Directed intervention (coronary artery bypass surgery; intra-coronary stent placement) in the treatment of coronary artery disease is costly in patient morbidity, mortality and U.S. health care dollars. Methodologies that can improve the accuracy of application of these modalities deserve aggressive investigation. Magnetic Resonance Imaging (MRI) combined with radiofrequency tissue-tagging can non-invasively lay down transmural crosshatched grids in the myocardium that can be tracked throughout the cardiac cycle by MRI. Computer-based analysis techniques, developed in our laboratory, can track the grid intersections and generate regional point displacements and transmural 3D myocardial """"""""strain"""""""" maps. Strain is a normalized description of direction and degree of myocardial point movement. From these 3D strain maps we can determine the direction of principal strain vectors at every point throughout the left ventricle. We hypothesize, based on our preliminary data, that the direction of these vectors is very sensitive to the regionally-varying influence of coronary artery disease on contractile function and can introduce an unprecedented level of objective quantification and accurate regional localization of ischemia. These strain vectors will be utilized in a familiar testing algorithm: 1) baseline strain vector determinations are made, and 2) repeat determinations are made after low-dose Dobutamine. Areas with abnormal resting vectors are examined at low dose Dobutamine to see if they """"""""recruit,"""""""" suggesting viability and potential for benefit from coronary intervention. The hypotheses do not test this well established algorithm, but rather the capability of these techniques to bring accurate regional localization and objective quantification to the output data from the algorithm, and thus improve accuracy of application of directed coronary intervention.
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