclerosis: A Safety and Feasibility Pilot Study

Objective: Currently available open or endovascular revascularisation options for peripheral arterial disease (PAD) have limited long term patency rates and pose a risk of peri-operative complications. Robot assisted, high intensity focused ultrasound (HIFU) enables precise targeting of atherosclerotic plaques, creating thermal lesions with submillimetre resolution. As a non-invasive alternative, HIFU may be associated with fewer peri-operative risks. Pre-clinical studies in healthy and atherosclerotic animals have demonstrated the safety of HIFU treatment. This first in human study investigated the safety and feasibility of HIFU therapy for PAD. Methods: This first in human, single centre, non-randomised pilot study included patients with symptomatic PAD (Rutherford 2 – 4) with a common femoral and or proximal superficial femoral artery stenosis. Lesions with a calcified volume > 80% or localised at a depth of > 35 mm from the skin were excluded. Included patients were treated under sedation with a dual mode ultrasound array (DMUA) system connected to a robotic arm to precisely deliver image guided HIFU to the atherosclerotic plaque. Primary outcomes were: the major complication rate defined as the composite of any complication requiring re-intervention, amputation, or death, which were adjudicated by two independent medical monitors; and technical feasibility defined as successful targeting of the complete lesion. Secondary outcomes included any other procedure related complications, clinical endpoints such as ankle brachial index, and imaging parameters. Results: Between June 2019 and April 2024, 232 limbs in 205 patients were screened. Twelve patients with unilateral lesions underwent HIFU treatment by the same team. The mean treatment time was 113 ± 28.2 minutes, and technical success was achieved in all patients. No major complications or other procedure related complications occurred within 30 days of the procedure or during three months of follow up. No clear differences were observed throughout follow up relative to baseline for the secondary outcomes. Conclusion: HIFU treatment using a DMUA transducer appears safe and feasible for the treatment of selected patients with PAD localised in the femoral artery.