Characterization of the dynamic viscoelastic response of the ascending aorta imposed via pulsatile flow.

This study characterizes the material properties of a viscoelastic, ex vivo porcine ascending aorta under dynamic-loading conditions via pulsatile flow. The deformation of the opaque vessel wall and the pulsatile flow field inside the vessel were recorded using ultrasound imaging. The internal pressure was extracted from the pulsatile flow results and, when coupled with the vessel-wall expansion, was used to calculate the instantaneous elastic modulus from a novel, time-resolved two-dimensional (i.e. axial and circumferential) stress model. The circumferential instantaneous elasticity obtained from the two-dimensional stress model was found to match the uniaxial tensile test for strains below 50%. The agreement in elasticity between the two stress states reveals that the two-dimensional stress model accurately resolves the circumferential stress of the viscoelastic aorta at physiological strains (8%-30%). At higher strains, results from pulsatile flow generated a more compliant response than the uniaxial measurements. Viscoelastic properties (storage modulus and loss factor) were also calculated using the two-dimensional stress model and compared to those obtained from uniaxial tests. While instantaneous elasticity matched between the cylindrical and uniaxial loading, the viscoelastic behaviour significantly diverged between stress states. The storage modulus obtained from the pulsatile flow data was dependent on mean Reynolds number, while the uniaxial storage modulus results exhibited a strong inverse dependency on the frequency. The loss factor for the pulsatile flow data increased alongside the frequency, while the uniaxial data indicated a constant loss factor over the entire frequency range. The results of the current study show that the two-dimensional stress model can accurately extract the material properties of the ex vivo porcine aorta.

Endoscopic radial artery harvesting for U-clip EC-IC bypass in the treatment of a giant petrous internal carotid artery aneurysm: technical case report.

INTRODUCTION: High-flow extracranial-intracranial (EC-IC) bypass and aneurysm trapping constitutes a well-known surgical solution for internal carotid artery (ICA) aneurysms that are not amenable to clip ligation or endovascular therapy. The advantages of the radial artery (RA) as a conduit for myocardial revascularization have become widely accepted, with a better patency rate than that of the saphenous vein. CASE REPORT: A 66-year-old woman was found to harbour a right giant, partially thrombosed aneurysm of the intrapetrous segment of the internal carotid artery. Endoscopic harvesting of the RA was achieved combining a resterilizable retractor and a vessel sealing system. After neck dissection, the main trunk of the middle cerebral artery (MCA), its branches, and part of the aneurysm were isolated through a right fronto-orbito-zygomatic craniotomy. The external carotid artery, distal to the origin of the facial artery, was chosen in the neck for an end-to-end microanastomosis. The temporal branch of the MCA was selected for an end-to-side microanastomosis with the radial graft using ten U-clips. The total temporary occlusion time was 13 min. The post-operative course was uneventful. CONCLUSION: Endoscopic technique provides improved patient satisfaction, especially in terms of length of the surgical incision, when compared to the conventional approach. Combined with the innovative use of U-clips, this case illustrates how new technologies can simplify ECA-ICA bypass surgery while yielding a better cosmetic and functional outcome.

Endoscopic radial artery harvesting for U-clip high-flow EC-IC bypass: technical report.

INTRODUCTION: Bypass and aneurysm trapping constitute a well-known surgical solution for aneurysms that are not suitable for clipping or coiling. New techniques are available that make EC-IC bypass procedures easier, safer and, possibly, less invasive. The nitinol self-closing U-Clip device (Medtronic, Inc., Minneapolis) has been designed to facilitate the interrupted suture technique by eliminating the need for suture management, knot tying, and surgical assistance. MATERIALS AND METHODS: We present two consecutive U-clip bypass procedures in which the radial artery graft was harvested endoscopically. RESULTS: This novel bypass technique employs endoscopy to minimise arm injury due to radial artery harvesting and self-closing U-clips to simplify the intracranial micro-anastomosis and reduce the temporary occlusion time. Angiography confirmed bypass patency in all patients. DISCUSSION: Combined with the innovative use of U-clips, these two examples illustrate how new technologies can simplify EC-IC bypass surgery while yielding a better cosmetic and functional outcome.

Prospective evaluation of a new sternal closure method with thermoreactive clips.

OBJECTIVES: The role of the sternal closure techniques on the incidence of sternal dehiscence and wound infection are well defined among a high number of other variables involved. In the various series, the incidence of wound complication in cardiac surgery varies from 2 to 8%. The aim of our study is to evaluate the role of thermal-dependent shape-memory Nitillium clips in reducing the incidence of sternal dehiscence following sternotomy. METHODS: We perspectively randomized 1000 consecutive patients requiring cardiac surgery to evaluate the incidence of sternal wound complications (SWC), sternal dehiscence and/or other related complications. We compared Group I (500 patients), in which sternal closure was achieved with standard sternal wires, with Group II (500 patients), in which sternal approximation was carried out by means of thermoreactive Nitillium clips. The two randomized groups were comparable in terms of age, gender, Euroscore and risk factors for sternal/wound complications. RESULTS: In our study the overall incidence of SWC was 4.7%. The incidence of SWC was considerably higher in Group I (6.8%) when compared to Group II (2.6%) (P=0.003). Mechanical sternal dehiscence without infection occurred in 14 patients in Group I and in one patient in Group II (P=0.002). Despite sternotomy wound infection occurred similarly in both groups (15 patients in Group I vs. 12 patients in Group II), sternal revision was performed only in patients of Group I (Group I: 9/15 vs. Group II: 0/12; P=0.001). CONCLUSION: Thermal shape-memory Nitillium clips provided superior results in sternal osteosynthesis following midline sternotomy, due to a considerable reduction of sternal dehiscence and related complications. The clinical benefit of Nitillium clips was demonstrated even in patients with several risk factors for SWC.