Weekly Seminar: Spring 2013
Speaker: Dr. Sándor Kovács (Washington University in St. Louis)
Title: "How Your Heart Works When It Fills: An Engineering Perspective"
Date: Friday, April 12, 2013
Time: 11:00 a.m.
Location: Gilman Hall 50 (Marjorie M. Fisher Room)
The two engineering principles that govern the diastolic (filling) phase of all human hearts are "constant volume pump" and "suction pump."
The approx 850 ml volume of the pericardial sac decreases by only approx 40 ml by end systole. This requires that atrial-ventricular volumes simultaneously reciprocate and it underscores the pressure pump (systolic) and volume pump (diastolic) roles of the coordinated function of the chambers. Of the 4 heart chambers ONLY the left ventricle actually serves as a (systolic) pressure pump. When the normal left ventricle initiates filing at mitral valve opening, it generates only a small (4mmHg) maximum atrio- ventricular pressure gradient (LVP< LAP) while LV pressure continues to decrease for about 100 msec while LV volume increases (dP/dV< 0). Because the chamber recoils faster than it can fill it is a suction (volume) pump. The purpose of diastole is to fill the chamber (mass transfer in two phases) in the fraction of a second available in order to maintain cardiac output. Suction initated filling allows the chamber to return to its equilibrium (diastatic) volume. The streamlines entering through the 5cm2 mitral valve rapidly form an asymmetric toroidal vortex whose formation time has been shown to depend on LV chamber parameters of stiffness, relaxation and load. Recent Lagrangian coherent structure (LCS) analysis of MRI data of vortex ring growth in the LV reveals nature's elegant fluid mechanics based solution to the diastolic mass transfer problem. The intraventricular vortex also "rinses" the trabeculated inner surface of the heart thereby preventing formation of blood clots and facilitates mitral leaflet coaptation to minimize mitral valve regurgitation.
Sándor J. Kovács received his Ph.D. in Physics at Caltech, CA and then went on to receive his M.D. in Medicine at the University of Miami, FL. After an internship and residency at Barnes Hospital; Kovács became an instructor in medicine in 1985, served as director of the cardiac catheterization laboratory at the St Louis VA Medical Center (1985-1990) advancing through the ranks to professor of medicine, with also appointments in physiology, biomedical engineering, and physics, in 2007.
His research is in the Cardiovascular Biophysics Laboratory (CBL) which focuses on a systems physiologic perspective of cardiac function and dysfunction. The primary conceptual approach is theoretical and mathematical with validation using in-vivo human cardiovascular data. Theoretical work involves noninvasive, quantitative diastolic function assessment and fully characterization of the role of the heart as a suction pump. Particular emphasis is placed on predicting 'new' physiology from first principles, the testing of physiologic hypotheses amenable to in-vivo verification via invasive and noninvasive means. In addition, suitable statistical methods and related analytical and numeric methods based tools are utilized in the Cardiovascular Biophysics Laboratory.
Kovács received the Sjöstrand Medal in Physiology from the Swedish Society of Clinical Physiology and Medicine in 2007. He was elected President of the Cardiovascular System Dynamics Society (CSDS) in 2006 and served until 2008. He is a recipient of the Öcsi Bácsi Award of Caltech's TAPIR Group.
Speaker: Prof. Elie Bou-Zeid (Princeton University)
Title: "New insights into the dynamics of the stably-stratified Ekman boundary layer from direct and large-eddy simulations"
Date: Friday, September 5, 2014
Time: 11:00 a.m.
Location: Gilman Hall 132
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