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Fluid dynamics simulation of right ventricular outflow tract oversizing
Denis Berdajs1, Selim Mosbahi2, Jan Vos3
1Department of Surgery and Anesthesiology, Cardiovascular Research, University Hospital Lausanne, Lausanne, Switzerland denis.berdajs@bluewin.ch.
Insights
Oversizing right ventricular outflow tract (RVOT) conduits by 4 mm may improve graft durability. This study used CFD to analyze hemodynamic factors in oversized RVOT models, finding optimal conditions similar to native RVOT.
Area of Science:
- Cardiovascular Surgery
- Biomedical Engineering
- Fluid Dynamics
Background:
- Right ventricular outflow tract (RVOT) repair in children has a high reoperation rate.
- Intimal hyperplasia and arteriosclerosis limit graft durability.
- Local shear stress and pressure influence intimal hyperplasia.
Purpose of the Study:
- To investigate hemodynamic factors in oversized RVOT models using CFD.
- To identify the optimal degree of oversizing for a 12-mm native RVOT.
- To reduce reoperation rates in pediatric cardiac surgery.
Main Methods:
- Implanted valve conduits of varying sizes (12, 16, 18, 20 mm) in 20 pigs.
- Measured pressure and flow at different rates in RVOT and pulmonary arteries.
- Performed 3D CFD simulations to analyze local shear stress and pressure.
Main Results:
- Low shear stress (0-2 Pa) and high-pressure areas (11.5-12.1 mmHg) were observed at distal anastomoses and pulmonary artery ostia.
- These conditions occurred across all tested flow rates and oversized geometries.
- The 16-mm model showed hemodynamic profiles similar to the native 12-mm RVOT.
Conclusions:
- Oversizing a 12-mm native RVOT by no more than 4 mm is suggested.
- Hemodynamic conditions in the 16-mm oversized model mimic the native RVOT.
- This approach may mitigate intimal hyperplasia and improve graft durability.
Objectives:
Repair of the right ventricular outflow tract (RVOT) in paediatric cardiac surgery remains challenging due to the high reoperation rate. Intimal hyperplasia and consequent arteriosclerosis is one of the most important limitation factors for graft durability. Since local shear stress and pressure are predictive elements for intimal hyperplasia and wall degeneration, we sought to determine in an oversized 12-mm RVOT model, with computed fluid dynamics simulation, the local haemodynamical factors that may explain intimal hyperplasia. This was done with the aim of identifying the optimal degree of oversizing for a 12-mm native RVOT.
Methods:
Twenty domestic pigs, with a weight of 24.6 ± 0.89 kg and a native RVOT diameter of 12 ± 1.7 mm, had valve conduits of 12, 16, 18 and 20 mm implanted. Pressure and flow were measured at 75, 100 and 125% of normal flow at RVOT at the pulmonary artery, pulmonary artery bifurcation and at the left and right pulmonary arteries. Three-dimensional computed fluid dynamics (CFD) simulation in all four geometries in all flow modalities was performed. Local shear stress and pressure conditions were investigated.
Results:
Corresponding to 75, 100 and 125% of steady-state flow, three inlet velocity profiles were obtained, 0.2, 0.29 and 0.36 m/s, respectively. At inflow velocity profiles, low shear stress areas, ranged from 0 to 2 Pa, combined with high-pressure areas ranging from 11.5 to 12.1 mmHg that were found at distal anastomosis, at bifurcation and at the ostia of the left and right pulmonary arteries in all geometries.
Conclusions:
In all three oversized geometries, the local reparation of shear stress and pressure in the 16-mm model showed a similar local profile as in the native 12 mm RVOT. According to these findings, we suggest oversizing the natural 12-mm RVOT by not more than 4 mm. The elements responsible for wall degeneration and intimal hyperplasia remain very similar to the conditions present in native RVOT.
