A non-invasive methodology for ATAA rupture risk estimation.

Ascending thoracic aortic aneurysms (ATAA) are a life-threatening pathology provoking an irreversible dilation with a high associated risk of aortic rupture or dissection and death of the patient. Rupture or dissection of ATAAs remains unpredictable and has been documented to occur at diameters less than 4.5 cm for nearly 60% of patients. Other factors than the aneurysm diameter may highly affect the predisposition to rupture. In order to have a better insight in rupture risk prediction, a bulge inflation bench was developed to test ATAAs samples collected on patients during surgical interventions. Preoperative dynamic CT scans on a cohort of 13 patients were analyzed to estimate volumetric and cross-sectional distensibility. A failure criteria based on in vitro ultimate stretch showed a significant correlation with the aortic membrane stiffness deduced from in vivo distensibility. These results reinforce the significance of stretch-based rupture criteria and their possible non-invasive prediction in clinical practice.

Fluid- and Biomechanical Analysis of Ascending Thoracic Aorta Aneurysm with Concomitant Aortic Insufficiency.

We present a comprehensive and original framework for the biomechanical analysis of patients affected by ascending thoracic aorta aneurysm and aortic insufficiency. Our aim is to obtain crucial indications about the role played by deranged hemodynamics on the ATAAs risk of rupture. Computational fluid dynamics analysis was performed using patient-specific geometries and boundary conditions derived from 4D MRI. Blood flow helicity and wall shear stress descriptors were assessed. A bulge inflation test was carried out in vitro on the 4 ATAAs after surgical repair. The healthy volunteers showed no eccentric blood flow, a mean TAWSS of 1.5 ± 0.3 Pa and mean OSI of 0.325 ± 0.025. In 3 aneurismal patients, jet flow impingement on the aortic wall resulted in large TAWSS values and low OSI which were amplified by the AI degree. However, the tissue strength did not appear to be significantly reduced. The fourth patient, which showed the lowest TAWSS due to the absence of jet flow, had the smallest strength in vitro. Interestingly this patient presented a bovine arch abnormality. Jet flow impingement with high WSS values is frequent in ATAAs and our methodology seems to be appropriate for determining whether it may increase the risk of rupture or not.

Editor's Choice - Ex vivo Renal Artery Repair with Kidney Autotransplantation for Renal Artery Branch Aneurysms: Long-term Results of Sixty-seven Procedures.

OBJECTIVE/BACKGROUND: To evaluate the long-term outcome of renal revascularization by ex vivo renal artery reconstruction and autotransplantation for renal artery branch aneurysms (RABAs). METHODS: Between 1991 and 2015, 67 ex vivo renal artery reconstructions with kidney autotransplantation were performed in 55 adults (mean age 47 years) and 10 children to repair 87 RABAs. The main underlying disease was fibromuscular dysplasia in 34 patients. Other etiologies were systemic congenital disease in eight patients, spontaneous dissecting aneurysms in five, iatrogenic aneurysms in three, atheromatous aneurysms in two and unknown etiology in 13. Median RABA diameter was 20.5 mm. Fifty-three patients (82%) were hypertensive, 60 had normal renal function and no patient was on hemodialysis. Seven patients (11%) were operated on after failure of an endovascular procedure. The mean number of renal artery branches repaired per patient was 3.5 and multiple aneurysms were treated in 14 patients (22%). The hypogastric artery was used in 41 patients, the saphenous vein in 18, the superficial femoral artery in five and a combination of different materials in three. RESULTS: No deaths occurred during the first 30 days. Primary patency at 30 days was 90.8% following to six early thromboses. Three patients (5%) were lost to follow up. No other thrombosis occurred. At 8 years, the primary and primary-assisted patency were 88% and 91%, respectively. Survival was 95% at 9 years. Among the 53 hypertensive patients, two were lost to follow up. At 9 years, 22 (43%) were cured and nine (18%) were improved with a significant reduction of antihypertensive medication (p < .05). The pre-operative modification of the diet in renal disease (MDRD) clearance was 93 ± 29 mL/minute, the immediate post-operative MDRD was 94 ± 33 mL/minute, and at the end of follow up it was 86 ± 26 mL/minute (p > .05). CONCLUSION: Ex vivo renal artery reconstruction for complex RABAs eliminates the risk of rupture, confers a benefit to hypertension, and preserves renal function with a satisfactory long-term patency.

