| Bicuspid aortic valve(BAV)is the most common congenital heart abnormality,with a prevalence of approximately 0.5-2%in the general population,as suggested by various studies.Due to the biological and hemodynamic abnormalities,valve dysfunction or aortic abnormality often occur in the natural history of BAV,and eventually lead to severe complications and increased burden on individuals and society in terms of healthcare when left untreated.Valve replacement remains the mainstream treatment recommended by guidelines for BAV valve dysfunction.However,different types of prosthetic valves have significant drawbacks.Biological prosthetic valves may result in limited durability and susceptibility to degeneration,while mechanical prosthetic valves demand lifelong anticoagulation which increases the risk of thromboembolic events.Recently,bicuspid aortic valve repair has emerged as a novel therapeutic approach,offering an alternative to valve replacement surgery.Current guidelines recommend BAV repair for young patients with active valves,minimal degeneration or thickening,and limited calcification.Several studies have demonstrated favorable perioperative outcomes and satisfactory medium to long-term survival rates associated with BAV repair.It is noteworthy that BAV repair encompasses not only valve repair but also comprehensive restoration of the aortic annulus,ascending aorta,and aortic root.Dilation of the aortic annulus is considered an independent risk factor for disease progression and surgical durability.Therefore,annuloplasty and the selection of appropriate annuloplasty techniques assume significant importance.Nevertheless,there is ongoing debate regarding the threshold for annuloplasty and the necessity of performing the procedure.Moreover,robust evidence directly comparing the effectiveness of different annuloplasty techniques remains limited.BAV repair is a relatively new and intricate surgical technology that involves a variety of complex techniques.The number of patients who have undergone BAV repair remains limited,making it challenging to directly compare outcomes among a large and homogeneous population.Assessing surgical outcomes using traditional endpoints requires a significant number of patients and long-term follow-up,which can be challenging in clinical studies on BAV repair.Hemodynamics play a crucial role in the development and progression of cardiovascular diseases.They not only correlate closely with anatomical changes but also reflect functional changes to some extent in BAV dysfunction and aortic pathologies.Additionally,hemodynamic analysis provides realtime results,allowing for immediate evaluation of surgical outcomes.Recently,advancements in cardiac imaging techniques and computational fluid dynamics have sparked discussions on image-based,non-invasive hemodynamic assessment,offering technical support for perioperative hemodynamic evaluation in BAV repair.Based on the discussion above,the main research content is as follows:PART 1 Influence of Annuloplasty on Early-to-Mid-term Durability of Bicuspid Aortic Valve RepairObjective:It is important to consider how to manipulate the aortic annulus for patients undergoing bicuspid aortic valve repair.This study aims to analyze the impact of annuloplasty on patients undergoing BAV repair,and assess the differences in outcomes of different techniques of annuloplasty.Methods:Consecutive patients who underwent BAV repair at Fuwai Hospital were included in this study between April 24,2017 and June 1,2022.The patients were divided into two groups based on whether aortic annuloplasty was performed.Diameter of aortic annulus measured intraoperatively was used for single-variable matching,in which the annuloplasty group was set as the control group and the non-annuloplasty group was set as the treated group.A matching ratio of 1:4 was set to correct the difference in annulus diameter between the two groups.In addition,patients undergoing annuloplasty were divided into suture annuloplasty group,external ring annuloplasty group,and David I group,and event-free survival were analyzed among different groups.The primary outcome of interest was the occurrence of grade 3 or higher aortic valve regurgitation after surgery.Kaplan-Meier curve was used for survival analysis,and Cox proportional hazards model was used for risk factor analysis.Results:A total of 106 patients were included for analysis.17 patients did not undergo annuloplasty,while 89 patients did.The overall occurrence rate of moderate or severe aortic regurgitation(AR)at 30 days was 0.9%,and the 3-year survival rate free from AR≥3 was 93.1%(95%CI 87.9-98.7%).The 3-year survival rate free from AR≥3 was 78.2%(95%CI 59.2-97.2%)in the group without annuloplasty compared with a 3-year survival rate free of 96.5%(95%CI 91.8-100%)in the group with annuloplasty,which demonstrated a significant difference in survival(P=0.002).Analysis after matching for annulus diameters revealed no statistical difference between the two groups(P=0.068),but the annuloplasty group showed a better survival trend.There was no statistically significant difference in survival among the 3 groups of different annuloplasty techniques(P=0.235).Multivariable regression analysis revealed that age(HR 0.88,95%CI 0.80.97,P=0.007)and application of annuloplasty(HR 0.01,95%CI 0.00-0.11,P=0.001)were independent predictors for moderate or severe aortic valve regurgitation.Conclusions:Bicuspid aortic valve(BAV)repair demonstrates favorable early-to-mid-term outcomes.Annuloplasty reduces the risk of post-operative moderate or severe aortic valve regurgitation in the early-to-mid-term period and serves as a protective factor against the occurrence of moderate or severe regurgitation.PART 2 CT-Based Hemodynamic Analysis of Bicuspid Aortic Valve RepairObjective:This study is an exploratory study,which aims to explore the hemodynamic parameters suitable for CT by constructing a hemodynamic analysis model as well as describe the hemodynamic changes in patients undergoing bicuspid aortic valve repair before and after surgery.Methods:CT angiography(CTA)data of 1 patient undergoing BAV repair was used to construct a geometric model of the patient’s valve and aorta using medical imaging and computational fluid dynamics software such as Mimics/3Matic/Freeform.Finite element analysis and fluid calculation was performed using the SIMULIA software series to construct a mesh model,and LBM was set for calculation of FSI.Finally,the Ansys software series were used for solving and post-processing to obtain multiple hemodynamic parameters,including flow velocity,vorticity,helicity,flow displacement index,and stress parameters such as wall shear stress.Results:The study found that the hemodynamic parameters can be analyzed by constructing a CT-based hemodynamic model.After BAV repair,the maximum blood flow velocity of the patient decreased from 2.316m/s to 2.012m/s,and the degree of blood flow displacement at the valve orifice decreased.The helicity of the blood flow in the aorta decreased from level 3 to level 1,and the preoperative blood flow was more in line with the right-hand rule compared to the postoperative blood flow.The intensity of the nearwall vortex after surgery significantly decreased,and the velocity of the vortex decreased.The fluid displacement index decreased from 3.6mm to 2.8mm,and the degree of displacement decreased from 21.18%to 16.47%.The preoperative high WSS distribution was more extensive,and the position of the maximum wall shear stress changed after surgery,but the maximum WSS after surgery(88.80Pa)was higher than before(64.88Pa).Conclusion:The combination of computational fluid dynamics and fluid-structure interaction makes it feasible to construct a hemodynamic analysis model and explore hemodynamic parameters based on cardiac CTA.This method can be used to evaluate hemodynamics before and after BAV repair surgery.However,further verification with more cases is still needed. |
