Endovascular repair of Stanford B aortic dissection using two stent grafts with different sizes.

OBJECTIVE: The objective of this study was to introduce a novel strategy for thoracic endovascular aortic repair of Stanford B aortic dissection using two-stent graft implantation (TSI), in which the proximal stent and distal stent with different sizes are sequentially deployed, and to summarize our experience with this technique. METHODS: A retrospective study was conducted of 72 consecutive patients (61 men; mean age, 55 ± 7 years; range, 41-67 years) with Stanford type B aortic dissection who underwent TSI treatment between January 2012 and May 2013. Among all patients, 43 (59.7%) involved the infrarenal aorta and 29 (40.3%) involved the whole thoracic and abdominal aorta; mean aortic involvement length was 226 ± 13 mm (range, 182-312 mm). Eight cases were for acute dissection (within 2 weeks from onset of symptoms), 11 cases were for chronic dissection (>3 months after initial dissection), and 53 cases were for subacute dissection (between 2 weeks and 3 months). Twenty-two cases (30.6%) were uncomplicated type and 50 cases (69.4%) were complicated type. Follow-up was performed postoperatively at 1 month, 6 months, and yearly thereafter. Technique success, aorta morphology, and procedure-related complications were evaluated. RESULTS: Technical success was achieved in 100%; 72 pairs of stent grafts (144 thoracic stent grafts) and 10 left subclavian artery chimney stents were used. The mean aortic length coverage by the stent grafts was 197.6 ± 20.3 mm, and mean taper diameter span was 7.5 ± 1.8 mm. All patients were followed up from 6 to 16 months (mean, 10 ± 4 months); 95.8% (69 of 72) had a thrombosed false lumen in the aortic coverage, and the true lumen expanded on average 57% ± 11% (23%-100%). No significant changes were found in aortic diameters of the proximal and distal ends of the two stent grafts and the angles between centerlines of the distal end of the stent and the aorta during follow-up. Procedure-related complications included transient paraplegia (coverage of the left subclavian artery without revascularization and extensive coverage of aorta >220 mm) due to acute spinal cord ischemia (n = 1) and malapposition of the distal stent (primary tear closed, true lumen expansion led to oversize rate insufficient in distal stent diameter; n = 1). No death or malperfusion complications were observed during the perioperative period and follow-up. CONCLUSIONS: Short-term outcomes showed TSI to be a flexible and effective approach to accurately repair Stanford B aortic dissection that could potentially address the limitations of currently available stent grafts. Further prospective clinical studies are warranted to evaluate its long-term efficacy.

Endovascular repair of abdominal aortic aneurysm with severely angulated neck and tortuous artery access: case report and literature review.

BACKGROUND: Endovascular aneurysm repair has revolutionized the therapeutic strategy for abdominal aortic aneurysm. However, hostile proximal aneurysmal neck and tortuosity of access vessels remain challenges in selecting optimal stent-grafts in abdominal aortic aneurysms with difficult anatomy. CASE PRESENTATION: A 65-year-old woman complained of intermittent abdominal pain for one week. Computed tomography angiogram demonstrated a tortuous infrarenal abdominal aortic aneurysm with a tapered neck and a 136° of infrarenal angulation. Aneurysmal dilatation and severe calcification of bilateral iliac arteries and tortuous aortoiliac access were also showed. Endovascular approach using Endurant stent-graft was attempted at an outside hospital, but failed because of the significant tortuosity of the abdominal aorta and iliac arteries. Since the patient refused to have open aneurysm repair, he was transferred to our hospital for further evaluation and possible EVAR with a different approach. EVAR was performed successfully using Gore Excluder stent-grafts (W.L. Gore & Associates, Flagstaff, AZ, USA). During the procedure, cannulation of the contralateral limb was unable to be achieved because of the tortuous aortoiliac course. Therefore, a snare was inserted from right radial artery, through the contralateral gate, to grasp the wire from left femoral artery. Two iliac stent-grafts were sequentially deployed with the lower end distal to the opening of the left internal iliac artery. Angiography confirmed complete sealing of the aneurysm with patency of bilateral renal arteries and external iliac arteries. The postoperative courses were uneventful and follow-up computed tomography angiogram at 6 months demonstrated patent bilateral femoral and renal arteries without endoleaks or stent migration. CONCLUSION: Although endovascular repair of aortic aneurysm with hostile neck and tortuous access is rather challenging, choosing flexible stent-grafts and suitable techniques is able to achieve an encouraging outcome.

