Jack D. Lemmon

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A computational fluid dynamics model for the analysis of the bileaflet mechanical heart valve closure process is presented. The objective of the study is to demonstrate the ability of the numerical model to simulate the leaflet motion during the closing phase in order to investigate the closure fluid dynamics and to evaluate the effect of alterations in the(More)
Ultrastructural changes during desiccation of the anhydrobiotic nematode Ditylenchus dipsaci were followed and quantified after preparation of material at different levels of hydration using freeze substitution techniques. Some shrinkage was caused by processing in the more hydrated specimens but the changes observed correspond to those observed in live(More)
BACKGROUND AND AIM OF THE STUDY This study examined the geometric distribution of chordae tendineae and their importance in compensating for papillary muscle (PM) displacement. METHODS Anatomic, chordal mechanics and hemodynamic measurements were performed with porcine mitral valves. For hemodynamic measurements, physiological pulsatile flow conditions(More)
A computational model that accounts for blood-tissue interaction under physiological flow conditions was developed and applied to a thin-walled model of the left heart. This model consisted of the left ventricle, left atrium, and pulmonary vein flow. The input functions for the model included the pulmonary vein driving pressure and time-dependent(More)
OBJECTIVE The aim of this study was to evaluate the hinge flow field characteristics of the Medtronic Advantage bileaflet valve and compare them with the flow fields of the St Jude Medical standard valve. The present study provides laser Doppler velocimetry results for the Advantage and St Jude Medical valves to make a direct comparison of the flow fields(More)
A numerical study was conducted to solve the three-dimensional Navier-Stokes equations for time-dependent flow in a compliant thin-walled, anatomically correct left ventricle during early systole. Model parameters were selected so that the simulation results could be compared to clinical data. The results produced endocardial wall motion which was(More)
BACKGROUND AND AIM OF THE STUDY Mitral annulus dilatation has been identified as an important factor in functional mitral regurgitation (FMR). However, the pathophysiologic interaction of annular dilatation and papillary muscle (PM) displacement in FMR, which occurs clinically in left ventricular (LV) dilatation, is still not well understood. It is(More)
BACKGROUND AND AIM OF THE STUDY The study aim was to characterize time-dependent flow fields and flow structures within the ADVANTAGE (ADV) and St. Jude Medical (SJM) prosthetic bileaflet mechanical heart valves. METHODS Three-dimensional unsteady computational fluid dynamic simulations were conducted in the aortic position for both valves. Flow boundary(More)
Aided by advancements in computer speed and modeling techniques, computational modeling of cardiac function has continued to develop over the past twenty years. The goal of the current study was to develop a computational model that provides blood-tissue interaction under physiologic flow conditions, and apply it to a thin-walled model of the left heart. To(More)
Systolic anterior motion of the mitral valve leaflets (SAM) is a disease of the left ventricle which results from an abnormal force balance on the mitral valve. The mechanism by which is initiated is poorly understood, and a complete understanding of this mechanism is required for effective treatment of SAM. There are currently two theories for the(More)