Andrew Callington1, Quan Long2, Prashant Mohite3, Andre Simon3, Tarun Kumar Mittal3. 1. Brunel Institute for Bioengineering, Brunel University London, Uxbridge, United Kingdom. 2. Brunel Institute for Bioengineering, Brunel University London, Uxbridge, United Kingdom. Electronic address: quan.long@brunel.ac.uk. 3. Departments of Imaging and Surgery, Royal Brompton & Harefield National Health Service Foundation Trust, Harefield Hospital, Middlesex, United Kingdom.
Abstract
OBJECTIVES: To quantify the range of blood flow parameters in ascending aorta that can result from various angulations of outflow graft anastomosis of a left ventricular assist device (LVAD) to the aortic wall, as a means to understand the mechanism of aortic valve insufficiency. METHODS: A realistic aorta model with LVAD anastomosis was generated from computed tomographic images of a patient. Based on this model, the LVAD anastomosis geometry parameters, such as anastomosis locations, inclination angle, and azimuthal angle (cross-sectional plane) of the graft, were varied, to create 21 models. With the assumption of no flow passing the aortic valve, and a constant flow rate from the LVAD cannula, computational fluid dynamics simulations were used to study the blood flow patterns in the ascending aorta. In addition, pulsatile flows were assumed in the LVAD cannula, with the aortic valve opened during peak systole, for 2 specific anastomosis configurations, to evaluate the influence of the pulsatile flow profile and the transvalvular flow on the aortic flow patterns. RESULTS: Changes in the inclination angle, from 60° to 120°, or the azimuthal angle, from 90° to 120°, or moving from a lower to a higher anastomosis position, causes significant changes for all flow parameters. A lower anastomosis location, an inclination angle ≥90°, and an azimuthal angle of 60° or 120° are all capable of reducing blood flow stagnation in the aortic root and producing normal wall shear stress and moderate pressure values in the region. CONCLUSIONS: Carefully chosen anastomosis geometry is likely to be able to generate a close-to-normal hemodynamic environment in the aortic root. Greater knowledge of aortic valve remodeling may make possible the creation of favorable flow patterns in the aortic root, through optimization of surgical design to reduce or delay the occurrence of aortic valve insufficiency.
OBJECTIVES: To quantify the range of blood flow parameters in ascending aorta that can result from various angulations of outflow graft anastomosis of a left ventricular assist device (LVAD) to the aortic wall, as a means to understand the mechanism of aortic valve insufficiency. METHODS: A realistic aorta model with LVAD anastomosis was generated from computed tomographic images of a patient. Based on this model, the LVAD anastomosis geometry parameters, such as anastomosis locations, inclination angle, and azimuthal angle (cross-sectional plane) of the graft, were varied, to create 21 models. With the assumption of no flow passing the aortic valve, and a constant flow rate from the LVAD cannula, computational fluid dynamics simulations were used to study the blood flow patterns in the ascending aorta. In addition, pulsatile flows were assumed in the LVAD cannula, with the aortic valve opened during peak systole, for 2 specific anastomosis configurations, to evaluate the influence of the pulsatile flow profile and the transvalvular flow on the aortic flow patterns. RESULTS: Changes in the inclination angle, from 60° to 120°, or the azimuthal angle, from 90° to 120°, or moving from a lower to a higher anastomosis position, causes significant changes for all flow parameters. A lower anastomosis location, an inclination angle ≥90°, and an azimuthal angle of 60° or 120° are all capable of reducing blood flow stagnation in the aortic root and producing normal wall shear stress and moderate pressure values in the region. CONCLUSIONS: Carefully chosen anastomosis geometry is likely to be able to generate a close-to-normal hemodynamic environment in the aortic root. Greater knowledge of aortic valve remodeling may make possible the creation of favorable flow patterns in the aortic root, through optimization of surgical design to reduce or delay the occurrence of aortic valve insufficiency.