eng Science and Education Publishing American Journal of Medical Case Reports 2374-216X 2020-12-18 9 2 125 130 10.12691/ajmcr-9-2-7 AJMCR2021927 article Krunal H Patel 1 Vaibhavi Uppin 2 Harshith Chandrakumar 2 Yuvraj Singh Chowdhury 2 Jonathan Ramalho 2 Basil Elamir 2 Loius Sacicciioli 2 Harjinder Gill 2 Sarah Hennis 2 Samy I. McFarlane smcfarlane@downstate.edu 2 Department of Internal Medicine, State University of New York, Downstate Health Science University, Brooklyn, NY, USA - 11203 Division of Cardiovascular Disease, State University of New York, Downstate Health Science University, Brooklyn, NY, USA - 11203 Although uncommon, aortic dissection can be rapidly fatal with a 20% out-of-hospital mortality which increases at a rate of 1 to 3% every hour [1]. An expeditious diagnosis of acute aortic dissection is therefore imperative. One of the most advantageous diagnostic modalities utilized in the setting of acute aortic dissection is a transesophageal echocardiogram (TEE). In an acute setting, TEE is preferred because of its ability to provide a timely and definitive diagnosis [2]. Despite its diagnostic convenience, clinicians must be aware that there are several entities that may mimic aortic dissection. One of these entities includes a dilated accessory hemiazygos vein. In this report, we present a case of a 66-year-old woman who was found to have a possible Stanford type B dissection in the descending thoracic aorta on a TEE exam in the context of work up prior to an elective electrophysiology study and ablation for paroxysmal atrial fibrillation. CT angiography, however, revealed a dilated accessory hemiazygos vein, a rare congenital vascular anomaly that could potentially mimic aortic dissection leading to misdiagnosis and potentially unnecessary interventions. http://pubs.sciepub.com/ajmcr/9/2/7/ajmcr-9-2-7.pdf aortic dissection transesophageal echocardiogram hemiazygos vein brachiocephalic vein congenital vascular anomaly