Wenjun Wu, Dr. Ajit P. YoganathanCardiovascular Fluid Mechanics Lab, Georgia Tech, Atlanta, GA
Introduction
• Children born with singleventricle(SV)congenitalheartdefectshave singleventriclewith amixtureofoxygenatedanddeoxygenatedblood.• Fontan surgery finalizesinthetheTotalCavopulmonary Connection(TCPC)
IVC
SVCRPA
LPA
AfterTCPC
Surgery
NormalHeart
IVC
SVCLPARPA SVC
IVC
LPARPA
SingleVentricle
•AdversehemodynamicsintheTCPChavebeenrelatedtosomelongtermcomplications:• Limitedexercisecapacity:increasedresistancetoflowtowardsthelungsimposedbytheconnection,whichhasbeenlinkedtoTCPCpowerloss(PL)duringrestingcondition [1]
• Pulmonaryarteriovenousmalformations(PAVM):unevenhepaticflowdistribution(HFD)tothelungs
•ComputationalfluiddynamicshasbeenwidelyusedtounderstandcomplexFontanhemodynamicsandoptimizethesurgicalstrategies/connections.•Chronic changes are important since growth is unavoidable for our patients•Previous study has investigatedchronicchangeofenergydissipationofTCPC [2] ;• TheymarginallydiscussedchronicchangeofHepatic blood flowdistribution (HFD),whichisoneofimportantFontanhemodynamicmetrics.
Objective• Retrospectivelyanalyzesimulationsof33 serialFontanpatientsand
explorethechronicchangesofhepaticbloodflowdistributionoftheTCPC.
• Investigate therelationshipof chronic changes of Fontanhemodynamicsto patients’outcomes.
Results (Contd.)
Methods
TimePoint Age(yr) BodySurface
Area(m2)T1 11.8±4.5 1.31±0.41T2 17.4±4.5 1.65±0.29
PatientSelection• Completed Fontan surgery• had at least twoCMRscansindatabase (T1, T2)
• Completed questionnaireforqualityoflife.
Anatomical and Flow Reconstruction
Cardiovascular magneticResonance Image
acquisition
Result
Limitation and Future Work
• Blood flow in vessels are pulsatile,not steady.
• Future work will use pulsatileboundary conditions instead.
(a) Flow rate is not constant in acardiac cycle.
(b) Velocity Stream-traces of simulationresult using mean flow rateboundary condition
(c) Velocity Stream-traces of simulationresult under pulsatile boundarycondition at three time points
AcknowledgementVesselSegmentationfrom patient MRI [3]
ComputationalFluidDynamics(CFD)• MeshweregeneratedwithGambitorANSYSMeshingmodule• Patient-specificflowswereusedasboundaryconditions• In-houseimmersed-boundarymethodwasusedforsimulations• Bloodflow:assumedtobeNewtonian,density=1060kg/m3,viscosity=3.5×10-6 m2s-1
Quantificationofhemodynamics• PowerlosswasdefinedusingacontrolvolumeenergyanalysisoftheTCPC
wherePistotalpressureandQismeanflowateachinlet/outlet• HFDwasdefinedbythepercentageofIVCflowtotheleftpulmonaryartery,whichis
obtainedbyanin-houseparticletrackingcode
åå ´-´=outlets
outoutinlets
inin QPQPPL
Quality of Life (QoL) Score• QoL reflectstheimpactofaspecificillness,medicaltherapy,orhealthservicespolicyonthechild’sabilitytofunctioninsocietyanddrawpersonalsatisfactionfromaphysical,psychological,andsocialfunctioningperspective [4]
• Ahigher score meansa better perceived QoL[4]• QoLs wereonlytakenatT2
Statistics• Data normality: Anderson-Darling test• Statistical Test: T-Test, Linear Regression (Significance: p < 0.05)• Explored difference of QOL Score and HFD between different categories of patients (T-test)• Variablesincludedinstatisticalanalysesinclude:valuesattwotimepointsaswellasthe
chronicchanges of HFD, flows,andgeometriccharacteristicsofTCPC.
Patient specificanatomy and flowreconstruction [4]
Methods (Contd.)
