P. Knez

Strain Measurement of Abdominal Aortic Aneurysm with Real-time 3D Ultrasound Speckle Tracking

OBJECTIVES Abdominal aortic aneurysm rupture is caused by mechanical vascular tissue failure. Although mechanical properties within the aneurysm vary, currently available ultrasound methods assess only one cross-sectional segment of the aorta. This study aims to establish real-time 3-dimensional (3D) speckle tracking ultrasound to explore local displacement and strain parameters of the whole abdominal aortic aneurysm. MATERIALS AND METHODS Validation was performed on a silicone aneurysm model, perfused in a pulsatile artificial circulatory system. Wall motion of the silicone model was measured simultaneously with a commercial real-time 3D speckle tracking ultrasound system and either with laser-scan micrometry or with video photogrammetry. After validation, 3D ultrasound data were collected from abdominal aortic aneurysms of five patients and displacement and strain parameters were analysed. RESULTS Displacement parameters measured in vitro by 3D ultrasound and laser scan micrometer or video analysis were significantly correlated at pulse pressures between 40 and 80 mmHg. Strong local differences in displacement and strain were identified within the aortic aneurysms of patients. CONCLUSION Local wall strain of the whole abdominal aortic aneurysm can be analysed in vivo with real-time 3D ultrasound speckle tracking imaging, offering the prospect of individual non-invasive rupture risk analysis of abdominal aortic aneurysms.

Does vascular stapling improve compliance of vascular anastomoses

Elastic properties of vessel walls are altered by vascular anastomoses. Such alterations may lead to neointimal hyperplasia, which is a common cause of reocclusion following vascular surgery. The severity of paraanastomotic hypercompliant zones and anastomotic compliance drop depend on suturing material and on elastic properties of the anastomotic vessel segments. This study compares paraanastomotic hypercompliance and anastomotic compliance drop when using a new vascular closure system (VCS®) and a conventional, continuous suture line in the preparation of end-to-end anastomoses. Compliance of artery-artery, vein-artery, and polytetrafluoroethylene-artery anastomoses was measured in an artificial circulation system at mean pressures of 60, 90, and 120 mm Hg, comparing conventional suturing and the VCS. When using the VCS for vein-artery anastomoses, significantly less postanastomotic hypercompliance was achieved at mean pressures of 60 mm Hg (14.2 ±3.8% above remote postanastomotic area), compared to suture (55.1 ±14.8%, p < 0.05). At 90 mm Hg, respective values were 1 1.0 ±2.3% for VCS and 54.7 ±10.1% for suture, p<0.01. At 120 mm Hg, in polytetrafluoroethylene-artery anastomoses, the anastomotic compliance drop was significantly less when using the continuous suture line (93.9 ±1.1% below remote postanastomotic compliance), compared to VCS (97.2 ±0.2%, p< 0.05). Compared to conventional suturing, use of the VCS reduced postanastomotic hypercompliance in vein-artery anastomoses.

Altered in-stent hemodynamics may cause erroneous upgrading of moderate carotid artery restenosis when evaluated by duplex ultrasound

OBJECTIVE To assess the influence of stent application on in-stent hemodynamics under standardized conditions. METHODS Ovine common carotid arteries before and after stent (6 × 40 mm, sinus-Carotid-RXt, combined open-closed cell design; Optimed, Ettlingen, Germany) application were used. Plastic tubes, 10 mm in length, simulating stenosis were placed in the middle of the applied stent to induce different degrees of stenosis (moderate 57.8% and severe 76.4%). Flow velocity and dynamic compliance were, respectively, measured with ultrasound and laser scan; proximal, in-stent, and distal to the stented arterial segment (1 cm proximal and distal) in a pulsatile ex vivo circulation system. RESULTS Stent insertion caused the in-stent peak systolic velocity to increase 22% without stenosis, 31% with moderate stenosis, and 23% with severe stenosis. Stent insertion without stenosis caused no significant increase in in-stent end-diastolic velocity (EDV) but a 17% increase with moderate stenosis. In severe stenosis, EDV was increased 56% proximal to the stenosis. Compliance was reduced threefold in the middle of the stented arterial segment where flow velocity was significantly increased. CONCLUSIONS With or without stenosis, stent introduction caused the in-stent peak systolic velocity to become significantly elevated compared with a nonstented area. EDV was also increased by stent insertion in the case of moderate stenosis. The stent-induced compliance reduction may be causal for the increase in flow velocity since the stent-induced flow velocity elevation appeared in the stented area with low compliance. Because of altered hemodynamics caused by stent introduction when measured by duplex ultrasound, caution is prudent in concluding that carotid artery stenting is associated with a higher restenosis rate than carotid endarterectomy. Mistakenly upgrading moderate to severe restenosis could result in unnecessary reintervention. CLINICAL RELEVANCE Clinical experience and prior studies support the supposition that restenosis after carotid artery stenting in carotid lesions displays erroneously elevated velocity when evaluated by duplex ultrasound (DUS), thus contributing to misleading interpretation of the degree of stenosis. This study, in contrast to studies of other groups, employs exactly the same conditions to measure flow with DUS in an unstented and then stented section of the carotid artery. Since DUS is the first-choice tool for carotid artery evaluation, knowledge about inexactness of the method is essential to avoid errors in treatment or follow-up decisions.

