M.Sc Thesis

M.Sc StudentShlomo Liron
SubjectDetection of Viable Tissue in a Rat Model of Small
Sub-Endocardium Infarct Utilizing Speakle
Tracking Echocardiography
DepartmentDepartment of Biomedical Engineering
Full Thesis textFull thesis text - English Version


Immediately after the onset of myocardial ischemia the affected area, which is termed Area at Risk, suffers from contractile dysfunction. The area at risk can be divided into two regions: infarcted and stunned, both display contractile dysfunction but only the latter may recuperate. The size and shape of the infarcted tissue determines the effect it has on global parameters such as EF and local parameters such as circumferential and longitudinal strains. It is hard to detect and localize non-Transmural (not affecting the whole thickness of the myocardial wall) infarcts at presentation regardless of the diagnosis method. It has been shown by Picano et al. 19961 that stress echocardiography can help distinguish between stunned (but viable) and infarcted tissue. OBJECTIVES: Utilize speckle tracking echocardiography analysis of short-axis view to determine what parameters may allow differentiating between necrotic and stunned tissue, in aforementioned case. METHODS: Animal Model: infarcts were induced in 11 male Sprague Dawley rats (weight 300 ± 25 g), by performing an ischemia-reperfusion preconditioning followed by a 30 minutes ligation of a coronary artery (LAD). The resulting ischemia was measured by histopathology (H&E, MTC). Echocardiography: Each rat underwent four echocardiography tests using the 10S probe with Vivid-i (GE Healthcare): Baseline; Rest and Stress (day 1); Rest (day 7). The short-axis view of the apical level was divided into three segments: Proximal; Medial; Distal. Four indices were computed by analyzing cines using transmural 2D Speckle Tracking Echocardiography. RESULTS: At rest, Peak Systolic Strain identified dysfunction at proximal and medial regions when compared to contractility at the distal region; no injury was identified during stress. This result suggests small infarcts - in accordance with the histology analysis. However, further tests showed poor repeatability performance, which may be the cause of the less satisfactory attributes demonstrated by the other three parameters. CONCLUSION: The analysis used here demonstrates that utilizing short-axis STE with dobutamine for detection of dysfunctional tissue is feasible. The animal model which was used in this work indeed produces small infarcts. The main issue that arose was tracking quality that caused a large variance in results which were expected to be similar; this can be improved by using automatic detection of the endocardium instead of the manual placement of tracking points, as was executed here.