No abstract

Regional myocardial function assessment is essential for diagnosis and evaluation of heart disease. The purpose of this study was to enhance the spatial resolution of a speckle tracking echocardiography approach and enable layer-specific analysis of the myocardium. Following validation with software-implemented and mechanical phantoms versus imposed values, short-axis cines were obtained from 50 rats. The cines were post-processed by a speckle tracking commercial program, and the myocardial velocities were processed by a three-dimensional wavelet de-noising program, instead of the built-in smoothing process of the commercial program. Software-implemented phantom measurements yielded rotation errors of 7.5%, 2.9%, and 3.4%, for inner, middle, and outer layers, respectively. Analysis of a shrinking/expanding mechanical phantom yielded strain errors of 3%, 5%, and 7% for the three layers. Bland-Altman analysis showed agreement between the commercial and enhanced programs. Thus, layer-specific analysis is feasible while using echocardiography even on small animals such as rats.

Background: Myocardial infarction (MI) is known to progress from the inner layers towards the epicardium. Since it is important to detect MI early, to prevent a negative remodeling process of the left ventricle (LV), the hypothesis of this study was that evaluation of layer-specific strains is feasible, and it will enable differentiation between subjects with large MI, small MI and normal LV. Methods:In this study a commercial speckle tracking echocardiography (STE) program was modified to measure the strains at three myocardial layers instead of for the total-wall-thickness. After a validation process by using software implemented phantoms, the commercial and modified programs were applied to echocardiography of 54 subjects. Results:The validation study results for 972 segments showed an agreement between the endocardial strains, manually measured by the commercial program, and automatically measured by the modified program. Finally, the algorithm was applied to scans of 15 normal subjects, 9 patients with small MI and to 6 patients with large MI. The results show that the strain elevated from the endocardium towards the epicardium for the normal and small MI groups, but not for the large MI group. Conclusions:In conclusion, the layer-specific STE method allows accurate analysis of the transmural variations of the strains.