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Development of Cardiac Atrial Kick Shear Wave Elastography to Assess Myocardial Stiffness
Increased myocardial stiffness, which is characteristic of many cardiovascular diseases, leads to a loss of diastolic function and is a cause of diastolic heart failure. Current methods to estimate myocardial stiffness rely on pressure-volume relationships derived from invasive cardiac catheter measurements. Noninvasive methods to estimate myocardial stiffness include ultrasound-based and magnetic resonance-based shear wave elastography, where the stiffness of the tissue is related to the propagation speed of a shear wave. Currently, ultrasound-based cardiac shear wave elastography includes acoustic radiation force based methods; however, the in vivo generation and detection of the shear waves in myocardium is significantly degraded due to limited acoustic radiation force penetration and clutter noise introduced from the chest wall. A similar degradation of shear waves occurs in cardiac magnetic resonance elastography because of the external source used for shear wave generation. Consistently successful cardiac shear wave elastography is limited to patients with a thin chest wall and low body mass index. To meet the needs of the patients suffering from diastolic heart failure, the long-term goal of this research is to develop a cardiac shear wave elastography technique where the shear wave is generated within the heart by the mechanical stimulus of the late diastolic atrial kick. The amplitude of this wave is at least one order of magnitude higher than acoustic radiation force induced shear waves and thus more easily visualized, having a higher chance of detection in a broader patient population. This dissertation introduces a method for shear wave speed estimation in shear wave elastography and compares it to conventional methods. A method termed cardiac atrial kick shear wave elastography is introduced to measure the atrial kick shear wave speed. A pilot study was performed using this method which measured the atrial kick shear wave speed and compared it to common measures of cardiac health taken at the clinic and in conventional echocardiogram reports. Results suggest that cardiac atrial kick shear wave elastography is a promising tool that can be used for assessment of diastolic function and myocardial stiffness.
Biomedical engineering|Electrical engineering
Engel, Aaron J, "Development of Cardiac Atrial Kick Shear Wave Elastography to Assess Myocardial Stiffness" (2017). ETD collection for University of Nebraska - Lincoln. AAI10641495.