Strain patterns with ultrasound for improved assessment of abdominal aortic aneurysm vessel wall biomechanics

ABSTRACT Background Abdominal aortic aneurysms (AAAs) are an important cause of death. Small AAAs are surveyed with ultrasound (US) until a defined diameter threshold, often triggering a CT scan and surgical repair. Nevertheless, 5-10 % of AAA ruptures are below threshold, and some large AAAs never rupture. AAA wall biomechanics may reveal vessel wall degradation with potential for patient-centred risk assessment. This clinical study investigated AAA vessel wall biomechanics and deformation patterns, including reproducibility. Methods In 50 patients with AAA, 183 video clips were recorded by two sonographers. Prototype software extracted AAA vessel wall principal strain characteristics and patterns. Functional principal component analysis (FPCA) derived strain pattern statistics. Results Strain patterns demonstrated reduced AAA wall strains close to the spine. The strain pattern ‘topography’ (i.e., curve phases or ‘peaks’ and ‘valleys’) had a 3.9 times lower variance than simple numeric assessment of strain amplitudes, which allowed for clustering in two groups with FPCA. A high mean reproducibility of these clusters of 87.6 % was found. Median pulse pressure-corrected mean principal strain (PPPS) was 0.038 %/mmHg (interquartile range: 0.029 to 0.051 %/mmHg) with no correlation to AAA size (Spearman’s ρ = 0.02, FDR-P = 0.15). Inter-operator reproducibility of PPPS was poor (limits of agreement: ±0.031 %/mmHg). Discussion Strain patterns challenge previous numeric stiffness measures based on AP-diameter and are reproducible for clustering. This study’s PPPS aligned with prior findings, although clinical reproducibility was poor. In contrast, US-based strain patterns hold promising potential to enhance AAA risk assessment beyond traditional diameter-based metrics.