Hepatic Flow Distribution
Type Time Points (T1, T2) Change between T2 and T1
HFD (in %) 52.6±21.2 54.3±23.1 1.7 ± 18.4
P -value 0.60 NA
Reference[1] Khiabani,R.H.,K.K.Whitehead,D.Han,M.Restrepo,E.Tang,J.Bethel,S.M.Paridon,M.a.Fogel,anda.P.Yoganathan.2015.“ExerciseCapacityinSingle-VentriclePatientsafterFontanCorrelateswithHaemodynamic EnergyLossinTCPC.”Heart101(2):139–43.[2]Frakes,D.H.,C.P.Conrad,T.M.Healy,J.W.Monaco,M.Fogel,S.Sharma,M.J.Smith,andA.P.Yoganathan,Applicationofanadaptivecontrolgridinterpolationtechniquetomorphologicalvascularreconstruction.IEEETransBiomedEng,2003.50(2):p.197-206.[3]Frakes,D.H.,M.J.Smith,J.Parks,S.Sharma,S.M.Fogel,andA.P.Yoganathan,NewtechniquesforthereconstructionofcomplexvascularanatomiesfromMRIimages.JCardiovasc Magn Reson,2005.7(2):p.425-32[4] Drotar,D.,MeasuringHealth-RelatedQualityofLifeinChildrenandAdolescents.1998:Mahwah,NewJersey:LawrenceErlbaumAssociates,Publishers.[5]Frakes,D.H.,M.J.Smith,D.A.deZélicourt,K.Pekkan,andA.P.Yoganathan,Three-dimensionalvelocityreconstruction.JBiomech Eng,2004.126(6):p.727-35.
Type Gender(Female,Male)
Fontan Type(EC, LT)
HLHS,non-HLHS
Bilateral,non-Bilateral
Reconstructed,non-
Reconstructed
∆HFD (in%)
-1.75±21.94.1±15.6
0.6±20.42.6±17.8
3.3±17.6-5.2±22.8
2.7±5.71.9±19.2
5.2±18.60.3±18.4
p values 0.38 0.78 0.35 0.95 0.49
R²=0.1899
-50 -40 -30 -20 -10 01020304050
-8 -6 -4 -2 0 2 4
∆HFD
(LPA
)inPercen
tage
Normalized SVC mean area
∆HFD(LPA) vs. ∆ NormalizedSVC mean area
R²=0.15611
-50 -40 -30 -20 -10 01020304050
-10 -5 0 5 10
∆HFD
(LPA
)inPercen
tage
Normalized SVC max area
∆HFD(LPA) vs. ∆ NormalizedSVC max area
y=-0.0496x+75.603R²=0.00116
0
20
40
60
80
100
120
0.00 10.00 20.00 30.00 40.00 50.00
QOLScore
change in % HFD
QoL Score vs ∆HFD
y=0.125x+68.308R²=0.02672
020406080100120
0.00 20.00 40.00 60.00 80.00 100.00 120.00
QOLScore
% HFD at T1
QoL Socre vs HFD at T1
y=0.1424x+64.694R²=0.03455
0
20
40
60
80
100
120
0.00 20.00 40.00 60.00 80.00 100.00 120.00
QOLScore
% HFD at T2
QoL Score vs HFD at T2 • According to R2 above, there is nodirect linear correlation between QOLScore, ∆HFD, HFD at T1 and HFD at T2.
• However, the simulation conductedusing steady flow boundary conditionmay not be accurate and importantinformation/characteristics may belost.
Theauthorsacknowledgethe mentorship from Dr. Zhenglun Wei. Thisworkwasmadepossiblethanksto National Heart, Lung and Blood Institute, NHLBIgrantsHL67622 andHL098252.
No difference in ∆HFD between patients in differentclinical categories
Quality of Life ScoreType Gender
(Female,Male)
FontanType (EC,
LT)
HLHS,non-HLHS
Bilateral,non-
Bilateral
Reconstructed,non-
Reconstructed
Overall
QOL
Score
75.0 ±12.6
78.4±10.7
73.0±13.3
78.3±10.7
77.5± 10.9
76.3±16.7
87.6±9.6
76.2±11.4
79.2±11.5
76.2±11.6
74.9±16.8
p values 0.4176 0.2523 0.8398 0.1070 0.4884 NA
No difference in QoL score between patients in different categories