[Efficacy of personalized endovascular repair using two stent-grafts for patients with Stanford B aortic dissection].

OBJECTIVE: To observe the feasibility and clinical efficacy of thoracic endovascular aortic repair (TEVAR) for patients with Stanford B aortic dissection using personalized two stent-grafts implantation (TSI). METHODS: This retrospective review included 56 patients who underwent TSI during TEVAR for Stanford B aortic dissection from Jan 2012 to May 2013 in Beijing Anzhen hospital. There were 8 patients in acute phase (within 2 weeks from onset of symptoms), 11 patients in chronic phase (greater than 2 months following initial dissection) and 37 patients in subacute phase (between 2 weeks and 2 months from onset of symptoms). Infrarenal aorta was involved in 34 patients (60.7%) and suprarenal aorta involved in 22 patients (39.3%), the mean aortic lesion length was (226 ± 13)mm. Thoracic and abdominal aortic angiography was performed during operation to measure aortic diameters of proximal and distal landing zone, and the distance between them. The proximal stent-grafts were implanted in distal aorta to the origin of left subclavian artery with oversize rate of 10%-15% according to proximal landing zone according to procedural guideline. Then the distal newly customized large tapered stent-grafts were sequentially deployed according to the diameters of both the distal end of proximal stent and distal landing zone (aortic true lumen), and overlapping length of the two stent-grafts was more than 30 mm. Patients were followed-up at 3 months, 6 months, and yearly thereafter post operation. RESULTS: TSI procedure was successful in all patients and 122 stent-grafts were implanted. The mean length of implanted stent-grafts was (197.6 ± 20.3)mm. The mean diameter taper span was (7.5 ± 1.8)mm with proximal oversize rate of (12.8 ± 3.4)% and distal oversize rate of (11.2 ± 4.1)%. The mean angle between the distal end of stent and aorta was (2.3 ± 1.3)°. The diameter of proximal and distal landing zone, and angle between the distal end of stent and aorta remained unchanged during follow up (mean: (10.0 ± 4.0) months). The total thrombosis rate of the false lumen was 98.2% (55/56), thrombosis rate of stent segment was 82.1% (46/56) . Stent-related complications were observed in 2 patients (3.6%) , including acute spinal cord ischemia due to paraplegia (n = 1) and malposition of distal stent (n = 1). CONCLUSIONS: Encouraging short-term outcomes are obtained from current personalized two stent-grafts implantation strategy for patients with Stanford B aortic dissection. Further prospective clinical studies are warranted to evaluate the long-term efficacy of this procedure.

Experimental Study on the Dilatancy and Energy Evolution Behaviors of Red-Bed Rocks under Unloading Conditions.

Surrounding rock deformation and consequent support failure are the most prominent issues in red-bed rock tunnel engineering and are mainly caused by the effects of unloading, rheology, and swelling. This study investigated the mechanical responses of two kinds of red-bed mudstone and sandstone under unloading conditions via laboratory observation. Volume dilation was observed on the rocks during unloading, and the dilatancy stress was linear with the initial confining pressure. However, the ratios of dilatancy stress to peak stress of the two rocks kept at a range from 0.8 to 0.9, regardless of confining pressures. Both the elastic strain energy and the dissipated energy evolved synchronously with the stress-strain curve and exhibited conspicuous confining pressure dependence. Special attention was paid to the evolution behavior of the dilatancy angle. The dilatancy angle changed linearly during unloading. When the confining pressure was 10 MPa, the dilatancy angle of mudstone decreased from 26.8° to 12.5° whereas the dilatancy angle of sandstone increased from 34.6° to 51.1°; when the confining pressure rose to 25 MPa, the dilatancy angle of mudstone and sandstone decreased from 45.8° to 17.4° and increased from 21.7° to 39.5°, respectively. To further understand the evolution of the dilatancy angle, we discussed the links between the variable dilatancy angle and the processes of rock deformation and energy dissipation.