CPM Specifications Document Fontan tunnel Fontan incorporates the wall of the atrium with a baffle...

CPM Specifications Document

Fontan: OSMSC 0125_0000, 0126_0000

May 1, 2013

Version 1

Open Source Medical Software Corporation

© 2013 Open Source Medical Software Corporation. All Rights Reserved.

© 2013 Open Source Medical Software Corporation. All Rights Reserved. Page 2

1. Clinical Significance & Condition Congenital heart defects are structural abnormalities present at birth that disrupt normal blood flow through

the heart, affecting 8 of every 1,000 newborns [1]. There are at least 18 documented types of congenital heart

defects, including coarcataion of the aorta, single ventricle defects, and complete atrioventricular canal defect

[2]. A large amount of anatomical variation is present within these individual congenital heart defect types.

In a study that examined congenital heart disease in the general population, the prevalence of single ventricle

defects was found to be 0.13 per 1000 children and 0.03 per 1000 adults [3]. Single ventricle defects cover a set

of cardiac abnormalities that result in one of the two ventricles being underdeveloped. With one ventricle being

of inadequate functionality or size, only one ventricle is available to pump the blood throughout the entire body.

Some examples of single ventricle defects include: hypoplastic left heart syndrome, pulmonary atresia, tricuspid

atresia, and double inlet left ventricle [2] [4]. Single ventricle heart patients are severely cyanotic at birth, and

these conditions are fatal with no interventions.

In order to provide adequate oxygenation, and separate the pulmonary and

systemic blood supplies, the blood returning to the heart is surgically redirected

to the pulmonary arteries, bypassing the heart. This surgical course typically

consists of three staged surgeries, a Blalock Taussig (BT) shunt and/or Norwood

procedure, a Glenn procedure, and finally a Fontan procedure (or total

cavopulmonary connection, TCPC).

The first stage is performed immediately after birth, and can vary among

patients depending on the defect and the pulmonary resistances. A systemic-

pulmonary shunt (BT shunt, central shunt, or Sano shunt) is used to maintain

adequate ventricle volume load and providing sufficient pulmonary blood flow.

This is accomplished by connecting a systemic artery, such as the brachocephalic artery, to the pulmonary

arteries with a tube graft (Figure 1) [4] [5]. For situations where there is too much blood flow to the lungs, the

pulmonary artery can be narrowed with a synthetic band to restrict blood flow [4]. In patients with aortic

atresia, a neo-aorta is also constructed during the first stage of surgery. About 65-80% of hypoplastic left

ventricles have been found to be related to aortic atresia in several reviews [6]. During reconstruction of a neo-

aorta, the distal stump of the pulmonary artery and homograft tissue are used to

direct flow through the ascending aorta to the carotid and subclavian arteries [6, 7].

The second stage is typically completed between the ages of 2-6 months [5]. The

Glenn procedure connects the superior vena cava to the right pulmonary artery in

order to improve oxygenation and decrease ventricle volume load (Figure 2) [8]. If

the patient had previously gone through a stage one procedure, it is removed during

stage two [4]. Oxygen saturation in patients who have undergone the Glenn

procedure typically is between 75-85% [4]. Another variation of the second stage is

the hemi-Fontan, where the pulmonary artery and superior vena cava are connected

through the right atrium and closed off to the rest of heart with a patch.

Figure 1 –Systemic-pulmonary shunt for a single ventricle heart.

Figure 2 –Glenn procedure. Arrows represent blood flow, with blue being deoxygenated blood, red being oxygenated blood, and purple being a mix of both.


The third stage, a complete Fontan procedure, is typically completed between the ages of 1-5 years [5]. This

final stage redirects the inferior vena cava to the pulmonary artery. In combination with the previous stage,

deoxygenated blood bypasses the heart completely and is routed directly to the pulmonary artery so the single

ventricle is only pumping oxygenated blood throughout the body. A complete Fontan procedure is typically

done through a lateral tunnel or extracardiac method. A lateral

tunnel Fontan incorporates the wall of the atrium with a baffle

from the inferior vena cava to the pulmonary artery. On the

other hand, an extracardiac Fontan connects the inferior vena

cava to the pulmonary artery with a synthetic tube-shaped graft,

bypassing the heart altogether (Figure 3) [4]. In both methods, a

small hole, or fenestration, is often needed between the newly

formed channel and the atrium to reduce pressure in the Fontan

circuit [4] [5]. A complete Fontan procedure increases oxygen

saturation to virtually normal levels [4].

2. Clinical Data Patient-specific volumetric image data was obtained to create physiological models and blood flow simulations.