Common hepatic artery as inflow in kidney transplantation.

Kidney transplantation originating from the hepatic artery has not previously been reported. Herein, we report a third kidney transplantation with the common hepatic artery as inflow. A 62-year-old male with chronic renal failure due to polycystic kidney disease was proposed to a third kidney transplantation. CT-scan showed diffuse calcification of the aorto-iliac axis and the splenic artery. The common hepatic artery was the only artery suitable for anastomosis and as such was chosen as the inflow for retransplantation. The operation was performed through a right subcostal laparotomy. A saphenous bypass was interposed between the common hepatic artery and the graft, then the renal vein was anastomosed to the suprarenal inferior vena cava. Duration of warm ischemia was 27 min. Postoperative course was complicated with delayed graft function of 17 days and pulmonary infection. Patient was discharged at day 30. With a follow-up of 40 months, serum creatinine level and eGFR are, respectively, 191 µmol/L and 32 mL/min. Hepato-renal bypass technique can be used in kidney retransplantation when patient anatomy is not compatible with other classical options.

Experimental foundation for in vivo measurement of the elasticity of the aorta in computed tomography angiography.

OBJECTIVE: This study was performed to determine the feasibility of measuring the elastic properties of the arterial wall in vivo. To prove this concept, elastic parameters were calculated from an aortic model of elastic behavior similar to a human aorta using computed tomography angiography (CTA) images. METHODS: We first constructed an aortic model from polydimethylsiloxane (PDMS). This model was inserted into a pulsatile flow loop. The model was then placed inside a computed tomography scanner. To estimate the elasticity values, we measured the cross-sectional area and the pressure changes in the model during each phase of the simulated cardiac cycle. A discrete wavelet transform (DWT) algorithm was applied to the CTA data to calculate the geometric changes in the pulsatile model over a simulated cardiac cycle for various pulsatile rates and elasticity values of the PDMS material. The elastic modulus of the aortic model wall was derived from these geometric changes. The elastic moduli derived from the CTA data were compared with those obtained by testing strips of the same PDMS material in a tensile testing machine. Our two aortic models had elastic values at both extremes of those found in normal human aortas. RESULTS: The results show a good comparison between the elastic values derived from the CTA data and those obtained in a tensile testing machine. In addition, the elasticity values were found to be independent of the pulsatile rate for mixing ratios of 6:1 and 9:1 (p = .12 and p = .22, respectively). CONCLUSIONS: The elastic modulus of a pulsatile aortic model may be measured by electrocardiographically-gated multi-detector CTA protocol. This preliminary study suggests the possibility of determining non-invasively the elastic properties of a living, functioning aorta using CTA data.

Early and late results of ex vivo repair and autotransplantation in solitary kidneys.

INTRODUCTION: Autotransplantation of a solitary kidney provides an excellent opportunity to study the immediate and long-term consequences of intra-operative renal ischaemia. The purpose of this report is to describe a series of nine patients who underwent ex vivo repair and autotransplantation on solitary kidneys. PATIENTS AND METHODS: The series included six females and three males with a mean age of 36 years. Seven of the nine patients were hypertensive (mean number of anti-hypertensive agents: 3). Two patients had chronic renal failure (serum creatinine levels: 192 and 205 µmol l(-1)). All arteries except one with Takayasu disease were affected by dysplastic aneurysm or fibrodysplasia lesion. There was no atherosclerotic lesion. The mean number of renal artery branches repaired was 3.1 per patient. Mean duration of ischaemia was 161 min. RESULTS: Creatinaemia increased in all patients following the procedure. Creatinaemia and clearance returned to preoperative values between the 3rd and 10th postoperative days. One kidney was lost due to renal vein thrombosis. Late findings indicated that renal function was stable and there was no deterioration in the function of the autotransplanted kidneys after a follow-up period of 89 months. Preoperative versus postoperative creatinaemia and clearance levels were respectively 111 vs. 105 µmol l(-1) and 66.9 vs. 62.0 ml min(-1) (ns). During the same time, the mean number of anti-hypertensive agents decreased slightly from 3 to 2.5. CONCLUSION: In this small series of patients who underwent ex vivo repair and autotransplantation on solitary kidneys, intra-operative renal ischaemia had no detrimental effect on renal function.

