Hemodynamic Characteristics Of Inferior Vena Cava In Buddchiari Syndrome And Evaluation Of Hepatic Vein Recanalization

Part I.Evaluation of blood flow parameters and stenosis types of inferior vena cava in Budd-Chiari syndrome based on PC-MRIObjective To study the characteristics of blood flow parameters of inferior vena cava(IVC)in BCS,and to explore the value of PC-MRI in preoperative diagnosis of IVC stenosis or occlusion,so as to provide reference for preoperative evaluation of interventional therapy.Methods Patients with Budd-Chiari syndrome and healthy people were selected by clinical and ultrasonic examinations.Quantitative analysis: PC-MRI was performed at the distal end of inferior vena cava.The forward flow volume(FFV),backward flow volume(BFV),mean velocity(MV)and peak velocity(PV)were measured during the cardiac cycle.The differences of quantitative parameters between the two groups were compared by independent sample t-test.Qualitative analysis: Sagittal and corona l inferior vena cava dynamic pseudo color map were performed.A k appa test was used to compare the consistency of PC-MRI with MRV and DSA in the diagnosis of stenosis or occlusion of inferior vena cava.Results 64 patients with BCS and 12 controls were included in this study.The intraclass correlation coefficient(ICC)showed that the quantitative parameters of IVC measured by the two doctors in the control group and BCS group were highly consistent.The ICC values of FFV,BFV,MV and PV in the control group were 0.914,0.908,0.937 and 0.965,respectively;the ICC values of FFV,BFV,MV and PV in the BCS group were 0.883,0.899,0.935 and 0.942,respectively.The values of FFV,MV and PV of inferior vena cava in BCS group were significantly lower than those in control group(t = 13.56,16.47,12.38;P < 0.001),but there was no significant difference in BFV between the two groups(t = 0.515,P = 0.620).There was no significant difference in FFV(t = 1.609,P = 0.127)and BFV(t = 1.025,P = 0.324)between the two groups.MV(t = 2.883,P = 0.016)and PV(t = 2.599,P = 0.027)in the occlusion group were significantly lower than those in the non-occlusion group.The concordance of the two assessors with MRV and PC-MRI in detecting inferior vena cava occlusion was very good(k appa = 0.935 and k appa = 0.968).The consistency between MRV and DSA was good(k appa = 0.716),and PC and DSA was very good(k appa = 0.904).The sensitivity,specificity,PPV and NPV of MRV were 88.9%,83.8%,80.0% and 91.2% respectively.The sensitivity,specificity,PPV and NPV of PC-MRI were 96.3%,94.6%,92.9% and 97.2% respectively.Conclusion 1.PC-MRI has good repeatability in quantitative measurement and analysis of blood flow parameters of inferior vena cava in normal people and BuddChiari syndrome patients.2.The blood flow parameters of inferior vena cava in BuddChiari syndrome are significantly different from those in normal people,which can be used as an effective method to distinguish the occlusion and non-occlusion of inferior vena cava before interventiona l therapy.3.The diagnostic efficiency of PC-MRI qualitative method in the diagnosis of inferior vena cava occlusion is higher than that of conventional MRV,and has higher consistency compared with DSA.Part II.Establishment and analysis of Budd-Chiari syndrome model based on computational fluid dynamics Objective To establish the fluid models of normal subject and patient with BuddChiari syndrome before and after interventional treatment by using computational fluid dynamics method and compare the characteristics and differences of fluid parameters in these two groups.To evaluate the difference between computational fluid dynamic s and phase contrast MRI in the measurement of inferior vena cava velocity,and to provide a new and reliable evaluation method for the evaluation of Budd-Chia ri syndrome.Methods One patient with inferior vena cava obstructed BCS and one healthy person were randomly selected.The DICOM format images of inferior vena cava obtained by MRV were imported into Simpleware software,and the contour of inferior vena cava was extracted by threshold technology.Using the unstructured hexahedra l mesh generation technology of Scan FE module,the 3D model was transformed into a 3D finite element model in mesh file format,and the parameters of fluid inlet and outle t were set respectively.Based on CFD model,venous blood flow velocity,wall pressure and wall shear force were measured at different positions of inferior vena cava.The time distribution curves of inferior vena cava fluid velocity,wall pressure and wall shear force in normal subject and BCS patient before and after operation were drawn,and the characteristics of the parameters before and after BCS operation were compared.Phase contrast MR was used to measure the velocity of inferior vena cava at the same position,and the results were compared with those measured by CFD.Results In normal subject,the velocity and wall pressure of the IVC were evenly distributed,and the shear stress increased slightly in the posterior segment of the IVC.In BCS patient,the velocity of stenosis area of vena cava increased significantly,and the wall pressure of distal area of vena cava increased significantly,and the wall shear stress of stenosis area was the highest.After BCS interventiona l therapy,the blood flow velocity in the original stenosis area of inferior vena cava was significantly decreased,and the blood flow in the proximal and distal area of inferior vena cava fluctuate d significantly compared with that before operation.After the operation,the wall pressure of the proximal and the stenosis area increased,the wall pressure in the narrow area changed from negative pressure to positive pressure,while the wall pressure at