Publications (38) View all
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Article: Trabeculae carneae as models of the ventricular walls: implications for the delivery of oxygen.
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ABSTRACT: Trabeculae carneae are the smallest naturally arising collections of linearly arranged myocytes in the heart. They are the preparation of choice for studies of function of intact myocardium in vitro. In vivo, trabeculae are unique in receiving oxygen from two independent sources: the coronary circulation and the surrounding ventricular blood. Because oxygen partial pressure (PO(2)) in the coronary arterioles is identical in specimens from both ventricles, whereas that of ventricular blood is 2.5-fold higher in the left ventricle than in the right ventricle, trabeculae represent a "natural laboratory" in which to examine the influence of "extravascular" PO(2) on the extent of capillarization of myocardial tissue. We exploit this advantage to test four hypotheses. (1) In trabeculae from either ventricle, a peripheral annulus of cells is devoid of capillaries. (2) Hence, sufficiently small trabeculae from either ventricle are totally devoid of capillaries. (3) The capillary-to-myocyte ratios in specimens from either ventricle are identical to those of their respective walls. (4) Capillary-to-myocyte ratios are comparable in specimens from either ventricle, reflecting equivalent energy demands in vivo, driven by identical contractile frequencies and comparable wall stresses. We applied confocal fluorescent imaging to trabeculae in cross section, subsequently using semi-automated segmentation techniques to distinguish capillaries from myocytes. We quantified the capillary-to-myocyte ratios of trabeculae from both ventricles and compared them to those determined for the ventricular free walls and septum. Quantitative interpretation was furthered by mathematical modeling, using both the classical solution to the diffusion equation for elliptical cross sections, and a novel approach applicable to cross sections of arbitrary shape containing arbitrary disposition of capillaries and non-respiring collagen cords.The Journal of General Physiology 09/2009; 134(4):339-50. · 3.84 Impact Factor -
Article: Modeling Cardiac Electrical Activity at the Cell and Tissue Levels
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ABSTRACT: Significant tissue structures exist in cardiac ventricular tissue, which are of supracellular dimension. It is hypothesized that these tissue structures contribute to the discontinuous spread of electrical activation, may contribute to arrhythmogenesis, and also provide a substrate for effective cardioversion. However, the influences of these mesoscale tissue structures in intact ventricular tissue are difficult to understand solely on the basis of experimental measurement. Current measurement technology is able to record at both the macroscale tissue level and the microscale cellular or subcellular level, but to date it has not been possible to obtain large volume, direct measurements at the mesoscales. To bridge this scale gap in experimental measurements, we use tissue-specific structure and mathematical modeling. Our models, which can incorporate ion channel models at the cell level into the reaction–diffusion equations at the tissue level, have enabled us to consider key hypotheses regarding discontinuous activation.Annals of the New York Academy of Sciences 11/2006; 1080(1):334 - 347. · 3.15 Impact Factor -
Conference Proceeding: Automated Extended Volume Imaging of Tissue using Confocal and Optical Microscopy
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ABSTRACT: Conventional histologic techniques cannot readily be used for 3D reconstruction of large tissue volumes. We have developed an imaging rig which supports both confocal and light microscopy, and utilizes a surface imaging approach to serially image embedded tissue blocks while maintaining alignment and registration of the image seriesEngineering in Medicine and Biology Society, 2006. EMBS '06. 28th Annual International Conference of the IEEE; 10/2006 -
Conference Proceeding: Construction of Patient Specific Geometries Suitable for the Inverse Problem of Electrocardiography
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ABSTRACT: The ability to accurately construct a geometric representation of the heart and torso is a critical component for electrocardiographic inverse algorithms. Typically geometric models have been constructed using data acquired from imaging modalities such as MRI and CT. We propose a system where the torso surface geometry is obtained using a laser scanning device and the heart geometry is obtained using three-dimensional ultrasoundEngineering in Medicine and Biology Society, 2005. IEEE-EMBS 2005. 27th Annual International Conference of the; 02/2006 -
Article: Experiment-specific models of ventricular electrical activation: construction and application.
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ABSTRACT: Experimental intramural recordings of electrical activity at high resolution have been made in the in-vivo pig LV free wall. To analyze features of these recordings experiment-specific 3D computer models of tissue structures and electrical behavior around the recording sites were constructed. The construction of the models used novel tissue image registration, correction and feature extraction methods. Appropriate model conductivity parameters were deduced from measurements and used to replicate features of experimental recordings.Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 02/2008; 2008:137-40.
