Intravascular ultrasound imaging for diagnosis and characterization of the popliteal compression syndrome.

Objective: Functional popliteal artery entrapment syndrome (fPAES) is a rare form of nonatherosclerotic claudication most often seen in young athletic patients. Diagnosis remains challenging, with various imaging modalities showing equivocal or subtle findings that may be missed. We sought to critically examine and quantitate the utility of intravascular ultrasound (IVUS) imaging, a common diagnostic tool for vascular compression syndromes, in diagnosis and characterization of fPAES.

Methods: Patients presenting to a single tertiary care center between 2019 and 2022 with symptoms of PAES but without an anatomic etiology or equivocal workup were selected. Angiogram and IVUS with maneuvers were performed on affected extremities at rest, active plantarflexion/dorsiflexion, and plantarflexion/dorsiflexion against resistance. IVUS examination was recorded using a pull-back technique from the tibial vessels to the superficial femoral artery. The degree, length, and anatomic location of compression using the two imaging modalities were compared.

Results: Angiogram and IVUS with maneuvers were performed on 17 lower extremities (9 left, 8 right) in 15 patients (88% female; mean age, 21.2 years). Evidence of arterial compression on angiography was noted in 88.2% (n = 15) of limbs (66.7% complete contrast cessation and 20% popliteal artery tapering); 13.3% (n = 2) only demonstrated sluggish flow as possible evidence of compression. Arterial compression was seen on IVUS imaging in 15 of 17 limbs, and all completely compressed around the IVUS catheter. The IVUS-measured mean length of compression was 10.5 cm ± 4.2 (median, 11 cm; range, 4-23 cm). Compression involved only the popliteal vessels in 86.7% (n = 13); one patient had both popliteal and tibioperoneal trunk compression, whereas another had tibioperoneal trunk and peroneal artery compression. Popliteal vein compression was 100%. The contrast cessation point on angiography and the proximal point of compression on IVUS imaging differed in 80% of cases ( < .05). The distal extent of compression was unable to be determined by angiogram findings but was clearly delineated by IVUS imaging in all cases.

Conclusions: IVUS imaging is a more sensitive diagnostic and descriptive imaging modality compared with angiogram in patients with possible fPAES. IVUS and angiogram findings are greatly discordant; moreover, IVUS imaging can provide detailed information such as the precise extent and anatomic location of the arterial compression, which may be useful in aiding surgical planning. IVUS imaging should be considered the gold standard for diagnosing and characterizing fPAES before intervention planning.