New trends in vascular surgery.

Since the beginning of the 21st century, changes in the western population as the possibility of using endovascular techniques have modified the indications and the operative techniques in all areas of vascular surgery. The classical bypass surgery, which required arterial substitutes, is now less and less used.So, the goal of the arterial research should not be centered on the search of the ideal substitute, but on improving minimally invasive techniques, as cell therapy and regenerative medicine. All these techniques will be the new treatments of the atherosclerosis disease in the near future.

[Introduction to vascular engineering]. / Introduction à l'ingénierie vasculaire.

Vascular engineering developed through advancing knowledge of the physiological and pathological processes operating in cells and tissues subjected to environmental mechanical stress. We review briefly the more relevant cellular and general mechanism characteristic of vascular tissue examining the performances obtained with prosthetic materials (allografts, synthetic grafts) and current research and development of new vessel substitutes (biohybrids or biovessels).

[Value of arteriography scanning in lower limb artery evaluation: a preliminary study]. / Intérêt de l'artério-scanner dans le bilan des artériopathies des membres inférieurs: étude préliminaire.

PURPOSE: The purpose of this study was to assess the feasability of CT Angiography (CTA) with a single row of detectors and to compare it to digital subtraction angiography (DSA) in the evaluation of lower limb peripheral arterial disease. MATERIAL: and methods. A total of 22 patients underwent 24 lower limb Helical CTA using a Somatom Plus 4A (Siemens) and 24 DSA using an Angiostar unit (Siemens). CT angiography was performed in one acquisition (collimation 3mm/ couch motion 9mm/ interval 2mm) with tube rotation time of 0.75 sec from the aortic bifurcation to the calf. DSA was performed after catheterization of a common femoral artery using the Seldinger technique. Arteries were classified in four categories (normal or stenosis<50%, stenosis>50%, occlusion, aneurysm). VRT images and axial source images were assessed by two independent radiologists whereas digital angiographies were read by a vascular radiologist. RESULTS: Global interobserver agreement was good (Kappa=0.71). The degree of agreement between CTA and DSA ranged from low to excellent (0.25 to 0.97) depending on the artery. CONCLUSION: Lower limb CT angiography is a promising non invasive technique. VRT allows quick evaluation. However, is not accurate enough to replace digital angiography.

Value of bone scintiscan for diagnosis of arterial prosthesis infection: preliminary results.

Diagnosis of arterial prosthetic infection is often difficult to confirm. Several cases of lower extremity hypertrophic osteoarthropathy (HOA) have been associated with arterial prosthetic infection. The presence of bone and joint abnormalities could constitute an early sign of HOA. The purpose of this prospective study was to determine the diagnostic value of routine bone scintiscan in patients hospitalized for suspected arterial prosthesis infection. Between December 1995 and May 1997, 17 patients with suspected infection were admitted to our institution. All underwent bone scintiscan before surgical treatment. Presence or absence of infection was defined according to the criteria proposed by Yeager. During the same period, bone scintiscan was performed in a control group of 8 patients with arterial prostheses but no clinical or laboratory signs of infection. Scintiscans were studied to detect bone and joint abnormalities distal to the arterial prosthesis. The results of this preliminary study indicate that routine bone scintiscan can assist definitive diagnosis in patients with suspected arterial prosthesis infection. Demonstration of bone and joint abnormalities distal to a prosthesis appears to be a fairly sensitive and highly specific sign of infection.

[Modeling of elastic deformation and vascular resistance of arterial and venous vasa vasorum]. / Modélisation de la déformation élastique et de la résistance à l'écoulement des vasa vasorum des artères et des veines.

As in most living tissues, a network of nutritional vessels, the so-called vasa vasorum, irrigates the vessel wall under physiological conditions. An alteration or obstruction of this network can induce severe lesions. Most normal arteries and veins are irrigated by a vasa vasorum network located mainly in the adventice. They essentially supply oxygen to the outer layers of the vascular wall, the inner layer being mainly oxygenated by direct diffusion from bloodstream. Vasa vasorum responds to vasomotor stimuli and can even regress, e.g., after vascularization of arterial grafts. Their pathophysiological importance for arteries is now established. Indeed, it is known that an infusion disorder or vasa vasorum alteration may induce or promote early atherosclerotic lesions, fibrodysplasia or even media necrosis. From a mechanical point of view, and considering the three layers as a unique material, the vessel shows non-isotropic linear elastic and incompressible (v = 0.5) behaviour in the case of minimal or moderate deformation. But in the case of major deformation, the vessel displays a non-linear behaviour. The interaction between vasa vasorum supply and the mechanical properties of the arterial vascular wall can promote the occurrence of aneurysms as soon as vasa vasorum irrigation decreases. Some authors have hypothesized that these microvessels could fulfil the same function in the venous wall. It appears also that microcirculation flow rates are lower in varicose veins than in healthy ones and that partial oxygen pressure, already low in a healthy vein media, is even lower in a varicose vein. All these facts underline the importance of supply by the vasa vasorum network and its determining role in maintaining vascular wall integrity. In addition, the influence of vessel non-linear properties and their pathological changes on microcirculation would partially explain media necrosis in arteries and veins. Studying vascular wall deformation under the influence of intraluminal pressure revealed that an initially circular vasa vasorum rapidly takes on an elliptical shape which results more from crosswise circumferential stretching of the wall than from radial crushing. This induces increased hydraulic resistance. Thus permanent overpressure reduces vascular wall irrigation. Once the wall has been devascularized, it will loose its elasticity, harden and retain its maximal deformation. A vicious circle is then created. This phenomenon, noticeable in arteries, could be more serious in veins because their walls are thinner and elasticity modulus is lower. For example, for an intraluminal overpressure of 100 mmHg in an artery and 10 mmHg in a vein the ellipticity of the vasa vasorum becomes 1.2 and 3 respectively. Based on the hypothesis of a linear elastic behaviour and a periodical intraluminal overpressure, the ratio of the two axis of an arterial vasa vasorum B/A varies from 1.13 to 1.28 for Pa = 100 + 30 sin (2 pi t) mmHg, and from 1.24 to 1.44 for Pa = 160 + 40 sin (2 pi t) mmHg. In this case, the ratio of hydraulic resistances R(ellipse)/R(circle) changes little (less than 1, the ratio of the axis varies from 1.1 to 2.6 for Pa = 5 + 5 sin (2 pi t) mmHg) and from 1.8 to 5.8 for Pa = 10 + 5 sin (2 pi t) mmHg). Thus the ratio of hydraulic resistance varies from 1 to 1.5 and from 1.2 to 2.8 respectively. In practice Young's modulus increases in parallel with luminal pressure by limiting vascular wall and vasa vasorum deformation. If we consider the non-linear behaviour of the vessel wall and suppose the same conditions of intraluminal pressure, the ratio of the axis of the venous vasa vasorum in a hypertensive patient varies from 1.6 to 2.6 (instead of 1.8 to 5.8 in the case of linear model). This ratio is higher than that of the healthy subject which is less than 1.7. So the vascular structure in physiological conditions itself reacts to the pressure increases which may jeopardize vasa vasorum irrigation by delaying mural transfor

Early rupture and degeneration of cryopreserved arterial allografts.

Arterial allografts are used in vascular surgery to solve a major problem: vascular reconstruction in the infected area. To palliate the unavailability and to reduce the risk of viral disease transmission, vascular allografts are currently cryopreserved and stored in tissue banks. In our recent clinical experience, we observed several cases of rupture and degeneration of cryopreserved arterial allografts. All indications are that current cryopreservation protocols are probably the cause for these degenerations.