Intraluminal thrombus volume correlates with the crural vessel runoff in popliteal artery aneurysms upon initial presentation

<b></b> <i>Background:</i> Patients having emergency surgery due to ischemia caused by a popliteal artery aneurysm (PAA) have worse outcomes in all endpoints (operation time, major adverse limb events (MALE), amputation-free survival) than after elective treatment, mostly due to a limited crural vessel runoff. This study investigates the relationship between PAA diameter, volume, and luminal thrombus load in relation to the preoperative crural runoff. <i>Patients and methods:</i> Retrospective single-centre evaluation of surgically treated patients with PAA and semi-automated quantitative CT analysis of PAA morphologies (diameter, volume and intraluminal thrombus volume). Primary endpoints were the correlations these characteristics with the number of patent crural vessels. <i>Results:</i> A total of 89 PAAs (61 patients, median age 75, IQR 12; 94.4% male) were identified, of which 47.2% were symptomatic with 18 acute limb ischemia (ALI). The diameter at surgery was 33.8 ± 12.1mm and the volume 68.5 ± 13.6mm³. A median of two lower leg vessels were patent (elective 3 [1, 2, 3] vs. emergency 1 [1, 2], p=0.1) upon preoperative CTA. 77 PAAs underwent elective surgery, five PAAs (5.6%) received endovascular treatment. The surgical complication rate was 23.6% without immediate or early occlusion. The follow-up was 42.5 [39-45] months. The overall mortality rate was 11.2% and the primary patency rate 73.9%. While the total aneurysm volume correlated well with the diameter (r=0.77, p<0.01), the intraluminal thrombus volume (ILT) showed the clearest correlation with the crural runoff (r=-0.34, p=0.01). No correlation between the diameter and crural runoff was observed (r=-0.17, p=0.1). A reduced crural run-off was significantly associated with impaired amputation-free survival (p=0.01). A subgroup analysis (n=21) with sequential CTs showed a tendency towards greater increase of thrombus volume compared to plain diameter during PAA growth. The thrombus volume index (=ILT/total PAA volume) was significantly higher in emergency patients (p=0.01), while diameters tended to be smaller (p=0.57). <i>Conclusions:</i> The increasing intraluminal thrombus volume correlates most distinctly with a reduced crural runoff in PAAs and should therefore be considered prognostically important, especially in the presence of an increased growth rate compared to the diameter.