title: Atrial systole enhances intraventricular filling flow propagation during increasing heart rate.
abstract: Diastolic fluid dynamics in the left ventricle (LV) has been examined in multiple clinical studies for understanding cardiac function in healthy humans and developing diagnostic measures in disease conditions. The question of how intraventricular filling vortex flow pattern is affected by increasing heart rate (HR) is still unanswered. Previous studies on healthy subjects have shown a correlation between increasing HR and diminished E/A ratio of transmitral peak velocities during early filling (E-wave) to atrial systole (A-wave). We hypothesize that with increasing HR under constant E/A ratio, E-wave contribution to intraventricular vortex propagation is diminished. A physiologic in vitro flow phantom consisting of a LV physical model was used for this study. HR was varied across 70, 100 and 120 beats per minute (bpm) with E/A of 1.1-1.2. Intraventricular flow patterns were characterized using 2D particle image velocimetry measured across three parallel longitudinal (apical-basal) planes in the LV. A pair of counter-rotating vortices was observed during E-wave across all HRs. With increasing HR, diminished vortex propagation occurred during E-wave and atrial systole was found to amplify secondary vorticity production. The diastolic time point where peak vortex circulation occurred was delayed with increasing HR, with peak circulation for 120bpm occurring as late as 90% into diastole near the end of A-wave. The role of atrial systole is elevated for higher HR due to the limited time available for filling. Our baseline findings and analysis approach can be applied to studies of clinical conditions where impaired exercise tolerance is observed.
authors.affiliation: School of Mechanical and Aerospace Engineering, Oklahoma State University, 218 Engineering North, Stillwater, OK 74078, USA; Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology & Emory University, 315 Ferst Drive, Atlanta, GA 30332, USA. Electronic address: askrish@okstate.edu.
authors.forename: Arvind
authors.initials: A
authors.lastname: Santhanakrishnan
authors.affiliation: School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA. Electronic address: iokafor3@gatech.edu.
authors.forename: Ikechukwu
authors.initials: I
authors.lastname: Okafor
authors.affiliation: Division of Cardiology, Emory University School of Medicine, Atlanta, GA 30322, USA. Electronic address: gautam.kumar@emory.edu.
authors.forename: Gautam
authors.initials: G
authors.lastname: Kumar
authors.affiliation: School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA; Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology & Emory University, 315 Ferst Drive, Atlanta, GA 30332, USA. Electronic address: ajit.yoganathan@bme.gatech.edu.
authors.forename: Ajit P
authors.initials: AP
authors.lastname: Yoganathan
mesh_terms: D016275:Atrial Function; D006339:Heart Rate / Q000502:physiology*; D006439:Hemodynamics; D006801:Humans; D008955:Models, Cardiovascular; D013599:Systole / Q000502:physiology*; D016277:Ventricular Function, Left
keywords: Atrial systole; Flow phantom; Heart rate; Intraventricular flow; Left ventricle