Purpose: Previous studies from our Laboratory demonstrated that quantitative measurements of myocardial fiber structure for individual hearts at specific transverse planes can be obtained from analyses of echocardiographic images. The objective of this study was to extend these echocardiographic‐based measurements to depict the myocardial fiber structure within the ventricular walls of the entire heart. Methods: A series of 2D apical echocardiographic images were acquired from 7 excised, intact, formalin‐fixed sheep hearts using a commercially available (GE Vivid) ultrasonic imaging system. Myocardial fiber orientations were determined from analyses of the measured transmural (radial) ultrasonic backscatter profiles within the ventricular walls in conjunction with a previously determined relationship between the observed backscatter level and the angle of insonification relative to myocardial fiber orientation. These data were assembled to produce a fiber orientation image map of the entire left and right ventricular walls of each heart. In addition, 3D volumetric, apical echocardiographic images were acquired from a subset of the excised hearts for comparison. Results: Image maps depicting myocardial fiber structure throughout the ventricular walls appear consistent with the known fiber structure of the heart. Images demonstrate left‐ventricular mid‐myocardial fibers oriented within the short axis plane and gradually becoming more longitudinally oriented toward the epicardial and endocardial surfaces. Preliminary data from 3D volumetric, apical echocardiographic images suggest similar results. Conclusion: These results demonstrate that measurements of myocardial fiber structure throughout the entire heart can be successfully derived from analyses of echocardiographic images. Further development of this method may provide a method for mapping the myocardial fiber orientation in individual patients over the heart cycle and provide a means for assessing potentially altered fiber structure associated with congenital and acquired heart diseases. [NIH R01 HL040302]; Funded, in part, by NIH R01 HL040302; Dr. Kirk D. Wallace is an employee of GE Global Research.
|Number of pages||1|
|State||Published - Jun 2013|