Animal experimental study on the effects of different levels of amputation on cardiovascular system / 生物医学工程学杂志

Vascular injury resulting from lower limb amputation leads to the redistribution of blood flow and changes in vascular terminal resistance, which can affect the cardiovascular system. However, there was no clear understanding of how different amputation levels affect the cardiovascular system in animal experiments. Therefore, this study established two animal models of above-knee amputation (AKA) and below-knee amputation (BKA) to explore the effects of different amputation levels on the cardiovascular system through blood and histopathological examinations. The results showed that amputation caused pathological changes in the cardiovascular system of animals, including endothelial injury, inflammation, and angiosclerosis. The degree of cardiovascular injury was higher in the AKA group than in the BKA group. This study sheds light on the internal mechanisms of amputation's impact on the cardiovascular system. Based on the amputation level of patients, the findings recommend more comprehensive and targeted monitoring after surgery and necessary interventions to prevent cardiovascular diseases.

Effect of lower limb amputation level on aortic hemodynamics: a numerical study / 生物医学工程学杂志

It has been found that the incidence of cardiovascular disease in patients with lower limb amputation is significantly higher than that in normal individuals, but the relationship between lower limb amputation and the episodes of cardiovascular disease has not been studied from the perspective of hemodynamics. In this paper, numerical simulation was used to study the effects of amputation on aortic hemodynamics by changing peripheral impedance and capacitance. The final results showed that after amputation, the aortic blood pressure increased, the time averaged wall shear stress of the infrarenal abdominal aorta decreased and the oscillatory shear index of the left and right sides was asymmetrically distributed, while the time averaged wall shear stress of the iliac artery decreased and the oscillatory shear index increased. The changes above were more significant with the increase of amputation level, which will result in a higher incidence of atherosclerosis and abdominal aortic aneurysm. These findings preliminarily revealed the influence of lower limb amputation on the occurrence of cardiovascular diseases, and provided theoretical guidance for the design of rehabilitation training and the optimization of cardiovascular diseases treatment.

Biomechanical Issues in COVID-19 Epidemic / 医用生物力学

Corona virus disease 2019 (COVID-19) has been the focus of global attention since its outbreak. With the rapid spreading of COVID-19, serious challenges including medical management system, medical resources, emergency response, medical devices and instruments gradually occur, revealing many shortcomings among these aspects. Herein, through the principles, viewpoints and methods of biomechanics, this article recognizes and analyzes the existing problems that are urgently needed to be solved, such as the study of in-vitro viability of the virus, the biomechanics of aerosol, the fluid mechanics in public transportation and places, the relationship between respiratory diseases and cardiovascular diseases, the improvement of medical devices, with an objective of taking advantages of biomechanics in epidemic prevention and control, so as to promote the development of biomechanics.

Stent graft coverage of dual-stent strategy in the management of abdominal aortic aneurysms.

Treating an abdominal aortic aneurysm (AAA) with a stent graft (SG) and a multilayer stent (MS) is a key technology in isolating flow fields. Clinically, dual stents (an SG in the proximal and an MS in the distal of AAA) are used for treatment of AAA, but only a few studies have examined the relationship between SG coverage and treatment effects. Through numerical simulation of the hemodynamics after SG and MS implantation, the SG coverage and position were simulated at 0% (0 mm), 25% (13.75 mm), 50% (27.5 mm), and 75% (41.25 mm). With increasing SG coverage, the pressure on the aneurysm sac wall and the flow of branch vessels gradually decreased, and the lower wall shear stress (WSS) gradually increased. The changes in pressure, lower WSS, and the mass flow rate of the branch vessels did not change significantly. The coverage of the SG has a nonsignificant effect on hemodynamics in the treatment of AAA; the implantation position need not be very precise. This research can provide theoretic support for clinicians' decision-making.

Investigation of the hemodynamics of a juxtarenal aortic aneurysm with intervention by dual-stents strategy.

OBJECTIVE: To study the feasibility of using two stents (a combination of multilayer stent [MS] and stent graft [SG]) in the treatment of a juxtarenal aortic aneurysm that involves a significant branch artery and to determine the advantages and disadvantages of using SGs upstream and downstream from the aneurysm so as to provide some theoretical guidance for preoperative clinical decision-making in the future. METHODS: Four ideal geometric models were established for numerical computation: case 1 refers to an aneurysm without the use of stents, case 2 represents the implantation of two MSs in an aneurysm, and case 3 (SG + MS) and case 4 (MS + SG) both involve the treatment of an aneurysm by using a combination of SG and MG. RESULTS: The aneurysm pressure is slightly lower and there are more vortices when the SG is implanted (case 3 and case 4). In particular, for case 4, additional vortices appear in the sac and the area of the low-wall shear stress is larger on the aneurysm compared with those of the other three cases. However, the pressure becomes uneven, and a peak pressure region is observed on the wall of the aneurysm, and therefore, the aneurysmal wall will become buckled. In addition, the flux of the renal artery in the four cases is greater than that in the normal case. CONCLUSION: The arrangements in cases 3 and 4 can effectively isolate the aneurysm from circulation, but clinically, it is necessary to avoid such a high-risk situation wherein the SG is positioned downstream of the aneurysm (case 4), even though this leads to improved isolation.

