published_or_final_version / Medicine / Master / Master of Philosophy

Patients with atrial fibrillation (AF) require modification of ectopic electrical activity to avoid potentially fatal health complications. Catheter ablation therapy is a minimally invasive procedure to create tissue necrosis, called lesion, in areas of abnormal electrical activity. However, significant proportion of patients require repeat treatment from AF recurrences in part by electrical reconnection from incomplete lesions and conduction recovery. Current therapeutic approaches are limited by reliable methods to assess AF structural substrates and validate lesion sufficiency during procedures. In recent years, development of near-infrared optical spectroscopy has provided a non-invasive method to evaluate biological tissue. Near infrared spectroscopy (NIRS) is an optical technique that enables direct characterization of pathological tissue based on the absorption of major chromophores and light scattering. In this thesis, we explore the use of near-infrared optical spectroscopy to identify AF substrates and quantify lesion formation to improve treatment efficacy. First, we developed a near-infrared multispectral imaging system and present a model to assess lesion adequacy by direct visualization of cardiac lesions through an endoscope-integrated probe. Then, a custom single fiber integrated radiofrequency (RF) ablation catheter was fabricated to track irrigated lesion progression real-time on ex vivo swine hearts. A machine learning model was introduced to predict lesion size and transmurality. Additionally, we assess the feasibility of near-infrared spectroscopy by fabricating a NIRS-integrated open-irrigation RF ablation catheter and an algorithm to assess lesion dimensions based on key features derived from NIRS measurements. Using this model, we demonstrate real-time tracking of irrigated lesion delivery in both ex vivo and in vivo swine model. Lastly, we show left atrial endocardial mapping with NIRS-integrated RF mapping catheter to assess AF structural substrates. We present a classification algorithm for important AF structural substrates, such as pulmonary vein sleeve, normal myocardium, ablated tissue, and fibrosis, and a regression model to validate lesion adequacy. A near-infrared spectroscopy-based techniques to localize structural complexities and validate lesion sufficiency at the catheter tip could enhance the understanding of underlying AF substrates and improve treatment efficacy.

Atrial fibrillation is a common arrhythmia encountered in the emergency department. In the United States, newly diagnosed cases of atrial fibrillation is projected to be 2.6 million cases in 2030 and the annual prevalence of atrial fibrillation is expected to be 12.1 million in 2030 (Colilla et al., 2013). Patients may present to the emergency department for treatment of atrial fibrillation with a variety of symptoms and therefore makes diagnosing atrial fibrillation based on symptomatology challenging for the clinician. The primary goal of this Doctor of Nursing Practice (DNP) project is to describe symptoms of atrial fibrillation in patients that seek medical treatment in the emergency department. Methods: This descriptive study contains secondary analysis of existing data derived from structured interviews that took place at two academic medical centers. This analysis included 74 patients that presented to the emergency department with symptoms suspected of acute coronary syndrome and were later diagnosed with atrial fibrillation. Descriptive statistics were used to synthesize data, while inferential statistics (bivariate tests) were used to compare symptoms between the age groups. Results: The mean age of subjects was 70 + 13 years, ranging 31 to 92 years. The majority of subjects were men (75.7%) and whites (90.5%). The most common symptoms reported by study subjects included chest discomfort (n = 50; 67.6%), followed by generalized weakness (n = 39; 52.7%) and shortness of breath (n = 39; 52.7%), and palpitations/ funny beating of the heart (n = 36; 48.6%) and unusual fatigue/ tiredness (n = 36; 48.6%). Sweating was the only symptom that was statistically significant in the younger adult group than in the older adult age group. Conclusion: The symptoms identified in this DNP project can be used to aid in identifying patients that present to the emergency with symptomatic atrial fibrillation. Further efforts for the assessment of atrial fibrillation should focus on the dissemination of common although nonspecific symptoms to facilitate the inclusion of atrial fibrillation as part of the differential diagnosis.