Establishment and Assessment of the HVPG Using Biofluid Mechanics (HVPGBFM)
Phase: NA
Conditions: Liver Cirrhosis, Hypertension, Portal
Sponsor: Shanghai Ninth People's Hospital Affiliated to Shanghai Jiao Tong University

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ID: JYLJ021 
 
Clinical Research Program of Shanghai Ninth People's Hospital, 
Shanghai Jiao Tong University School of Medicine 
 
 
Establishment and Assessment of the 
HVPG using Biofluid Mechanics (HVPGBFM) 
 
 
Study Protocol and Statistical Analysis Plan 
 
 
Version: 1.3 
Date: December 12
th, 2018 
 
 

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Introduction 
Portal hypertension (PH), an increased blood pressure of the portal vein and its branches, is 
one of the most severe syndromes caused by chronic liver diseases. Hepatic venous pressure 
gradient (HVPG) is currently the gold standard to detect portal hypertension.(1) HVPG value 
greater than 5 mmHg is deﬁned as portal hypertension; HVPG value higher than 10 mmHg is 
considered as clinically signiﬁcant portal hypertension (CSPH), which is highly associated 
with hepatocellular carcinoma and severe complications including gastroesophageal variceal 
haemorrhage, hepatic encephalopathy and ascites.(2) 
However, the HVPG measurement is only available in few hospitals due to its invasiveness and 
technical difficulty.(3) In recent years, there are already several non-invasive portal 
hypertension assessment methods, including clinical examination, ultrasound, elastography, 
CT and MRI,(4) few of which, however, was proved to be accurate enough to replace the 
invasive HVPG measurement. Therefore, a less-invasive and accurate assessment method is 
needed and would be useful in the diagnosis and evaluation of portal hypertension. 
Biofluid mechanics is the study of mechanisms of biological flows (liquid and gas) and their 
interrelationships with physiological and pathological processes by using fundamental 
principles of fluid mechanics.(5) Fortunately, recent advances in biofluid mechanics and 
image-based modelling make it possible for cardiologists to calculate fractional flow reserve, 
which is the gold standard assessment of the haemodynamic significance of coronary 
stenoses.(6) Moreover, biofluid mechanics may offer a new method for physicians to make an 
accurate assessment of HVPG noninvasively. The aim of the present study is to establish and 
validate the HVPG using biofluid mechanics (HVPGBFM) model.  
 
Methods and analysis 
Study design overview 
This study is a prospective, non-controlled, multicentre trial in patients with cirrhosis or 
portal hypertension. 
 
Study population 
Consecutive patients scheduled for HVPG measurement for clinical indications at Shanghai 
Ninth People's Hospital, Renji Hospital and Xinhua Hospital Affiliated to Shanghai Jiao Tong 
University School of Medicine are screened daily for study eligibility. Recruitment began on 
March 20th, 2018 and will continue until 200 participants have been recruited. 
 
Inclusion criteria: 
⚫ 
Be at least 18 years of age. 
⚫ 
Patients with cirrhosis or portal hypertension, scheduled for HVPG measurement. 
 
Exclusion criteria: 
⚫ 
Female patients who are pregnant or nursing. 
⚫ 
Patients who are medically unstable, terminally or seriously ill, or patients whose clinical 
course is unpredictable. 
⚫ 
Patients with clinically unstable cardiac disease, for example, congenital heart defect, 

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arrhythmia, uncontrolled heart failure (NYHA Class IV). 
⚫ 
Patients with respiratory distress syndrome or clinically unstable pulmonary disease, for 
example, pulmonary hypertension, pulmonary emboli, pulmonary vasculitis, emphysema. 
⚫ 
Patients with severe coagulation disorders. 
⚫ 
Patients with unstable occlusive disease or thrombosis within the hepatic, portal, or 
mesenteric veins. 
⚫ 
Patients who are allergic to iodinated contrast. 
 
Ethics and informed consent 
The trial complies with the latest Declaration of Helsinki. Written informed consent form will 
be obtained from patients or patients’ legal guardian or patients’ next of kin before the study 
begins. All participants can quit the study at any time without penalty or impact on the 
treatment. The study protocol, statistical analysis plan, informed consent form and case report 
form have already been approved by Scientific Research Projects Approval Determination of 
Independent Ethics Committee of Shanghai Ninth People's Hospital Affiliated to Shanghai Jiao 
Tong University School of Medicine. (Approval Number: 2017-430-T326) 
 
Objectives 
The primary objective of this study is to determine the numeric correlation between HVPGBFM 
and HVPG. The secondary objective is to determine the diagnostic accuracy of HVPGBFM for the 
diagnostics of PH and CSPH. The gold standard for the diagnosis will be the HVPG 
measurement. 
 