Hemodynamic Analysis of Stanford Type B Aortic Dissection Based on Computational Fluid Dynamics / 医用生物力学

Objective To analyze the hemodynamic parameters of Stanford type B aortic dissection based on computational fluid dynamics (CFD), so as to make a thorough evaluation of the disease.Methods Based on CTA images of a patient with complex Stanford type B aortic dissection, the three-dimensional model and hemodynamic numerical simulation were carried out to analyze the velocity distribution of flow field and intersecting fracture profile, as well as the wall shear stress. Results The maximum velocity of blood flow at the entry tear and re-entry tear could reach 1.2 m/s and 2 m/s, respectively, providing references for further evaluation on aortic rupture position and prediction of aortic rupture risk. An obvious low wall shear stress zone was formed on false lumen wall near the entry tear, which was consistent with the thrombus position in the patient. Conclusions CFD could effectively analyze the hemodynamic characteristics of complex aortic dissection, obtain the correlation between aortic dissection and wall shear stress at aorta arch and descending aorta, which contributed to guiding clinical assessment of aortic function for preventing the diseases.

The effect of p53mut,P53wt and p16 on the expression of Smad4 in lung cancer H1299 cells / 临床外科杂志

Objective To investigate the influence of exogenous p53mut, p53wt and p16 on the expression of Smad4 in lung cancer H1299 cells. Methods Target genes (p53mut, p53wtand p16) were amplified by PCR and inserted into effective eukaryotic expression vector pIRES2-EGFP, respectively. These recombinant plasmids were transfected into H1299 cells by lipofectamine. The fluorescence microscope was employed to observe the transfected cells and the expression of EGFP. RT-PCR was used to validate the transfection efficiency. Western blot assay was used to detect the change of the Smad4 expression in H1299, Results Green fluorescence was observed under fluorescence microscope in the transfected H1299 cells at 72 hour post transfection. RT-PCR indicated that p53mut, p53wt and p16 genes were highly expressed in H1299 cell. There was no significant difference in Samd4 expression between the empty plasmid group and control group(P＞0.05). But the expression of Samd4 in p53mut transfected group was decreased(P＜0.05). On the contrary, the expression of Smad4 was increased in the p53wt transfected group and P53wt and p16 co-transfected group. Moreover, the increase was more obvious in the P53wt and p16 cotransfected group(P＜ 0.05). Conclusion P53mut gene transfection reduces the expression of Smad4 and P53wt. The co-infection of p53mut and p16 increases the expression of Smad4 in the H1299 cells. The tumor promoting effect of p53mut and the antitumor effect of p53

Influencing factors on informed consent for primary percutaneous coronary intervention in patients with acute ST-segment elevation myocardial infarction / 中国介入心脏病学杂志

Objective To determine the influencing factors on informed consent associated with decline or delay of primary percutaneous coronary intervention (PCI) in patients with acute ST-segment elevation myocardial infarction(STEMI).Methods This study was conducted in Peking University People′s Hospital from 1 August, 2014 to 31 March, 2016, with 229 consecutive cases of acute STEMI enrolled in the study.Data were collected by reviewing medical records and STEMI treatment time records.180 patients with ischemic symptoms ≤12 hours were included in the final analysis.Patients were divided into the consent group and the refusal group according to the final decision.For patients who received primary PCI, they were further categorized into two groups based on the 30min cut-off time.Results Among the 180 STEMI patients reviewed, 139 patients agreed to primary PCI and the remaining 41 patients refused primary PCI.Multivariate logistic analysis showed that symptom relief (OR 5.532, 95% CI 1.165-26.278, P=0.031) and history of chronic kidney disease (OR 4.786, 95% CI 1.346-17.011, P=0.016) were predictors of dissent of primary PCI.Self-rated symptoms severity (OR 0.094, 95% CI 0.034-0.260, P<0.001)was predictor of consent to primary PCI.106 patients had complete time point records of informed consent in the consent group (n=139).Among these patients, the median informed consent delay was 24 min.64 patients made a decision within 30 minutes, and the other 42 patients had their decision made beyond 30 minutes.Symptom-to-door time ≥4 hours (OR 4.563,95% CI 1.682-12.385, P=0.003) was independent predictor of informed consent delay.Conclusions Patients with resolved symptoms, self-rated mild symptoms or renal insufficiency were more inclined to refuse primary PCI.For patients who eventually received primary PCI, symptom-to-door time ≥4 hours was the independent predictor of informed consent delay.