Cardiac Electrophysiological Changes during High Intensity Focused Ultrasound Ablation.

High Intensity Focused Ultrasound;Optical Mapping;Infrared Imaging;Atrial Fibrillation;Parametric Ultrasound Imaging;Perfused Heart;Biomedical Engineering;Engineering;Biomedical Engineering

Wu, ZiqiChugh, Aman ;

University of Michigan

关键词: High Intensity Focused Ultrasound;    Optical Mapping;    Infrared Imaging;    Atrial Fibrillation;    Parametric Ultrasound Imaging;    Perfused Heart;    Biomedical Engineering;    Engineering;    Biomedical Engineering;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/100027/ziqiwu_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Atrial fibrillation (AF), the most common cardiac arrhythmia, is characterized by disorganized electrical activities that cause atrial quivering and uncoordinated contraction. AF significantly affects the quality of life for patients and increases the risk of stroke. Ultrasound ablation surgery has been proposed a decade ago as a treatment for AF. By focusing ultrasound energy at a narrow spot, rapid temperature rises along with tissue necrosis are generated. In this thesis, we investigated high-intensity focused ultrasound (HIFU), an ablation technology being used to eliminate arrhythmogenic foci for treatment of AF.During HIFU ablation, little is known regarding the detailed characteristics of cellular electrophysiological (EP) changes. The first part of the thesis aims to characterize EP changes during HIFU corresponding with temperature increases. Langendorff-perfused intact rabbit heart model stained with di-4-ANEPPS, a fluorescent dye sensitive to the membrane voltage changes, was used. Simultaneous optical mapping and infrared imaging were employed to measure epicardial EP and temperature during HIFU application. The results revealed the temperature-dependent spatiotemporal characteristics of HIFU-induced EP changes including changes of action potential (AP) amplitude, duration, and electrical activation. Temperature dosage criterion for generating irreversible tissue physical and AP changes were obtained. Intra-procedural imaging is important for guiding cardiac ablation for AF. However, it is difficult to obtain intra-procedural correlation of thermal lesion with AP changes in tissue transmural plane. The second part is to develop parametric ultrasound imaging techniques for transmural lesion and AP detection during ablation. Perfused canine ventricular wedge was used. Simultaneous optical mapping and high frequency ultrasound imaging of the same tissue trasnsmural plane were performed during HIFU. Tissue transmural EP changes were characterized and the AP changes were spatiotemporally correlated between optical and ultrasound images. The results show that parametric ultrasound imaging using cumulative extrema of ultrasound parameters (log-normal and Rayleigh) can detect HIFU lesions and surrounding AP amplitude changes.Overall, the information obtained from this thesis enhances our understanding of the EP mechanisms of HIFU ablation and can help promote the development of effective HIFU ablation strategies. Ultrasound parametric imaging provides a promising technique to identify lesion transmurality which is important in clinical ablations.