the far end decreased significantly compared with that before operation.The wall shear stress decreased in all regions after operation,especially in the narrow area.Linear regression analysis showed that CFD and PC methods had good consistency in the flow measurement of each group,R2 values were 0.9351,0.9287 and 0.9180,respectively.The fitting degree of linear regression equation of normal people was slightly highe r than that of BCS patient.The mean,maximum and minimum values of NRMSE were 11.78%(7.8%-21.5%),14.10%(8.9%-16.8%)and 12.78%(4.9%-19.6%)before and after BCS operation.The difference of NRMSE value between normal people and preoperative patient was statistically significant(P = 0.024).Conclusion 1.CFD technology can effectively simulate the fluid model of the inferior vena cava,and quantitatively analyze the flow velocity,wall pressure and shear force before and after interventiona l treatment of BCS,which provides a new technica l method for evaluating the curative effect of BCS.2.Interventional therapy can reduce the blood flow rate in the stenosis area of inferior vena cava,reduce the wall shear force,and relieve the wall pressure of the distal end of inferior vena cava,which provides a theoretical basis for the follow-up study of restenosis based on hemodynamics.3.CFD and PC-MRI have good stability in the measurement of IVC flow velocity,which can be used as an important supplement to the measurement of IVC flow velocity.Part III.Application value of hepatic vein recanalization in hepatic vein type Budd-Chiari syndrome and its long-term follow-upObjective To compare the success rate and clinical success rate of interventiona l therapy between accessory hepatic vein(AHV)and main hepatic vein(MHV)in the treatment of hepatic vein type BCS,and to determine the influencing factors of postoperative restenosis and the cumulative patency rate and survival rate after the primary and secondary recanalization.Methods From July 2014 to December 2019,26 and 73 patients with hepatic venous type BCS treated with AHV and MHV recanalization treatment respectively were enrolled in this study.The operation success rate and clinical success rate of the two methods were evaluated.Successful operation was defined as target vein recanalization,normal blood flow and no obvious collateral vessels.Clinical success was defined as recovery of liver function and relief of symptoms after recanalization.Univariate and multivariate Cox regression models were used to identify the independent risk factors of restenosis.All patients were evaluated by clinical follow-up and abdominal ultrasound.The patients were examined at 7 days,1 month,3 months and 6 months after the operation and every 6 months after the operation,and continue d until death,loss of follow-up or the end of the study(October 2020)or until the patients received TIPS or surgical treatment.Kaplan-Meier curves were used to calculate the 1-,2-,and 5-year survival rates and cumulative patency rates.Results The success rate of AHV and MHV was 100%.In AHV recanalization group,balloon dilatation was performed in 21 cases and stent implantation in 5 cases.In MHV recanalization group,there were 68 cases of balloon dilatation and 5 cases of stent implantation.The clinical success rates of AHV and MHV recanalization were 96.2%(25/26)and 94.5%(69/73),respectively,and there was no significant difference between them(P = 0.744).The levels of aspartate aminotransferase(P = 0.009),alanine aminotransferase(P = 0.015)and alkaline phosphatase(P < 0.001)were significa nt ly decreased in AHV group.The mean intralumina l pressure in AHV group decreased from 44.6 ± 5.8 cm H2 O preoperatively to 16.6 ± 5.1 cm H2 O postoperatively(P < 0.001).There was no significant difference in restenosis rate between AHV group and MHV group(20% vs.34.8%,P = 0.170).Univariate analysis showed that younger age,segmental venous obstruction,MHV recanalization,AHV / MHV thrombosis,elevated alkaline phosphatase level and low albumin level were the predictors of restenosis,but multivariate analysis showed that variables were not independent risk factors of restenosis.The cumulative patency rates at 1,2 and 5 years after the primary recanalization were 96.0%,91.6% and 76.3% in AHV group and 87.0%,78.6% and 58.6% in MHV group,respectively.There was significant difference between the two groups(P = 0.048).The cumulative patency rates at 1,2 and 5 years after the secondary recanalization were 96.0%,96.0% and 96.0% in AHV group and 97.1%,97.1% and 81.8% in MHV group,respectively.There was no significant difference between the two groups(P = 0.289).The 1-,2-,and 5-year cumulative survival rates of the two groups were 96.0% and 98.6%,96.0% and 95.2%,96.0% and 89.7%,respectively.There was no significant difference between the two groups(P = 0.462).Conclusion 1.Both AHV and MHV interventional treatment have high technica l and clinical success rates,which can be used as an effective treatment for hepatic vein type Budd-Chiari syndrome.2.The cumulative patency rate at 1,2 and 5 years after the primary recanalization in AHV group was significantly higher than that in MHV group,while the cumulative patency rate at 1,2 and 5 years after the secondary recanalization in AHV group was not significantly different from that in MHV group.3.Age,segmental venous obstruction,MHV recanalization,AHV / MHV thrombosis,elevated alkaline phosphatase level and low albumin level were predictive factors of restenosis,but not independent risk factors.4.The 2-year cumulative survival rates of both AHV and MHV group were higher than 95%.The 5-year cumulative survival rate of AHV group was slightly higher than MHV group,but the difference was not statistically significant.