An Uncommon Case of Atrial Fibrillation due to a Lung Mass Invasion of the Left Atrial Cavity.

Atrial fibrillation remains one of the most common conditions that clinical physicians encounter on a daily basis in the inpatient setting. This arrhythmia brings with it numerous complications if not treated properly and leads to intensive analysis of its primary etiology which is unique to every patient. In this case, we present a previously asymptomatic individual who presented to the hospital with respiratory complaints and was found to have a large lung mass, consistent with neuroendocrine lung cancer with direct compression of the left atrium leading to new-onset atrial fibrillation.