Cardiac assessment mechanics: 1 Left ventricular mechanomyocardiography,a new approach to the detection of diseased myocardial elements and states |
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Authors: | D N Ghista G Ray H Sandler |
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Institution: | (1) Department of Mechanical Engineering-Engineering Mechanics, Michigan Technological University, 49931 Houghton, Michigan, USA;(2) Mechanical Engineering Department, Southern University, 70813 Baton Rouge, Louisiana, USA;(3) Biomedical Research Division, NASA, Ames Research Centre, 94035 Moffett Field, California, USA |
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Abstract: | The inadequacies of currently employed methods for assessment of cardiac mechanics are discussed, and the need for development
of more intrinsic assessment parameters is emphasised. To this end, a new technique is presented to enable determination of
regional mechanical constitutive properties of the myocardium during diastole; this technique has been originally named left-ventricular
mechanomyocardiography (or l.v.-m.m.c.g.). The data required for implementation of the techniques consist of left-ventricular
sequential dynamic geometry and associated recorded chamber pressure. The method entails matching of the inner-boundary deformations
of the instantaneous finite-element model of the left ventricle (which is loaded by the recorded instantaneous incremental
pressure) with the actual instantaneous endocardial deformations (as derived from either cineangiocardiography or 2-dimensional
echocardiography), to determine the regional distribution of the Young's modulus Ene and the incremental stresses Δσne (and hence the total stress σne=∑nΔσne) of the myocardial elements. The mechanical constitutive properties of the myocardial elements can be then characterised
by the constitutive relation Ene=a+bσ. The constitutive parameters a and b have typical ranges for normal and pathological (ischaemic and infarcted) myocardial
elements and hence can be employed to distinguish diseased elements. The values of a and b are calculated for normal and pathological
subjects and their normal and pathological ranges are presented. |
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