Details of the imaging data used can be seen in Table 1. See Appendix 1 for details on image data orientation.

Table 1 – Patient-specific volumetric image data details (mm)

OSMSC ID Modality Voxel Spacing Voxel Dimensions Physical Dimensions

R A S R A S R A S

0125_0000 MR 1.0 0.5859 0.5859 112 512 512 112 300 300

0126_0000 MR 1.3 0.6836 0.6836 112 512 512 145.6 350 350

Available patient-specific clinical data collected can be seen in Table 2.

Table 2 – Available patient-specific clinical data

OSMSC ID Age Gender Height Weight BSA CI PA

Flow (L/min)

IVC Pavg

(mmHg)

LPA Pavg

(mmHg)

RPA Pavg

(mmHg)

SVC Pavg

(mmHg)

0125_0000 5 M 1.15 23.4 0.86 - - - - - -

0126_0000 9 M 1.4 48 1.38 4.28 4.6 11 12 12 12

Figure 3 – Complete Fontan Circulation: Laterial Tunnel Fontan (leff), Extracardiac Fontan (right). Arrows represent blood flow, with blue being deoxygenated blood and red being oxygenated blood.


Details for available PCMRI can be seen in Table 3.

Table 3 – Available PCMRI

OSMSC ID Slice Location Number of Frames Voxel Spacing (mm)

X Y

0125_0000

IVC 20 0.937492 0.937494

LPA 20 0.937502 0.937498

LPA 20 0.937502 0.937498

RPA 20 0.937498 0.9375

RPA 20 0.937498 0.9375

IVC 20 0.937492 0.937494

SVC 20 0.937493 0.937498

SVC 20 0.937493 0.937498

0126_0000

Aorta 20 0.9375 0.9375

Aorta_v2 20 0.9375 0.9375

SVC 20 0.9375 0.9375

IVC 20 0.9375 0.9375

IVC_v2 20 0.9375 0.9375

RPA 20 0.9375 0.9375

LPA 20 0.9375 0.9375

3. Anatomic Model Description Anatomic models were created using customized SimVascular software (Simtk.org) and the image data

described in Section 2. See Appendix 2 for a description of modeling methods. See Table 4 for a visual summary

of the image data, paths, segmentations and solid model constructed.

Table 4 – Visual summary of image data, paths, segmentations and solid model.

OSMSC ID Image Data Paths Paths and

Segmentations Model

ID:

OSMSC0125

subID: 0000

Age: 5

Gender: M


ID:

OSMSC0126

subID: 0000

Age: 9

Gender: M

Details of anatomic models, such has number of outlets and model volume, can be seen in Table 5.

Table 5 – Anatomic Model details

OSMSC ID Inlets Outlets Volume (cm3) Surface Area (cm2) Vessel Paths 2-D Segmentations

0125_0000 3 23 25.9053 118.341 25 101

0126_0000 3 31 39.1081 156.933 34 122

4. Physiological Model Description

In addition to the clinical data gathered for this model, several physiological assumptions were made in

preparation for running the simulation. See Appendix 3 for details.

5. Simulation Parameters & Details

5. 1 Simulation Parameters

See Appendix 4 for information on the physiology and simulation specifications. Solver parameters can be seen

in Table 6. Table 6 – Solver Parameters

OSMSC ID Time Steps per Cycle Time Stepping Strategy

0125_0000 2000 Residual Control - Min: 2, Max: 6, Criteria: 0.0001

0126_0000 2000 Residual Control - Min: 2, Max: 6, Criteria: 0.0002

5. 2 Inlet Boundary Conditions PCMRI data was used to generate flow waveform to be applied to the inlets of the computation fluid dynamics

(CFD) model (Figure 4). See Table 7 for more inflow details.


Table 7 – Details for waveforms seen in Figure 4

OSMSC ID Period (sec) Mean Flow (L/sec) Profile Type

SVC IVC LIV Total

0125_0000 2.86 1.07434 1.02607 0.460408 2.560818 Womersley

0126_0000 2.86 0.742974 2.33086 0.583819 3.657653 Womersley

Figure 4 – Inflow waveforms in L/min

5. 3 Outlet Boundary Conditions

RCR boundary conditions were applied to each outlet. Initial LPA/RPA flow splits were prescribed as seen in

Table 8, with a 20:40:40 split between the upper, middle, and lower lobes, respectively, for both the left and

right pulmonary artery. See Appendix 5 for more details on RCR calculations and Exhibit 1 for the values used in

each simulation.