Procedure of the study 
Consecutive patients are randomly assigned 1:1 to either the original cohort or the validation 
cohort. Randomization is based on the computer-generated random digits table. This study 
consists of two independent and consecutive stages: 
1. 
Establishment and improvement of the HVPGBFM model: For 100 patients in the original 
cohort, biofluid mechanics specialists will use each patient’s computed tomography, blood 
tests, Doppler ultrasound and HVPG results to adjust the parameters of the HVPGBFM model in 
order to make each patient’s HVPGBFM and HVPG values match well. 
2. 
Assessment of the HVPGBFM model: For 100 patients in the validation cohort, biofluid 
mechanics specialists will use each patient’s computed tomography, blood tests and Doppler 
ultrasound results to calculate each patient’s HVPGBFM according to the HVPGBFM model 
established previously. Biofluid mechanics specialists will make no changes to the HVPGBFM 
model and will have no access to patients’ HVPG results in this cohort. Finally, the researchers 
will compare each patient’s HVPGBFM and HVPG value and make an assessment of the HVPGBFM 
model. 
Each patient’s HVPG measurement will be performed after finishing computed tomography, 
blood tests and Doppler ultrasound. These results and other clinical data will be inaccessible 
to professionals for HVPG measurements in order to prevent certain biases. Each patient’s 
computed tomography, blood tests, Doppler ultrasound and HVPG measurement will be 
performed within 30 days and treatments that may affect HVPG value will be avoided during 
this period. 

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The study design and procedure are shown in Figure 1. 
Potentially eligible participants
n=
Eligible participants
n=
Excluded
n=
-Reason 1 (n=  )
-Reason 2 (n=  )
CT, blood tests, Doppler ultrasound
n=
No CT, blood tests, Doppler ultrasound
n=
-Reason 1 (n=  )
-Reason 2 (n=  )
HVPG measurement
n=
 No HVPG measurement
n=
-Reason 1 (n=  )
-Reason 2 (n=  )
Establish and improve
the HVPGBFM model
Eligible participants
n=
CT, blood tests, Doppler ultrasound
n=
No CT, blood tests, Doppler ultrasound
n=
-Reason 1 (n=  )
-Reason 2 (n=  )
HVPG measurement
n=
 No HVPG measurement
n=
-Reason 1 (n=  )
-Reason 2 (n=  )
Assess 
the HVPGBFM model
Original cohort
Validation cohort
 
Figure 1 Study design and procedure. 
 
Examination 
Computed Tomography 
Each patient will undergo an abdominal contrast-enhanced computed tomography (CT) by 
multi-detector row CT scanners according to the protocol.(7, 8) The following parameters will 
be used: voltage, 120 kVp; current, automatic; collimation, 1.24-1.25 mm; Slice thickness, 
0.625-2.5 mm; Slice interval, 1.0-2.0 mm; Matrix size, 512 × 512; rotation time, 0.5 s. A 
nonionic iodinated contrast agent (600 mg of iodine per kilogram of body weight, 300-370 mg 

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of iodine per ml, 3-5 ml per second) will be injected. Portal venous phase imaging will be 
performed 60-70 seconds after the beginning of intravenous contrast injection. 
Blood tests 
Each patient’s blood samples will be collected from the cubital vein for blood viscosity test and 
density measurement. The blood viscosity test will be done by a ZL9100C blood rheology 
analyser (Zhongchi, China). The blood density will be done by weighing one millilitre of blood: 
one millilitre of blood will be pipetted by a Thermo Scientific™ Finnpipette™ F1 Pipettor onto 
a YP-B2002 electronic balance (Guangzheng, China) for weight measurement. The blood 
density measurements will be repeated at least three times and then be averaged. 
Doppler Ultrasound 
Each patient will undergo an abdominal Doppler ultrasound scan to measure the inner 
diameters and the maximum blood flow velocity of the inferior vena cava, the hepatic veins, 
the portal vein and its main branches after an overnight fast. The 12 measurement positions 
are: right branch of the portal vein, left branch of the portal vein, the portal vein, proximal part 
of the splenic vein, distal part of the splenic vein, the superior mesenteric vein, the inferior 
mesenteric vein, the right hepatic vein, the middle hepatic vein, the left hepatic vein, the 
suprahepatic inferior vena cava and the infrahepatic inferior vena cava. Each measurement 
will be done during deep inspiration breath-hold. All measurements will be repeated at least 
twice and then be averaged. 
HVPG Measurement 
HVPG will be measured by professionals according to established standards.(3) After finishing 
the computed tomography, blood tests and Doppler ultrasound, each patient will undergo an 
HVPG measurement after an overnight fast and local anaesthesia. The right internal jugular 
vein will be cannulated using a 6-French introducer (TERUMO Radifocus RS*A60K10SQ, Japan) 
under ultrasonographic guidance, then a 5.5-French compliant balloon-tipped catheter 
(Edwards Lifesciences Fogarty 12TLW805F35, USA) connected with a pressure monitoring 
set (Edwards Lifesciences TruWave PX260, USA) will be guided into the right or middle 
hepatic vein for the measurement of wedged hepatic venous pressure (WHVP) and free 
hepatic venous pressure (FHVP). WHVP will be measured when inflating the balloon to totally 
occlude the hepatic vein; FHVP will be measured when placing the catheter tip freely in the 
hepatic vein, at approximately 3 cm from its opening into the inferior vena cava. All 
measurements will be taken at least in duplicate and HVPG will be calculated from the 
difference between average WHVP and average FHVP. HVPG = WHVP - FHVP. 
 
