"Atrial fibrillation (AF) prevalence is sky-rocketing, with AF affecting over 20 million Americans by 2030 unless more effective preventive strategies are developed. While obstructive sleep apnea (OSA) has been identified as a promising and treatable co-morbidity of AF, currently used scoring of OSA does not allow optimal treatment and prevention of AF, which was highlighted by the recent randomized trial. Our long-term objective is to develop an improved OSA scoring algorithm which is focused on the risk of AF, and which reflects the recently described patho-physiological mechanisms linking AF and OSA. In this pilot project we will compare novel and traditional variables of OSA-induced atrial arrhythmogenicity in patients with known history of AF, and compare these to control patients with OSA but without history of AF. To accomplish this, we will expand the traditional overnight polysomnography by measuring atrial conduction, arrhythmic triggers, autonomic imbalance, and blood pressure swings. From these pilot data we will identify promising variables for the novel OSA-AF severity score, which can then be further studied and refined in subsequent NIH funded prospective trials. Our multi-disciplinary team with long term interest in sleep-arrhythmia interactions, together with the promising preliminary data speak to the high feasibility of the proposed project."