Table 8 – LPA and RPA Flow Splits from PCMRI

OSMSC ID LPA RPA

0125_0000 52% 48%

0126_0000 50% 50%

6. Simulation Results

Simulation results were quantified for the last cardiac cycle. Paraview (Kitware, Clifton Park, NY), an open-

source scientific visualization application, was used to visualize the results. A volume rendering of velocity

magnitude for three time points during the cardiac cycle can be seen in Table 10 for each model.


Table 9 – Volume rendering velocity during max flow and min flow.

OSMSC ID Max Flow Min Flow

ID:

OSMSC0125

subID: 0000

Age: 5

Gender: M

ID:

OSMSC0126

subID: 0000

Age: 9

Gender: M

Surface distribution of time-averaged blood pressure (TABP), time-averaged wall shear stress (TAWSS) and

oscillatory shear index (OSI) were also visualized and can be seen in Table 10.

Table 10 – Time averaged blood pressure (TABP), time-average wall shear stress (TAWSS), and oscillatory shear index (OSI) surface distributions

OSMSC ID TABP TAWSS OSI

ID: OSMSC0125

subID: 0000

Age: 5

Gender: M

ID: OSMSC0126

subID: 0000

Age: 9

Gender: M


7. References

[1] National Heart Blood and Lung Institute, "Congenital Heart Defects," 1 July 2011. [Online]. Available:

http://www.nhlbi.nih.gov/health/health-topics/topics/chd/. [Accessed January 2012].

[2] American Heart Association, "Common Types of Heart Defects," 2 May 2011. [Online]. Available:

http://www.heart.org/HEARTORG/Conditions/CongenitalHeartDefects/AboutCongenitalHeartDefects/Common-

Types-of-Heart-Defects_UCM_307017_Article.jsp#.TwHuCNQS01I. [Accessed Januaray 2012].

[3] A. Marelli, A. Mackie, R. Ionescu-Ittu, E. Rahme and L. Pilote, "Congenital Heart Disease in the General

Population: Changing Prevalence and Age Distribution," Circulation, vol. 115, pp. 163-172, 2007.

[4] Cincinnati Children's, "Single Ventricle Anomalies and Fontan Circulation," March 2010. [Online]. Available:

http://www.cincinnatichildrens.org/health/s/sv/. [Accessed January 2012].

[5] S. Nayak and P. Booker, "The Fontan Circulation," British Journal of Anaesthesia, vol. 8, no. 1, pp. 26-30, 2008.

[6] A. M. Rudolph, "Aortic atresia, mitral atresia, and hypoplastic left ventricle," in Congenital Disease of the Heart:

Clinical Physioloical Considerations, Hoboken, Blackwell Publishing, 2009, pp. 257-288.

[7] Children's Hospital of Wisconsin, "Norwood Procedure of Hypoplastic Left Heart Syndrome," 2012. [Online].

Available: http://www.chw.org/display/router.asp?DocID=21364#. [Accessed 24 May 2012].

[8] S. Yuan and H. Jing, "Palliative Procedures for Congenital Heart Defects," Archives of Cardiovascular Disease, vol.

102, pp. 549-557, 2009.


