Browsing by Subject "Electrocardiography"

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    The Non-Invasive Application of Electrocardiography in the Optimization of Cardiac Resynchronization Therapy
    (2020-08) Harbin, Michelle
    Cardiac resynchronization therapy (CRT) is intended to reverse electrical dyssynchrony and improve systolic function in heart failure patients. However, roughly 30% of recipients do not clinically or echocardiography benefit, despite advancements with implant techniques and pacing technology, and are considered to be non-responders (Auricchio & Prinzen, 2011). Suboptimal postoperative device programming of the interventricular and atrioventricular delays, and the left ventricular (LV) pacing vector in quadripolar leads, is thought to be a prevailing cause of this persistent non-response (Mullens et al., 2009). Device optimization of pacing configurations is highly underutilized, and research has yet to establish a standardized, patient-specific methodology that can be routinely used in outpatient heart failure clinics (Gras, Gupta, Boulogne, Guzzo, & Abraham, 2009; N. Varma et al., 2019). The use of electrocardiography in device optimization is supported by the notion that synchronous ventricular electrical activation is a requisite for adequate systolic and diastolic function (Nguyen, Verzaal, van Nieuwenhoven, Vernooy, & Prinzen, 2018). Electrocardiography has furthermore shown promise in routine CRT device optimization owning to its non-invasive, inexpensive, and practical attributes. QRS duration shortening during the paced rhythm, as well as metrics of wavefront fusion and cancellation, on 12-lead electrocardiograms have been reported to correlate with subsequent LV reverse remodeling (Gage et al., 2018; Sweeney et al., 2014; Sweeney et al., 2010). Innovations in technology allow for the application of multiple unipolar electrodes placed over the upper anterior and posterior torso (Bank et al., 2018; Johnson et al., 2017; Rickard et al., 2020). The intent of this technology, as depicted in its ability to simultaneously acquire ventricular activation from both anterior and posterior surfaces, is to provide a better assessment of electrical dyssynchrony relative to that of a 12-lead electrocardiogram. Previous reports have shown that this technology can accurately, non-invasively, and efficiently measure electrical heterogeneity in patients with CRT devices (Gage et al., 2017). The purpose of this dissertation is to use this technology to: (1) quantify how a device-based pacing algorithm improves electrical resynchronization, and (2) evaluate the therapeutic window on the corresponding potential of electrical resynchronization during left ventricular unipolar pacing.
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    Noninvasive imaging of three-dimensional ventricular electrical activity
    (2012-08) Han, Chengzong
    Noninvasive imaging of cardiac electrical activity is of great importance and can facilitate basic cardiovascular research and clinical diagnosis and management of various malignant cardiac arrhythmias. This dissertation research is aimed to investigate a novel physical-model-based 3-dimensional cardiac electrical imaging (3DCEI) approach. The 3DCEI approach is developed by mathematically combining high-density body surface electrocardiograms (ECGs) with the anatomical information. Computer simulation study and animal experiments were conducted to rigorously evaluate the performance of 3DCEI. The simulation results demonstrate that 3DCEI can localize the origin of activation and image the activation sequence throughout the three-dimensional ventricular myocardium. The performance of 3DCEI was also experimentally and rigorously evaluated through well-controlled animal validation studies in both the small animal model (rabbit) and large animal model (canine), with the aid of simultaneous intramural recordings from intra-cardiac mapping using plunge-needle electrodes inserted in the ventricular myocardium. The clinical relevance of 3DCEI was further demonstrated by investigating 3DCEI in cardiac arrhythmias from animal models with experimentally-induced cardiovascular diseases. The consistent agreement between the non-invasively imaged activation sequences and its directly measured counterparts in both the rabbit heart and canine heart implies that 3DCEI is feasible in reconstructing the spatial patterns of ventricular activation sequences, localizing the arrhythmogenic foci, and imaging dynamically changing arrhythmia on a beat-to-beat basis. The promising results presented in this dissertation study suggest that this cardiac electrical imaging approach may provide an important alternative for non-invasively imaging cardiac electrical activity throughout ventricular myocardium and may potentially become an important tool to facilitate clinical diagnosis and treatments of malignant ventricular arrhythmias.