Computation 
Geometry 
Biofluid mechanics specialists will use IQQA-Liver software (version 2.0, EDDA Technology, 
Inc., USA) to convert the CT images from Digital Imaging and Communications in Medicine 
(DICOM) format files into stereolithography (STL) format files and create the simulation 
model of blood flow area in blood vessels accordingly. The model surface will then be meshed 
into triangle surface grids, each measuring from 0.2-1.0 mm, and the body meshes will be 
created accordingly. One case is shown in Figure 2. 

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Figure 2 An example of the simulation model of a portal venous system and its body meshes. (A) 
The simulation model of a portal venous system. (B) The body meshes of the simulation model. 
Physical property 
Biofluid mechanics specialists will use the blood viscosity of different shear forces (high, 
medium and low) to calculate the overall viscosity (Formula 1). Define a, b and c (a + b + c = 
1) as weighting coefficients. 
Formula 1: 
𝑜𝑣𝑒𝑟𝑎𝑙𝑙 𝑣𝑖𝑠𝑐𝑜𝑠𝑖𝑡𝑦= 𝑎× 𝑣𝑖𝑠𝑐𝑜𝑠𝑖𝑡𝑦ℎ𝑖𝑔ℎ+ 𝑏× 𝑣𝑖𝑠𝑐𝑜𝑠𝑖𝑡𝑦𝑚𝑒𝑑𝑖𝑢𝑚 + 𝑐×
𝑣𝑖𝑠𝑐𝑜𝑠𝑖𝑡𝑦𝑙𝑜𝑤 
Boundary conditions 
Biofluid mechanics specialists calculate the blood flow velocity at the boundaries of the main 
blood vessels according to the maximum blood flow velocity (measured by Doppler 
ultrasound), the inner diameter (obtained from the STL format files) and the principle of mass 
conservation (Formula 2). Define d (0.7<d<1) as the maximum blood flow velocity 
attenuation coefficient. One case is shown in Figure 3. 
Formula 2: 
𝑎𝑣𝑒𝑟𝑎𝑔𝑒 𝑏𝑙𝑜𝑜𝑑 𝑓𝑙𝑜𝑤 𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦= 𝑑× 𝑏𝑙𝑜𝑜𝑑 𝑓𝑙𝑜𝑤 𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦𝑚𝑎𝑥𝑖𝑚𝑢𝑚 
 
Figure 3 An example of the blood flow velocity of the portal vein and its branches. 
The Navier-Stokes equations 
The whole blood can be assumed to be an incompressible Newtonian fluid and blood flow can 
be modelled by the Navier-Stokes equations as follows: 
Formula 3: 
𝜕𝜌
𝜕𝑡+ 𝛻∙(𝜌𝑣⃗) = 𝑆𝑚 
Formula 4: 
𝜕𝜌
𝜕𝑡+
𝜕
𝜕𝑥(𝜌𝑣𝑥) +
𝜕
𝜕𝑟(𝜌𝑣𝑟) +
𝜌𝑣𝑟
𝑟= 𝑆𝑚 