[Focal atherosclerotic abdominal aortic stenosis]. / Sténose médio-aortique d'origine athéroscléreuse.

We report a case of a 54-year-old woman presenting a symptomatic focal atherosclerotic abdominal aortic stenosis. Computed tomographic angiography allowed to study the lesion, the abdominal aorta and its main branches. The patient was treated via an endovascular approach using a covered stent. The postoperative course was uneventful and the patient was asymptomatic with a patent reconstruction after 18 months. Improvement in endovascular technology has totally modified the treatment of focal atherosclerotic abdominal aortic stenosis. However, many technical points remain to be determined including the necessity of systematic stenting, the type of stent to use, and the steps of the procedure.

In vitro characterisation of physiological and maximum elastic modulus of ascending thoracic aortic aneurysms using uniaxial tensile testing.

OBJECTIVE: Ascending thoracic aortic aneurysms (ATAA) are a life-threatening condition due to the risk of rupture or dissection. This risk is increased in the presence of a bicuspid aortic valve (BAV). The purpose of this study was to provide data on the elastic modulus of aortic wall of ATAA using uniaxial tensile testing in two different areas of the stress-strain relationship: physiological and maximum range of stresses. The influence of tissue location, tissue orientation and valve type on these parameters was investigated. MATERIALS AND METHODS: Tissues freshly excised from ATAA with bicuspid or tricuspid aortic valve were obtained from greater and lesser curvature (GC and LC) and the specimens were tested uniaxially in circumferential (CIRC) and longitudinal (LONG) orientation. Maximum elastic modulus (MEM) was given by the maximum slope of the stress-strain curve before failure. Physiological modulus (PM) was derived from the Laplace law and from ranges of pressure of 80-120 mmHg. Means of each group of specimen were compared using Student's t-test to assess the influence of location, orientation and valve type on each mechanical parameter. RESULTS: PM was found to be significantly lower than the MEM (p < 0.001). The MEM and PM were significantly higher (p < 0.01) in the CIRC (n = 66) than in the LONG orientation (n = 42). The MEM was higher in the circumferential orientation in the BAV group (p < 0.001 in GC and p < 0.05 in LC). MEM and PM in GC specimens were higher in the longitudinal orientation than the LC specimens (p < 0.05). CONCLUSION: This study demonstrates the anisotropy of the aortic wall in ATAA and provides data on the mechanical behaviour in the physiological range of pressure.

Bypass to the perigeniculate collateral arteries: mid-term results.

PURPOSE: The purpose of this report is to present mid-term results of infrainguinal revascularizations using either the highest genicular artery or medial sural artery as the distal anastomosis site. MATERIAL AND METHODS: Between 1996 and 2005, a total of 59 bypass procedures to perigeniculate collateral arteries were performed in 57 patients (14 women, 43 men) with a mean age of 74. Fifty five patients presented with critical ischemia (tissue loss in 28 and rest pain in 27). Four patients presented with intermittent claudication. Mean ankle brachial index was 0.48. The distal anastomosis site was the highest genicular artery in 18 patients, medial sural artery in 37 cases, highest genicular and/or medial sural artery and/or tibial artery in sequential fashion in four cases. The proximal anastomosis was to the common femoral artery in 26 cases and superficial femoral artery in 33. RESULTS: There were two deaths during the immediate postoperative period. Mean follow-up duration was 35 months (range 1-108 months). One patient was lost to follow-up. Six patients required major amputation. At 3 years, primary patency was 65+/-7%, secondary patency was 70+/-7%, limb salvage and survival rate were 90+/-4% and 64+/-7% respectively. CONCLUSION: Bypass to perigeniculate collateral arteries provides acceptable patency and limb salvage rates.