title: Hemodynamic effects of implanting a unidirectional valve in the inferior vena cava of the Fontan circulation pathway: an in vitro investigation.
abstract: The Fontan surgical procedure used for treating patients with single ventricle congenital heart disorders results in a total cavopulmonary connection (TCPC) of the vena cavae to the pulmonary arteries (PAs). Sluggish TCPC flow and elevated hepatic venous pressures are commonly observed in this altered physiology, which in turn can lead to long-term complications including liver congestion and cirrhosis. The hypothesis of this study is that placement of a unidirectional valve within the inferior vena cava (IVC) will improve hemodynamics of the Fontan circulation by preventing retrograde flow and lowering hepatic venous pressure. An in vitro experimental setup consisting of an idealized TCPC model with flexible walls was used for investigation, and a bovine venous valve was inserted in the IVC below the TCPC. Pressure fluctuations were introduced in the flow through the model to simulate venous pulsatility. Hemodynamics of baseline and valve-implanted conditions were compared across total caval flows ranging from 1.0 to 2.5 l/min with varying caval flow distributions. The results indicated that valve closure occurred for 15-20% of the total cycle, with consequent reduction in the upstream hepatic venous pressure by 5 to 10 mmHg. Energy loss (EL) through the TCPC was lowered with valve implantation to 20-50% of baseline, occurring across all flow conditions considered with mean caval and PA pressures greater than 10 mmHg. The results of this in vitro modeling suggest that IVC valve placement has the potential to improve hemodynamics in the Fontan circulation by decreasing hepatic venous hypertension and EL.
authors.affiliation: The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia;
authors.forename: Arvind
authors.initials: A
authors.lastname: Santhanakrishnan
authors.forename: Kevin O
authors.initials: KO
authors.lastname: Maher
authors.forename: Elaine
authors.initials: E
authors.lastname: Tang
authors.forename: Reza H
authors.initials: RH
authors.lastname: Khiabani
authors.forename: Jacob
authors.initials: J
authors.lastname: Johnson
authors.forename: Ajit P
authors.initials: AP
authors.lastname: Yoganathan
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D001783:Blood Flow Velocity; D002417:Cattle; D057510:Endovascular Procedures; D018729:Fontan Procedure / Q000009:adverse effects; D006439:Hemodynamics; D006503:Hepatic Veins / Q000503:physiopathology*; D008953:Models, Anatomic; D008955:Models, Cardiovascular; D011673:Pulsatile Flow; D012039:Regional Blood Flow; D014682:Vena Cava, Inferior / Q000503:physiopathology / Q000601:surgery*; D014690:Venous Pressure; D055422:Venous Valves / Q000503:physiopathology / Q000637:transplantation*
keywords: Fontan circulation; hepatic venous hypertension; in vitro Fontan model; single ventricle; transcatheter valve