الفهرس 
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Abstract
HF is the end stage of all diseases of the heart and is a major cause of morbidity and mortality. Although heart failure may result from disorders of the pericardium, myocardium, endocardium or valve structures, or the great vessels of the heart, or from rhythm disturbances, it is usually discussed primarily in terms of myocardial dysfunction (Levy D, Kenchaiah S, Larson MG et al, 2002 Electromechanical coupling occurs at multiple anatomic levels: within) atria, between atria and ventricles, between ventricles, and especially within the left ventricle (Michael O. Sweeney and Frits W. Prinzen,2008) A failing electrical conduction system can cause delays in timing of mechanical activation of the myocytes, which also changes the myocardial contraction pattern, which will eventually be accompanied by loss of pump function (Grines CL, Bashore TM et al, 1989 Echocardiography has been the most widely studied imaging modality to identify candidates for CRT, for primary (prospective) optimization immediately after CRT initiation as well as secondary optimization in non-responders (Lisa M. Fleming. et al,2011). STE is based on an analysis of the spatial dislocation of speckles ,defined as spots generated by the interaction between the ultrasound beam and myocardial fibers, on routine2-dimensional sonograms. (Götte et al., 2011 The limitations of medical therapy for heart failure have generated great interest in non-pharmacological treatments. The most efficacious non