Exhibit 1: Simulation RCR Values

Table 11 – RCR values for 0125_0000 in cgs units

ID Face Name Rp C Rd

2 RPA_b5_1 795.21 3.84E-05 4278.09

3 RPA_b5 700.61 3.99E-05 4152.12

4 RPA_b1 1362.26 2.03E-05 6662.18

5 RPA_b3 1619.34 1.63E-05 8235.24

6 RPA_b8 1556.05 1.59E-05 8474.50

7 RPA_b2 642.96 5.55E-05 2720.58

8 RPA_b6 1780.52 1.31E-05 10473.93

9 RPA_b7 1011.46 2.06E-05 6341.21

10 RPA_b9 715.59 6.59E-05 2481.22

11 RPA_b4 1219.51 2.10E-05 6321.69

12 RPA 1011.46 2.06E-05 6341.21

13 LPA_b1 791.95 3.98E-05 4098.00

14 LPA_b1_1 1118.42 2.33E-05 5556.76

15 LPA_b2 773.47 3.96E-05 3671.79

16 LPA_b8 1070.78 2.07E-05 6337.99

17 LPA_b4 1428.06 1.79E-05 7303.71

18 LPA_b5 953.74 3.39E-05 4248.16

19 LPA_b3 1139.10 2.23E-05 5846.31

20 LPA_b7 662.87 6.96E-05 2253.45

21 LPA_b6 914.74 2.88E-05 5373.57

22 LPA_b6_1 858.61 3.93E-05 3613.08

23 LPA_b9 829.83 3.58E-05 4608.71

24 LPA 420.92 9.07E-05 1766.32


Table 12 – RCR values for 0126_0000 in cgs

ID Face Name Rp C Rd

31 LPA 635.99 5.58E-05 2931.12

32 LPA1 1850.37 9.55E-06 13592.59

30 LPA2 1125.65 1.99E-05 6691.16

15 LPA3 1532.24 1.81E-05 7302.35

21 LPA4 777.81 4.15E-05 3950.48

24 LPA5 3379.32 4.64E-06 24149.44

23 LPA6 1525.55 1.10E-05 12090.83

19 LPA7 823.92 3.22E-05 4726.68

20 LPA8 823.92 3.22E-05 4726.68

29 LPA21 1953.41 9.70E-06 13875.63

28 LPA22 4372.41 2.82E-06 39293.90

26 LPA23 2235.63 7.04E-06 16664.71

27 LPA24 2360.14 6.68E-06 18064.43

13 LPA31 1413.65 1.31E-05 9144.76

17 LPA32 1617.06 1.11E-05 11115.14

16 LPA33 921.13 2.86E-05 5444.97

22 LPA41 867.49 3.19E-05 4806.46

25 LPA51 2652.98 4.54E-06 24290.06

18 LPA71 646.87 6.01E-05 2466.88

14 LPA311 2114.32 7.25E-06 15922.96

11 RPA 838.34 4.13E-05 3756.44

9 RPA1 784.42 4.04E-05 3591.56

10 RPA2 1128.13 1.99E-05 6716.62

4 RPA3 438.14 7.89E-05 1967.88

6 RPA4 1536.07 1.69E-05 7932.77

2 RPA5 769.69 4.71E-05 3247.62

8 RPA6 1648.20 1.11E-05 12038.39

12 RPA7 867.79 3.19E-05 4809.79

5 RPA31 693.22 8.86E-05 1951.23

7 RPA41 1710.73 1.34E-05 10030.63

3 RPA51 724.33 5.20E-05 3038.89


Appendix

1. Image Data Orientation The RAS coordinate system was assumed for the image data orientation. Voxel Spacing, voxel dimensions, and

physical dimensions are provided in the Right-Left (R), Anterior-Posterior (A), and Superior-Inferior (S) direction

in all specification documents unless otherwise specified.

2. Model Construction All anatomic models were constructed in RAS Space. The models are generated by selecting centerline paths

along the vessels, creating 2D segmentations along each of these paths, and then lofting the segmentations

together to create a solid model. A separate solid model was created for each vessel and Boolean addition was

used to generate a single model representing the complete anatomic model. The vessel junctions were then

blended to create a smoothed model.

3. Physiological Assumptions Newtonian fluid behavior is assumed with standard physiological properties. Blood viscosity and density are

given below in units used to input directly into the solver.

Blood Viscosity: 0.04 g/cm•s2

Blood Density: 1.06 g/cm3

4. Simulation Parameters Conservation of mass and Navier-Stokes equations were solved using 3D finite element methods assuming rigid

and non-slip walls. All simulations were ran in cgs units and ran for several cardiac cycles to allow the flow rate

and pressure fields to stabilize.

5. Outlet Boundary Conditions

5.1 Resistance Methods

Resistances values can be applied to the outlets to direct flow and pressure gradients. Total

resistance for the model is calculated using relationships of the flow and pressure of the model.

Total resistance is than distributed amongst the outlets using an inverse relationship of outlet area

and the assumption that the outlets act in parallel.

5.2 Windkessel Model

In order to represent the effects of vessels distal to

the CFD model, a three-element Windkessel model

can be applied at each outlet. This model consists of

proximal resistance (Rp), capacitance (C), and distal

resistance (Rd) representing the resistance of the

proximal vessels, the capacitance of the proximal

vessels, and the resistance of the distal vessels

downstream of each outlet, respectively (Figure 1).

Figure 5 - Windkessel model


First, total arterial capacitance (TAC) was calculated using inflow and blood pressure. The TAC was

then distributed among the outlets based on the blood flow distributions. Next, total resistance (Rt)

was calculated for each outlet using mean blood pressure and PC-MRI or calculated target flow

(Rt=Pmean/Qdesired). Given that Rt=Rp+Rd, total resistance was distributed between Rp and Rd adjusting

the Rp to Rt ratio for each outlet.

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CPM Specifications Document Fontan tunnel Fontan incorporates the wall of the atrium with a baffle...

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