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J Thorac Cardiovasc Surg 2004;128:117-123
© 2004 The American Association for Thoracic Surgery

Evolving technology

Flow dynamics of the St Jude Medical Symmetry aortic connector vein graft anastomosis do not contribute to the risk of acute thrombosis

^a Department of Bioengineering, Politecnico di Milano, Milan, Italy,
^b Cardiothoracic Unit, IRCCS San Raffaele, Milan, Italy

Received for publication December 20, 2003; revisions received February 18, 2004; revisions received February 26, 2004; accepted for publication March 18, 2004.

^* Address for reprints: Alberto Redaelli, MD, Department of Bioengineering, Politecnico di Milano, P.za L. da Vinci, 32, 20133 Milano, Italy
alberto.redaelli{at}polimi.it

BACKGROUND: The efficacy of the St Jude Medical Symmetry aortic connector (St Jude Medical, Inc, St Paul, Minn) for coronary artery bypass is currently debated. Potential drawbacks are the biocompatibility of the endoluminal device, the need for graft manipulation during the procedure, and the 90° offset of the vein graft from the ascending aorta, which may induce graft kinking and abnormal fluid dynamics. In this article, a computational approach was designed to investigate the fluid dynamics pattern at the proximal graft.

METHODS: Four models of hand-sewn anastomoses and two models of automated anastomoses were constructed; a finite volume technique was used to simulate realistic graft fluid dynamics, including aortic compliance and proper aortic and graft flow rates. The anastomosis geometry performance was analyzed by calculating time-averaged wall shear stress and the oscillating shear index at the toe and heel regions of the proximal graft.

RESULTS: Time-averaged wall shear stress was significantly lower in the hand-sewn anastomosis models than in the two models that simulated the use of the aortic connector (0.38 ± 0.07 Pa vs 1.32 ± 0.4 Pa). Higher oscillating shear index values were calculated in the hand-sewn anastomosis models (0.15 ± 0.02 Pa vs 0.06 ± 0.02 Pa).

CONCLUSIONS: Automated anastomosis geometry is associated with less critical fluid dynamics than with conventional hand-sewn anastomosis: the shape of the proximal graft induces more physiological wall shear stresses and less oscillating flow, suggesting a lower risk of atherosclerotic plaque and intimal hyperplasia as compared with conventional anastomosis geometry. Therefore, the reported early thrombosis and late failure of the St Jude Medical aortic connector anastomoses are not related to unfavorable fluid dynamics.

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