Cardiology in the Young 2011; Page 1 of 12doi:10.1017/S1047951111001491r Cambridge University Press, 2011Original ArticlePulsatile venous waveform quality affects the conduitperformance in functional and ‘‘failing’’ Fontan circulationsOnur Dur,1Ergin Kocyildirim,2Ozlem Soran,3Peter D. Wearden,2Victor O. Morell,2Curt G. DeGroff,4Kerem Pekkan1,51Department of Biomedical Engineering, Carnegie Mellon University;2Section of Pediatric Cardiothoracic Surgery ofthe Heart, Lung and Esophageal Surgical Institute, University of Pittsburgh Medical School, Children’s Hospital ofPittsburgh;3Cardiovascular Institute, University of Pittsburgh, Pittsburgh, Pennsylvania;4Congenital Heart Center,University of Florida, Gainesville, Florida;5Department of Mechanical Engineering, Carnegie Mellon University,Pittsburgh, Pennsylvania, United States of AmericaAbstract Objective: To investigate the effect of pulsatility of venous flow waveform in the inferior andsuperior caval vessels on the performance of functional and ‘‘failing’’ Font an pa tients based on two primaryperformance measures – the conduit power loss and the distribution of inferior caval flow (hepatic factors) tothe lungs. Methods: Doppler angiography flows were acquired from two typical extra-cardiac conduit ‘‘failing’’Fontan patients, aged 13 and 25 years, with ventricle dysfunction. Using computational fluid dynamics,haemodynamic efficiencies of ‘‘failing’’, functional, and in vitro-generated mechanicall y assisted venous flowwaveforms were evaluated inside an idealised total cavopulmonary connection with a caval offset. Toinvestigate the effect of venous pulsatility alone, cardiac output was normalised to 3 litres per minute in allcases. To quantify the pulsatile behaviour of venous flows, two new performance indices were suggested.Results: Variations in the pulsatile content of venous waveforms altered the conduit efficiency notably. High-frequency and low-amplitude oscillations lowered the pulsatile component of the power losses in ‘‘failing’’Fontan flow waveforms. Owing to the offset geometry, hepatic flow distribution de pended strongly on theratio of time-dependent caval flows and the pulsatility content rather than mixing at the junction. ‘‘Failing’’Fontan flow waveforms exhibited less balanced hepatic flow distribution to lungs. Conclusions: Thehaemodynamic efficiency of single-ventricle circulation depends strongly on the pulsatility of venous flowwaveforms. The proposed perform ance indices can be calculated easily in the clinical setting in efforts to betterquantify the energy efficiency of Fontan venous waveforms in pulsatile settings.Keywords: ‘‘Failing’’ Fontan patient; congenital cardiac disease; pulsatility index; computational fluid dynamics; power loss; hepatic flowdistributionReceived: 17 December 2010; Accepted: 17 July 2011THE THIRD STAGE FOR PALLIATIVE SURGICALreconstruction for children with functionalsingle-ventricle physiology is the completion ofthe total cavopulmonary connection, where the super -ior and inferior caval vessels are routed directly intothe pulmonary arteries.1This patient populationcontinues to grow, with approximately 5000 new-borns in the United States joining the existing single-ventricle patient population each year , along withincreasing numbers of adult Fontan patients survivinglonger because of the advances in surgical techniquesand post-operative management. Although most post-operative Fontan patients experience an acceptablequality of life, their lifespan is shorter than normal,with a significant number of these patients developingCorrespondence to: Dr K. Pekkan, PhD, Assistant Professor, BiomedicalEngineering Department, Carnegie Mellon University, 700 Technology Drive,Pittsburgh, Pennsylvania 15219, United States of America. Tel: 412 268 3027;Fax: 404 268 9807; E-mail: [email protected] haemodynamic complications.2,3Unfortunately,for many Fontan patients, cardiac transplantation hasnow become their final ‘‘stage’’ option.Following the single-ventricle palliation, there isincreased afterload and decreased preload reserve inthe Fontan circulation. This requires low pulmonaryvascular resistance, which is associated with the calibreof the main pulmonary arteries and downstreamvasculature, to alleviate the low cardiac output state.4,5Surgical pathway resistance is an integral piece ofpulmonary vascular resistance, and in some functionalpatients it can be as high as the pulmonary vascularresistance, which would affect the cardiac output non-linearly, with further consequences at exercise.6Bothour earlier in vitro physiological bioengineering models7and recent clinical studies8,9suggest that Fontanphysiology necessitates vascular remodelling towardsstiffer venous compliance to restore the normal cardiacoutput. The absence of direct ventricular assistance forpulmonary blood flow along with these altered venouscharacteristics suggests that optimisation of the Fontanpathway haemodynamics may improve patient out-comes. Most of the published efforts to date havefocused on minimising energy losses within Fontanconnections.10–13An extensive review of these studieshas been provided by our group.14Efforts to quantifythe steady-state energy losses inside patient-specifictotal cavopulmonary connection geometries6,11,15iden-tified non-dimensional power -loss metrics that dependon steady-state pathway flow rate – cardiac output;patient body surface area – total cavopulmonaryconnection size; secondary anatomical features – offset,flare, etc.; and pulmonary flow split.16As demon-strated in this study, the non-dimensional formulationallows performing parametric studies, where the effectof a particular metric , that is, cavopulmonary flowpulsatility, can be investigated by fixing each otherparameter, that is, cardiac output, flow splits, andsurgical design dimensions.Pulsatile flow simulations incorporating phase-contrast magnetic resonance image measurementshave recently been used in pre-surgical planningapplications.17,18Nevertheless, limited attention has beengiven to the real-time ‘ ‘pulsatile’’ venous flow characteristics ofthe cavopulmonary pathway associated with the pronouncedrespiratory effects within the single-ventricle circulation.19Our recent experimentally validated pulsatile compu-tational investigations with real-time pulsatile cavalwaveforms suggest that for fixed cardiac output, energyloss is