Stress Analysis in AAA does not Predict Rupture Location Correctly in Patients with Intraluminal Thrombus.

BACKGROUND: A biomechanical approach to the rupture risk of an abdominal aortic aneurysm could be a solution to ensure a personalized estimate of this risk. It is still difficult to know in what conditions, the assumptions made by biomechanics, are valid. The objective of this work was to determine the individual biomechanical rupture threshold and to assess the correlation between their rupture sites and the locations of their maximum stress comparing two computed tomography scan (CT) before and at time of rupture. METHODS: We included 5 patients who had undergone two CT; one within the last 6 months period before rupture and a second CT scan just before the surgical procedure for the rupture. All DICOM data, both pre- and rupture, were processed following the same following steps: generation of a 3D geometry of the abdominal aortic aneurysm, meshing and computational stress analysis using the finite element method. We used two different modelling scenarios to study the distribution of the stresses, a "wall" model without intraluminal thrombus (ILT) and a "thrombus" model with ILT. RESULTS: The average time between the pre-rupture and rupture CT scans was 44 days (22-97). The median of the maximum stresses applied to the wall between the pre-rupture and rupture states were 0.817 MPa (0.555-1.295) and 1.160 MPa (0.633-1.625) for the "wall" model; and 0.365 MPa (0.291-0.753) and 0.390 MPa (0.343-0.819) for the "thrombus" model. There was an agreement between the site of rupture and the location of maximum stress for only 1 patient, who was the only patient without ILT. CONCLUSIONS: We observed a large variability of stress values at rupture sites between patients. The rupture threshold strongly varied between individuals depending on the intraluminal thrombus. The site of rupture did not correlate with the maximum stress except for 1 patient.

Scannographic Study of Risk Factors of Abdominal Aortic Aneurysm Rupture.

BACKGROUND: Current decision about when to operate abdominal aortic aneurysms (AAAs) is based only on the maximum aneurysm diameter (MAD). However, small aneurysms still rupture and we can observe very large AAA without any symptom. A simple morphologic analysis could be a tool to assess the risk of rupture. The main objective of this study was to assess the relevance of ratios between MAD and healthy aorta on computed tomography (CT) as a risk factor of AAA rupture. The secondary objective was to evaluate CT signs as risk factors of AAA rupture. METHODS: Retrospective observational bicentric study comparing CT scans of a ruptured AAA group and a control group treated electively was conducted. Appariement 1:1 based on MAD was applied. Ratios between healthy aorta diameters at several levels, celiac trunk (CTR), superior mesenteric artery (SMA), highest renal artery (RA), and the MAD were calculated. The presence of blebs, crescent signs, ruptures of calcifications of the aneurysm sack, and draped aorta were notified. RESULTS: From 2010 to 2016, 38 ruptured AAA and 38 controls were included. Ratios were superior in the rupture group, respectively: MAD/CTR [2.77 (±0.5) versus 2.58 (±0.4) P < 0.095], MAD/SMA [2.92 (±0.7) versus 2.74 (±0.5) P < 0.194], and MAD/RA [3.02 (±0.70) versus 2.76 (±0.5) P < 0.054] but not significatively. Receiver operating characteristic curve analysis demonstrated optimal threshold to detect rupture at 2.8 for the ratio MAD/CTR (area under the curve (AUC) 0.593, sensitivity 47.4%, specificity 78.9%), at 3.3 for the ratio MAD/SMA (AUC 0.564, sensitivity 31.6%, specificity 92.1%), and at 3.3 for the ratio MAD/RA (AUC 0.591, sensitivity 31.6%, specificity 94.7%). Bivariate analysis for rupture risk factor showed significance for the three ratios (MAD/CTR > 2.8 [OR = 11 (1.42; 85.20) P < 0.0217], MAD/SMA > 3.3 [OR = 10 (1.28; 78.12) P < 0.0281], and MAD/RA >3.3 [OR = 11.00 (1.42; 85.20) P < 0.0217]). One scannographic sign was more present in the rupture group: crescent sign 36.8% versus 5.3%, P = 0.0007, as well in bivariate analysis [OR = 7 (1.59; 30.80) P < 0.0326]. CONCLUSIONS: In our experience, specific ratios when they exceed calculated threshold, seem to be more prone to rupture. We could consider that these measures, easy to apply in clinical practice, would be complementary keys for rupture risk individual assessment.

Ruptured Pancreaticoduodenal Artery Aneurysm due to a Median Arcuate Ligament Treated Solely by Revascularization of the Celiac Trunk.

Pancreaticoduodenal artery aneurysms (PDAAs) are rare, but rupture can occur at any time regardless of the size. We describe here the case of 53-year-old woman who presented with a ruptured PDAA associated with compression of the celiac trunk by the median arcuate ligament. We first performed revascularization of the celiac trunk without intervening on the PDAA because of surgically hostile conditions. We observed complete regression of the PDAA, probably due to the dramatic decrease in inflow to the PDAA, thanks to the revascularization procedure. This prompted us to cancel the secondary endovascular embolization. The patient remained asymptomatic at 3 months.