title: Aortic Regurgitation Generates a Kinematic Obstruction Which Hinders Left Ventricular Filling.
abstract: An incompetent aortic valve (AV) results in aortic regurgitation (AR), where retrograde flow of blood into the left ventricle (LV) is observed. In this work, we parametrically characterized the detailed changes in intra-ventricular flow during diastole as a result of AR in a physiological in vitro left-heart simulator (LHS). The loss of energy within the LV as the level of AR increased was also assessed. The validated LHS consisted of an optically-clear, flexible wall LV and a modular AV holder. Two-component, planar, digital particle image velocimetry was used to visualize and quantify intra-ventricular flow. A large coherent vortical structure which engulfed the whole LV was observed under control conditions. In the cases with AR, the regurgitant jet was observed to generate a "kinematic obstruction" between the mitral valve and the LV apex, preventing the trans-mitral jet from generating a coherent vortical structure. The regurgitant jet was also observed to impinge on the inferolateral wall of the LV. Energy dissipation rate (EDR) for no, trace, mild, and moderate AR were found to be 1.15, 2.26, 3.56, and 5.99 W/m3, respectively. This study has, for the first time, performed an in vitro characterization of intra-ventricular flow in the presence of AR. Mechanistically, the formation of a "kinematic obstruction" appears to be the cause of the increased EDR (a metric quantifiable in vivo) during AR. EDR increases non-linearly with AR fraction and could potentially be used as a metric to grade severity of AR and develop clinical interventional timing strategies for patients.
authors.affiliation: School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, USA.|Exponent Failure Analysis Associates, 3440 Market Street, Suite 600, Philadelphia, PA, USA.
authors.forename: Ikechukwu
authors.initials: I
authors.lastname: Okafor
authors.affiliation: Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Technology Enterprise Park, 387 Technology Circle, Suite 200, Atlanta, GA, 30313-2412, USA.|Department of Aerospace Engineering, Auburn University, 1301 Shelby Center, Auburn, AL, USA.
authors.forename: Vrishank
authors.initials: V
authors.lastname: Raghav
authors.affiliation: Division of Cardiology, Emory University Hospital, Atlanta, GA, USA.
authors.forename: Jose F
authors.initials: JF
authors.lastname: Condado
authors.affiliation: Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA.
authors.forename: Prem A
authors.initials: PA
authors.lastname: Midha
authors.affiliation: Division of Cardiology, Emory University Hospital, Atlanta, GA, USA.|Atlanta Veterans Affairs Medical Center, Decatur, GA, USA.
authors.forename: Gautam
authors.initials: G
authors.lastname: Kumar
authors.affiliation: School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, USA. ajit.yoganathan@bme.gatech.edu.|Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Technology Enterprise Park, 387 Technology Circle, Suite 200, Atlanta, GA, 30313-2412, USA. ajit.yoganathan@bme.gatech.edu.
authors.forename: Ajit P
authors.initials: AP
authors.lastname: Yoganathan
mesh_terms: D000818:Animals; D001022:Aortic Valve Insufficiency / Q000503:physiopathology*; D001696:Biomechanical Phenomena; D001783:Blood Flow Velocity; D006352:Heart Ventricles / Q000503:physiopathology*; D008955:Models, Cardiovascular; D013552:Swine; D014694:Ventricular Outflow Obstruction / Q000503:physiopathology*
keywords: Aortic regurgitation; Aortic valve; Energy dissipation; Left ventricle filling; Vortex flow