Numerical Simulation of In-Plane Crack Propagation in Aortic Dissection / 医用生物力学

Objective Based on interface damage, a numerical simulation method for in-plane propagation of false lumen (FL) was proposed to explore the regular pattern of in-plane propagation of the initial cavity. Methods Three interface damage modes were characterized by bi-linear traction separation law, and the damage parameters were calibrated by simulating peeling and shearing tests. The damage interface was introduced into the ideal double-layer cylindrical tube aortic model by means of cohesive zone model (CZM) to simulate the in-plane propagation of FL. The control variable method was used to establish several computational models to investigate the influence of cavity geometric parameters on propagation direction, critical pressure and interface damage mode. Results The interface damage was mainly opening mode (Mode I) in axial propagation and sliding mode (Mode II) in circumferential propagation. With radial depth of the initial cavity increasing, the propagation of the FL changed from circumferential direction to axial direction, the critical pressure decreased, and the axial damage tended to be pure opening mode. With circumferential angle and axial length of the initial cavity increasing, the critical pressure decreased and the circumferential damage tended to be pure sliding mode. The critical pressure of single damage was lower than that of mixed damage. Conclusions The CZM can effectively characterize interface damage behavior of elastic lamellae within the media, and it applies to numerical simulation of in-plane propagation of the FL. The results of this study is helpful to understand the complex pathophysiological process of dissection crack propagation.

Clinical outcomes of severe calcified lesions after carotid artery stenting / 中华普通外科杂志

Objective:To evaluate the safety and efficacy of carotid artery stenting (CAS) in the treatment of non-circumferential severe calcification using the distal embolic protection device.Methods:Clinical data of patients with severe calcification lesions in cervical carotid artery treated by CAS from Jan 2018 to Dec 2020 at our center was analyzed retrospectively.Results:226 consecutively admitted patients of cervical carotid artery stenosis and non-circumferential severe calcification (CR>270°) underwent CAS using the distal embolic protection device. The technical success rate was 90.26%. No death or myocardial infarction occurred during the perioperative period. Two patients had ipsilateral hemiparesis ischemic stroke during post-dilatation. The incidence of perioperative bradycardia/hypotension was 25.34%. Patients were followed up for 6-36 months, with median follow-up period of 17.3 months. The incidence of mild or moderate in-stent restenosis (<70%) was 16.59%, and the incidence of severe in-stent restenosis or occlusion (>70%) was 3.22%.Conclusions:For carotid artery stenosis with non-circumferential severe calcification in high risk for CEA patients, carotid artery stenting is safe and effective with the aggressive pre-dilation strategies, strict stent selections and implantation standards. The incidence of perioperative death, myocardial infarction or ipsilateral hemiparesis ischemic stroke was low. The patency rate of the carotid stent in the calcification lesion is satisfactory during the mid-term follow-up.

Research on injection flow velocity planning method for embolic agent injection system / 生物医学工程学杂志

Interventional embolization therapy is widely used for procedures such as targeted tumour therapy, anti-organ hyperactivity and haemostasis. During embolic agent injection, doctors need to work under X-ray irradiation environment. Moreover, embolic agent injection is largely dependent on doctors' experience and feelings, and over-injection of embolic agent can lead to reflux, causing ectopic embolism and serious complications. As an effective way to reduce radiation exposure and improve the success rate of interventional embolization therapy, embolic agent injection robot is highly anticipated, but how to decide the injection flow velocity of embolic agent is a problem that remains to be solved. On the basis of fluid dynamics simulation and experiment, we established an arterial pressure-injection flow velocity boundary curve model that can avoid reflux, which provides a design basis for the control of embolic agent injection system. An in vitro experimental platform for injection system was built and validation experiments were conducted. The results showed that the embolic agent injection flow speed curve designed under the guidance of the critical flow speed curve model of reflux could effectively avoid the embolic agent reflux and shorten the embolic agent injection time. Exceeding the flow speed limit of the model would lead to the risk of embolization of normal blood vessels. This paper confirms the validity of designing the embolic agent injection flow speed based on the critical flow speed curve model of reflux, which can achieve rapid injection of embolic agent while avoiding reflux, and provide a basis for the design of the embolic agent injection robot.

Endovascular treatment of popliteal artery aneurysm in a clinical analysis of 9 cases / 中华外科杂志

<p><b>OBJECTIVE</b>To evaluate the efficacy of endovascular repair of popliteal artery aneurysm (PAA) and to summarize the clinical experience and lessons.</p><p><b>METHODS</b>A clinical data of 9 PAA cases (males 8, females 1, age range 55-84) undergoing endovascular repair from October 2006 to December 2014 at Zhongshan Hospital Fudan University were retrospectively analyzed. CT angiography was made in all of the 9 cases preoperatively, and 10 PAA were included in the analysis. Of the 9 cases, 6 cases were symptomatic. The mean diameter of PAA was 3.9 cm (range, 2.1-8.2).</p><p><b>RESULTS</b>The technique successful rate of endovascular repair was 10/10. The preoperative complications were 2/10, including one case suffered hematoma in the arterial puncture site and 1 case with distal artery embolization. The mean follow-up was 33 months (range, 3-87). During the follow-up, 2 cases received the secondary intervention and drug thrombolysis because of the stent distal thrombosis. The stent-graft primary patency at 1 year was 78.8% (95% CI: 48%-91%). One case suffered stent fracture, and one case died of brainstem hemorrhage 15 months post endovascular repair of PAA.</p><p><b>CONCLUSIONS</b>Endovascular treatment of PAA is safe and effective in perioperative and midterm follow-up. However, individual endovascular strategy and postoperative complications in the long-term follow-up should be payed more attention.</p>

Clinical analysis of hybrid treatment for extensive aortic disease / 中华外科杂志

<p><b>OBJECTIVE</b>To evaluate the effect of extensive aortic diseases (EAD) after hybrid repair with supra-arch branches or visceral arterial debranching and endovascular repair.</p><p><b>METHODS</b>A total of 24 EAD patients (19 male and 5 female) underwent hybrid repair in Department of Vascular Surgery, Zhongshan Hospital, Fudan University between March 2005 and April 2015. The clinical data was analyzed retrospectively. The mean age was (49±12) years (from 29 to 69 years). The high-risk candidates for open surgery were enrolled in the study. The patients, including 14 cases with thoracic aortic aneurysms and 10 cases with aortic dissection, were treated by one or two stages. Post-operative follow-up with CT angiography was performed at 3, 6 and 12 months and then annually thereafter.</p><p><b>RESULTS</b>A total of 74 branches, including 63 with visceral arteries and 11 with supra-arch arteries, were recanalized. Nine patients were treated in two-stage hybrid procedure and fifteen were repaired by one stage. The perioperative mortality was 12.5% (3/24), whereas the aneurysm-related mortality was 8.3% (2/24). The 30-day patency of the grafts was 95.9% (71/74). There was no endoleak, paralysis, and intestinal ischemia at 30 days post-hybrid procedures. Four cases (16.6%) suffered acute renal dysfunction. During the follow-up (3 to 123 months), there were two deaths and one endoleak (type Ia and III) which emerged at 4 months post-procedure. The 1-year and 3-year survival rates were 81.7% and 73.5%, respectively.</p><p><b>CONCLUSIONS</b>Hybrid treatment is safe and effective for complex EAD patients in the midterm follow-up. It is especially suitable for the high-risk patients with comorbidities, re-intervention, or little tolerance to open surgery repair.</p>