Patient-Specific AAA Wall Stress Analysis: 99-Percentile Versus Peak Stress

AbstractObjectiveBiomechanically, rupture of an Abdominal Aortic Aneurysm (AAA) occurs when the stress acting on the wall due to the blood pressure, exceeds the strength of the wall. Peak wall stress estimations, based on CT reconstruction, may be prone to observer variation. This study focuses on the robustness and reproducibility of AAA wall stress assessment and the relation with geometrical features of the AAA.MethodsThe AAAs of twenty patients were reconstructed by three operators. Both the peak and 99-percentile stress were used for intra- and inter-operator variability using the intraclass correlation coefficient (ICC). A regression analysis was performed to relate the stress parameters with the maximum diameter. Outliers were analyzed by their geometrical characteristics.ResultsThe intra-operator ICC was 0.73–0.79 for the peak stress and 0.94 for the 99-percentile stress. The inter-operator ICC was 0.71 for the peak stress and 0.95 for the 99-percentile stress. A significant linear relation with the diameter was found only for the 99-percentile stress.ConclusionsThe 99-percentile stress is more reproducible than peak wall stress. A significant relation between wall stress and diameter was found. Other geometrical features had no statistical relation with high stress

Abdominal Aortic Aneurysms with High Thrombus Signal Intensity on Magnetic Resonance Imaging are Associated with High Growth Rate

Cardiovascular Aspects of Radiolog

Plasma levels of matrix metalloproteinase-9: A possible diagnostic marker of successful endovascular aneurysm repair

AbstractObjectiveThe aim of the study was evaluating the diagnostic value of plasma matrix metalloproteinase- (MMP)-2 and -9 and tissue inhibitor of MMP-1 (TIMP-1) for endoleak detection after endovascular aneurysm repair (EVAR).ReportConsecutive EVAR patients (n = 17) with endoleak and matched controls without endoleak (n = 20) were prospectively enrolled. Increased levels of MMP-9 were observed in patients with endoleak (P < 0.001). Regression analysis showed no significant influence of age, sex or abdominal aortic aneurysm (AAA) size. The receiver operating characteristic (ROC) curve of plasma MMP-9 levels showed that a cut-off value of 55.18 ng ml−1 resulted in 100% sensitivity and 96% specificity with an AUC value of 0.988 (P < 0.001) to detect endoleak.ConclusionsPlasma MMP-9 levels appear to discriminate between patients with and without an endoleak with high sensitivity and specificity

The influence of wall stress on AAA growth and biomarkers

Objectives: This study investigated the relation between abdominal aortic aneurysm (AAA) wall stress, AAA growth rate and biomarker concentrations. With increasing wall stress, more damage may be caused to the AAA wall, possibly leading to progression of the aneurysm and reflection in up- or downregulation of specific circulating biomarkers. Levels of matrix metalloproteinase-9, tissue inhibitor of matrix metalloproteinase-1, C-reactive protein and alpha 1-antitrypsin were therefore evaluated.MethodsThirty-seven patients (maximum AAA diameter 41–55 mm) with two, three or four consecutive computed tomography angiography (CTA) scans were prospectively included. Diameter growth rate in mm/year was determined between each pair of two sequential CTA scans. AAA wall stress was computed by finite element analysis, based on the first of the two sequential CTA scans only (n = 69 pairs). Biomarker information was determined in 46 measurements in 18 patients. The relation between AAA diameter and wall stress was determined and the AAA's were divided into three equally sized groups (relative low, medium and high stress). Growth rate and biomarker concentrations were compared between these groups. Additionally, correlation coefficients were computed between absolute wall stress, AAA growth and biomarker concentrations.ResultsA relative low AAA wall stress was associated with a lower aneurysm growth rate. Growth rate was also positively related to MMP-9 plasma concentration (r = 0.32). The average MMP-9 and CRP concentrations increased with increasing degrees of relative wall stress, although the absolute and relative wall stress did not correlate with any of the biomarkers.ConclusionAlthough lower relative wall stress was associated to a lower AAA growth rate, no relation was found between biomarker concentrations and wall stress. Future research may focus on more and extensive biomarker measurements in relation to AAA wall stress