STRAIN MEASUREMENT OF ABDOMINAL AORTIC ANEURYSM WITH 3D ULTRASOUND SPECKLE TRACKING

The main risk associated with abdominal aortic aneurysm is rupture caused by mechanical failure of the vascular tissue. To predict individual rupture risk it is necessary to determine biomechanical properties of the aneurysm in vivo, which until the present, has been limited to 2-dimensional analysis of the aorta using conventional sonography, CT or MRI [Vorp, 2005]. Recently, 3-dimensional timeresolved speckle tracking ultrasound has been introduced to measure biomechanical strain parameters of the heart in vivo [Kapetanakis, 2005]. The aim of this investigation was to establish and validate this 3D ultrasound method, applied to the abdominal aortic aneurysm.

Einfluss eines External Dacron Mesh Support auf die Paraanastomotische Hypercompliance (PHZ) von Gefäßanastomosen — ex vivo Studie

Paraanastomotische Hypercompliance Zonen sind ein bekanntes Phanomen vascularer Anastomosen. Sie werden als mitverantwortlich fur die Entstehung der subintimalen Hyperplasie angesehen. Der Einfluss dieser veranderten biomechanischen Eigenschaften auf die Entstehung spater Gefasstenosen und- verschlusse ist Gegenstand intensiver Grundlagenforschung.

Endotension und Compliance der Aneurysmawand — eine in vitro Untersuchung

Objectives Endovascular aneurysm repair (EVAR) creates a closed chamber except for the presence of any patent branches, but the intra-sac pressure is never zero. The present study was designed to investigate whether, and to what extent, pressure is influenced by the aneurysm wall compliance.

Auch minimale Typ I Endoleaks nach Stentgrafttherapie des Bauchaortenaneurysmas führen zu einer Angleichung des Drucks im Aneurysmasack an den Systemdruck — eine in-vitro Studie

Background Although endovascular treatment of abdominal aortic aneurysms with a stent graft has been employed since 1990, safety is still controversial since type 1 endoleaks lead to reperfusion of the aneurysmal sac. The effect of small endoleaks on pressure in the aneurysmal sac with subsequent rupture risk has not been fully investigated. This study examines average pressure and pressure amplitude in the aneurysmal sac of abdominal aortic aneurysm models with a stent graft, depending on the diameter of a type 1 endoleak.

Laparoskopische Resektion eines Aneurysmas der Vena cava inferior unter Verwendung eines Telemanipulators

Im Vergleich zum offenen Vorgehen ist in der laparoskopischen Chirurgie die Moglichkeit der Instrumentenfuhrung signifikant eingeschrankt. Durch Einsatz von Robotic-Systemen lassen sich Instrumente mit allen Freiheitsgraden verwenden. Durch zusatzliche Filterung der Bewegungsubertragung vom Chirurgen auf die Instrumente ist so ein erheblicher Prazisionsgewinn gegeben. Die Effektivitat solcher Telemanipulatoren in der laparoskopischen Chirurgie ist mittlerweile auch fur die klinische Praxis belegt. Wir berichten hier uber die - nach unserer Kenntnis — erste laparoskopische Operation an der Vena cava inferior (V. cava inf.) unter Verwendung eines solchen Telemanipulators. Patient und Methode: Zugewiesen wurde uns eine 21jahrige Frau mit einem rechtsseitigen retroperitonealen Tumor, der zu einer kompletten Thrombose der V. cava inf. und zur ventralen Verlagerung des rechten Ureters gefuhrt hatte. Trotz mehrfacher Punktionsversuche war im Vorfeld keine eindeutige Histologiegewinnung moglich. Es wurde ein retroperitonealer Weichteiltumor ausgehend von glatten Muskelzellen der V. cava inf. vermutet.