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Formula 5: 
𝜕
𝜕𝑡(𝜌𝐸) + 𝛻∙(𝑣⃗(𝜌𝐸+ 𝑝)) = 𝛻∙(𝑘𝑒𝑓𝑓𝛻𝑇−∑ℎ𝑗
𝑗
𝐽⃗𝑗+ (𝜏̿𝑒𝑓𝑓∙𝑣⃗)) + 𝑆ℎ 
Formula 6: 
𝐸= ℎ−
𝑝
𝜌+
𝑣2
2  
Formula 7: 
𝜕
𝜕𝑡(𝜌𝑣⃗) + 𝛻∙(𝜌𝑣⃗𝑣⃗) = −𝛻𝑝+ 𝛻∙(𝜏̿) + 𝜌𝑔⃗+ 𝐹⃗ 
Formula 8: 
𝜏̿ = 𝜇[(𝛻𝑣⃗+ 𝛻𝑣⃗𝑇) −
2
3 𝛻∙𝑣⃗𝐼] 
ρ: density; v: velocity; Sm: mass added to the continuous phase; x: axial coordinate; r: radial 
coordinate; vx: axial velocity; vr: radial velocity; h: enthalpy value; p: static pressure; 𝜏̿: stress 
tensor; 𝑝𝑔⃗ : gravitational body force; 𝐹⃗ : external body force; μ: molecular viscosity; I: unit 
tensor. 
Establishment and improvement of the HVPGBFM model in the original cohort 
Empirical coefficients in initial: a = 0.05; b = 0.05; c = 0.9; d = 1. Calculate the overall viscosity 
and average blood flow velocity (formula 1 & 2) of one patient in the original cohort. Use the 
FLUENT software (version 6.3, ANSYS, Inc., USA) to solve the Navier-Stokes equations 
(formula 3-8) and get the simulated blood pressure on each volume grid. One case is shown 
in Figure 4. The simulated HVPG will be calculated from the difference between simulated 
portal pressure (PPBFM) and simulated hepatic venous pressure (HVPBFM), namely, HVPGBFM = 
PPBFM - HVPBFM. Compare the simulated and measured HVPG. If they don’t match well (their 
difference greater than 5%), then modify the value of a, b, c and d until they do. Record the 
value of a, b, c and d and the whole process for one patient is completed. Apply this process to 
each patient in the original cohort and record the value of a, b, c and d of each patient. 
 
Figure 4 An example of the blood pressure of the portal vein and its branches. 
Divide all patients into 9 groups according to their overall blood viscosity (high, medium and 
low) and their average blood flow velocity (high, medium and low): HighVis&HighVel, 
HighVis&MidVel, 
HighVis&lowVel, 
MidVis&HighVel, 
MidVis&MidVel, 
MidVis&lowVel, 
LowVis&HighVel, LowVis&MidVel, LowVis&lowVel. Calculate the statistical mean value of a, b, 
c and d of each group. 
Calculation of the HVPGBFM in the validation cohort 
First, determine each patient’s group according to the blood viscosity and blood flow velocity. 
Secondly, use the value of a, b, c and d of the specific group to calculate the geometry, physical 
property and the boundary conditions of each patient. Thirdly, use the FLUENT software to 
solve the Navier-Stokes equations and get the simulated blood pressure on each volume grid. 

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Finally, calculate the HVPGBFM. 
The summarized computation process is shown in Figure 5. 
Empirical coefficients in initial
Compute geometry, physical property 
and boundary conditions
Calculate HVPGBFM
Record each patient's coefficients
Group all the patients
Calculate each group's coefficients
Determine each patient s group
Use the coefficients of the group
Original cohort
Validation cohort
HVPGBFM and HVPG 
match well?
Yes
No
Modify coefficients
Compute geometry, physical property 
and boundary conditions
Calculate HVPGBFM
 
Figure 5 The process of the HVPGBFM computation 
 
Sample size calculation 
There will be 9 groups in the model. In order to obtain a precise model, no less than 10 samples 
for each group is needed in the original cohort, so the sample size estimated for the original 
cohort is 90 patients. It is anticipated that 10% of the patients recruited are likely to be 
excluded due to various reasons and therefore the target recruitment for the original cohort 
is 100 patients. The same number of patients will be recruited for the validation cohort. The 
total sample size is 200 patients. 
 
Statistical Analysis Plan 
Discrete variables will be summarized by frequencies and percentages and analysed by the χ2 

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test. Continuous variables will be checked for normal distribution and summarized by either 
mean and standard deviations or median and interquartile range as appropriate. Comparison 
of continuous variables will be performed by using Student’s t-test or ANOVA for normally 
distributed variables and the Mann-Whitney U test or Kruskal-Wallis test for non-normally 
distributed variables as appropriate. 
The numeric correlation between HVPGBFM and HVPG will be analysed by using Bland and 
Altman’s limits of agreement analysis.(9) Bias is defined as the mean of the difference between 
HVPGBFM and HVPG. Upper and lower limits of agreement are defined as average difference ± 
1.96 standard deviation of the difference. The numeric relationship between HVPGBFM and 
HVPG will also be analysed with linear regression analysis, and to visualize the results, 
HVPGBFM will be plotted against HVPG. 
The diagnostic accuracy of HVPGBFM for the diagnostics of PH (HVPG ≥ 5 mmHg) and CSPH 
(HVPG ≥ 10 mmHg) will be assessed by its sensitivity (Se), specificity (Sp), false-negative rate 
(FNR), false positive rate (FPR), positive predictive value (PPV), negative predictive value 
(NPV), diagnostic accuracy, Youden index (YI), likelihood ratio (LR+ and LR-) and Cohen's 
Kappa. 
All tests of significance will be at the 5% significance level. Analyses will be conducted using 
SPSS Statistics (version 24.0, IBM, USA) and MedCalc Statistical Software (version 18.11, 
MedCalc Software bvba, Belgium). 
 
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