BackgroundRoutine vascular surgery operations involve stitching of disconnected human arteries with themselves or with artificial grafts (arterial anastomosis). This study aims to extend current knowledge and provide better-substantiated understanding of the mechanics of end-to-end anastomosis through the development of an analytical model governing the dynamic behavior of the anastomotic region of two initially separated arteries.MethodsThe formulation accounts for the arterial axial-circumferential deformation coupling and suture-artery interaction. The proposed model captures the effects of the most important parameters, including the geometric and mechanical properties of artery and sutures, number of sutures, loading characteristics, longitudinal residual stresses, and suture pre-tensioning.ResultsClosed-form expressions are derived for the system response in terms of arterial radial displacement, anastomotic gap, suture tensile force, and embedding stress due to suture-artery contact interaction. Explicit objective functionalities are established to prevent failure at the anastomotic interface.ConclusionsThe mathematical formulation reveals useful interrelations among the problem parameters, thus making the proposed model a valuable tool for the optimal selection of materials and improved functionality of the sutures. By virtue of their generality and directness of application, the findings of this study can ultimately form the basis for the development of vascular anastomosis guidelines pertaining to the prevention of post-surgery implications.

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Background:When subjected to time-dependent blood pressure, human arteries undergo large deformations, exhibiting mainly nonlinear hyperelastic type of response. The mechanical response of arteries depends on the health of tissues that comprise the artery walls. Typically, healthy arteries exhibit convex strain hardening under tensile loads, atherosclerotic parts exhibit stiffer response, and aneurysmatic parts exhibit softening response. In reality, arterial dynamics is the dynamics of a propagating pulse, originating in heart ventricle, propagating along aorta, bifurcating, etc. Artery as a whole cannot be simulated as a lump ring, however its cross section can be simulated as a vibrating ring having a phase lag with respect to the other sections, creating a running pressure wave. A full mathematical model would require fluid-solid interaction modeling continuity of blood flow in a compliant vessel and a momentum equation. On the other hand, laboratory testing often uses small-length arteries, the response of which is covered by the present work. In this way, material properties that change along the artery length can be investigated.Objective:The effect of strain hardening on the local dynamic response of human arteries (excluding the full fluid-structure interaction) is examined through appropriate hyperelastic models related to the health condition of the blood vessel. Furthermore, this work aims at constituting a basis for further investigation of the dynamic response of arteries accounting for viscosity.Method:The governing equation of motion is formulated for three different hyperelastic material behaviors, based on the constitutive law proposed by Skalak et al., Hariton, and Mooney-Rivlin, associated with the hardening behavior of healthy, atherosclerotic, and aneurysmatic arteries, respectively. The differences between these modelling implementations are caused by physiology, since aneurysmatic arteries are softer and often sclerotic arteries are stiffer than healthy arteries. The response is investigated by proper normalization of the involved material parameters of the arterial walls, geometry of the arteries, load histories, time effects, and pre-stressing. The effect of each problem parameter on the arterial response has been studied. The peak response of the artery segment is calculated in terms of radial displacements, principal elongations, principal stresses, and strain-energy density. The validity of the proposed analytical models is demonstrated through comparison with previous studies that investigate the dynamic response of arterial models.Results:Important metrics that can be useful to vascular surgery are the radial deformation and the maximum strain-energy density along with the radial resonance frequencies. These metrics are found to be influenced heavily by the nonlinear strain-hardening characteristics of the model and the longitudinal pre-stressing.Conclusion:The proposed formulation permits a systematic and generalizable investigation, which, together with the low computational cost ...

End-to-side vascular anastomosis has a considerable complexity regarding the suturing of the juncture line between the artery and the graft. The present study proposes a stress-concentration methodology for the prediction of the stress distribution at the juncture line, aiming to provide generic expressions describing the response of an end-to-side anastomosis. The proposed methodology is based on general results obtained from the analysis of pipe connections, a topic that has been investigated in recent years in the field of offshore structural engineering. A key aspect for implementing the stress-concentration-factor approach is the recognition that the axial load due to pressure and flow dynamics exerted along the graft axis controls the "hot spots" on the juncture line, which in turn affects the mechanical response of the sutures. Several parameters, identified to influence the suture line response, are introduced in closed-form expressions for the suture line response calculations. The obtained results compare favorably with finite element results published in the literature. The proposed model predicts analytically the suture line response of end-to-side anastomosis, while capturing the influence of and interdependence among the problem parameters. Lower values of the graft radius, the distance between sequential stitches, and the intersecting angle between the artery and the graft are some of the key parameters that reduce the suture line response. The findings of this study are broad in scope and potentially applicable to improving the end-to-side anastomosis technique through improved functionality of the sutures and optimal selection of materials and anastomosis angle.

Suture line stress concentration and intimal hyperplasia are related to the long-term complications of end-toside and side-to-side anastomosis. Several factors, such as hemodynamic effects, biological activities and the mechanical properties of the blood vessels, are identified to influence the problem. Yet, it is not completely clear which are the factors that influence most the long-term complications and in what specific way. This study aims to examine if elastic (compliance) mismatch increases the stress concentration and intimal thickening at the suture line. Better compliance may be obtained by using grafts with similar mechanical properties to the host artery or by anastomosis techniques that utilize vein patches and cuffs (Taylor-patch and Miller-cuff anastomosis). The anastomosis model used in this study is a circular cylindrical system consisting of two semi-cylinders, interconnected by two hinges. The internal blood pressure is applied on the arterial walls. The static and dynamic responses are analytically derived in terms of radial and tangential displacements, internal forces and strains of the two blood vessels and rotation of their cross-section. Results suggest that increased elastic mismatch between the artery and the graft may promote elevated intimal thickening due to large incompatible angles at the junction, whereas there is no correlation between elastic mismatch and elevated stress concentration at the suture line. Another interesting application of the present model is the patching of arteries as applied in carotid endarterectomy.