A Unique Case of Atrial Fibrillation Secondary to Squamous Cell Lung Carcinoma.

Atrial fibrillation (AF) is widely considered to be the most prevalent cardiac arrhythmia with an incidence of roughly 1%-2% in the United States alone. The incidence of AF has been known to increase with advancing age and thus presents a significant burden on healthcare systems across the globe. AF arises as a result of several mechanisms including structural changes that occur in the heart over time. Here, we present a case in which a 63-year-old male with no past medical history except heavy tobacco use presented to the emergency department complaining of shortness of breath. He also endorsed having palpations and a productive cough for several weeks prior to presenting to the emergency department. An EKG revealed AF with a rapid ventricular response. His chest x-ray revealed an irregular opacification of the left lung; however, a chest computed tomography unveiled a left hilar mass extending to the left upper lobe. The mass was causing obstruction of the left upper lobe and encasement of the left main pulmonary artery and left atrium. This case highlights a rare etiology of AF. While many causes of AF have been elucidated, including hypertension and valvular heart disease, a much lesser-known cause includes lung carcinoma resulting in a mass effect on the heart. Representing almost 19% of all cancer deaths, lung cancer is the leading cause of cancer death. Although lung cancer screenings are recommended for certain populations, the majority of lung cancer cases present at an advanced stage, limiting treatment options. Our patient presents a unique case involving a lung mass causing AF due to the mass effect on the left heart. Although the patient had other risk factors for AF including advanced age and cigarette smoking, we propose that due to the anatomical location of his lung mass, his AF was a consequence of the squamous cell carcinoma of the lung. Although the mortality for lung cancer remains high, new treatments, including pembrolizumab, have the potential to drastically alter the way these cancers are treated.