Re-creation of a sinuslike graft expansion in Bentall procedure reduces stress at the coronary button anastomoses: A finite element study.

OBJECTIVE

The Bentall procedure is routinely performed using a straight Dacron graft coupled with a mechanical or a biologic valve. Creation of coronary ostia buttons significantly reduces tension on the coronary anastomoses and consequently the incidence of pseudoaneurysm formation. We sought to evaluate if the use of a specifically designed graft with a sinuslike root portion that bulges out upon pressurization can reduce stress on coronary anastomoses. A finite element computer-assisted stress analysis was used to simulate these 2 different anatomic conditions and to analyze tension in computed tomographic scans obtained from patients operated on with either a straight or a "sinus" graft.

METHODS

Theoretical models of the procedures with finite element computer-aided design technique were created and tested with the Abaqus Standard Suite, verifying the pattern of stress and strain when a uniform pressure of 200 mm Hg was applied to the model. Next, using SimpleWare SCanIP technology, computed tomographic scans of patients having both procedures were used to obtain finite element mesh models. A uniform pressure of 200 mm Hg was then applied, and the distribution of stress and strain was analyzed.

RESULTS

Von Mises Charts are color-coded, computational, 3-dimensional stress-pattern graphics that show that stress around the coronary ostia in a standard straight graft model is nearly double compared with the model with sinuses (peak stress of 0.4 Mpa for the sinus model and 0.7 Mpa for the traditional straight model). In computed tomographic scan reconstructions, the stress contour is uniformly distributed in the graft with sinuses, and it is highly concentrated around the ostia in the straight graft. Accordingly, higher-peak stress values are registered in the straight configuration (1.8 MPa for the sinus graft and 2.5 MPa for standard graft).

CONCLUSION

Even though finite elements technique is necessarily a simplification of a real biologic environment, all tests seem to indicate that a standard tubular graft gives a higher stress to coronary sutures. Relieving the stress on the coronary anastomoses by using a graft with preformed sinuses of Valsalva may decrease the incidence of postoperative complications such as bleeding and late pseudoaneurysm formation.