Stress Analysis of Aortic Vessels under Stent Graft / 医用生物力学

Objective To simulate the interaction between the stent graft (SG) and the aortic wall with finite element (FE) analysis by considering the influence of residual stress field, so as to study the stent influence on stress distributions of the aortic wall. Methods The three-dimensional (3D) residual stress field was generated in an idealized bi-layered thick-wall aortic model via a stress-driven anisotropic growth model by reducing the transmural stress gradient. Upon virtually deploying the SG, the stress on the aortic wall was calculated. Results The 3D residual stress field, corresponding to an opening angle of 117.5°, was shown to reduce the transmural stress gradient in both the circumferential and axial directions. The maximum stress was found at the contact area between aortic wall and wave peak of the stent. At 20% oversize ratio of the stent, the maximum stresses on the aortic wall in circumferential and axial direction were 412 and 132 kPa, respectively, while the in-plane shear stresses σrθ and σrz were both 78 kPa. Under residual stress, the maximum radial, circumferential and axial stresses were decreased by 14.9%, 40.5% and 33.8%, respectively, while the maximum shear stresses σrθ ，σrz，σθz were reduced by 2.5%, 7.1% and 27%, respectively. With the increase of oversize ratio from 10% to 20%, the maximum radial, circumferential and axial stresses were increased by 316%, 129% and 41%, respectively, while the maximum shear stresses σrθ ，σrz，σθz were increased by 661%, 450% and 466%, respectively. Conclusions The residual stress can effectively reduce the transmural stress gradient. Both the residual stress and the oversize ratio of the stent play an important role in modulating the wall stress distribution and the maximum stress.

Transcatheter closure of anastomotic leakage after surgical procedures for noninfected ascending aortic pathology / 中华放射学杂志

Objective To evaluate the safety and efficiency of transcatheter anastomotic leakage closure after surgical procedures for non-infected ascending aortic pathology with different occlusion devices. Methods From Dec. 2013 to Sep. 2015, six cases received interventional therapy for anastomotic leakage after surgical procedures for non-infected ascending aortic pathology using occluders. Four cases were with proximal graft-vessel anastomotic leakage, including two pseudoaneurysms at the site of aortic roots and two ascending aorta to right atrium shunts. The other two cases were with artificial grafts to intraoperative stent anastomotic leakage leading to endoleak type Ib. The anastomotic leakage was totally occluded by single ADOⅡrespectively in four cases. Two detachable coils were implanted in one case with artificial graft to intraoperative stent anastomotic leakage, but mild residual shunt to false lumen was detected by DSA and follow-up CTA. The second interventional procedure was carried out one month later, and one ADO Ⅱ was used to close the residual leakage totally. One PDA occluder was implanted along arteriovenous guide-wire track via aortic root to right atrium fistula in one case. Results All the anastomotic leakages of the six cases were totally excluded by different occlude devices percutaneously. The technical success rate was 100%. Follow-up time was from 1 month to 4 years. The patients' clinical condition improved obviously. Follow-up CTA showed no recurrence of anastomotic leakage. Complete thrombosis and marked shrinkage of the pseudoaneurysm were achieved in two cases, and the partial thrombosis and shrinkage of the false lumen were achieved in 2 cases. Conclusion Trans-catheter closure is an alternative treatment for ascending aortic surgical anastomotic leakage, which may achieve satisfactory short-and mid-term results.

Efficacy of personalized endovascular repair using two stent-grafts for patients with Stanford B aortic dissection / 中华心血管病杂志

<p><b>OBJECTIVE</b>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).</p><p><b>METHODS</b>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.</p><p><b>RESULTS</b>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).</p><p><b>CONCLUSIONS</b>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.</p>

Clinical analysis of modiifed transcatheter closure of atrial septal defect in 100 cases PU / 中国介入心脏病学杂志

Objective To summraize the safety and efifcacy of modiifed transcatheter closure of atrial septal defect. Methods From Dec. 2012 to Dec. 2013, 100 cases performed modiifed transcatheter closure of atrial septal defect in our center (72 were famale and 28 were male) with average age (37±16) years. The diagnosis was conifrmed by transthoracic echocardiography. All the atrial septal defect closures were completed in the modiifed way by direct delivery of the closure devices without the need of guidence wire. Results One hundred and one defects were identiifed in 100 patients, with 1 patient had 2 defects. The mean diameter of the defect was (20.3±6.6) mm. 100 devices were implanted successfully. Complete closure was revealed in all the patients after the procedure. One patient developed atrial ifbrillation during the procedure. No other serious complication occurred till the last follow-up. Conclusions The modiifed transcatheter closure of atrial septal defect is an effective procedure with high successful rate and low rate of complications.