Compression of the Left Brachiocephalic Vein by a Type II Right Aortic Arch: A Rare Vascular Anomaly With Unique Clinical Presentation

Right-sided aortic arch (RAA) is an uncommon anatomical variation of the thoracic vasculature, occurring in approximately 0.1% of adults. In nearly half of these instances, the left subclavian artery follows an abnormal course. The left subclavian artery typically emerges from a tapered dilation at its origin from the aorta, referred to as Kommerell's diverticulum (KD). Based on available literature, only a few cases have been documented. We describe a 62-year-old female patient who presented with a painless chest bump persisting for four weeks. She reported no symptoms such as cough, shortness of breath, fainting, or difficulty swallowing. Upon chest inspection, the middle of the chest exhibited a mild protrusion. Her vital signs were stable, and both pulmonary and cardiovascular examinations were normal. After an initial workup, a CT angiogram of the chest was performed and revealed the presence of a RAA compressing the left brachiocephalic vein (LBCV ) in addition to an aberrant left subclavian artery (ALSA). In adults, right-sided aortic arch with an aberrant left subclavian artery originating from KD is a rare but typically silent anomaly. However, it can become clinically significant if complications arise, such as severe aneurysmal changes or compression of nearby mediastinal structures. Patients may then present with chest pain or dyspnea, coughing, and swallowing issues. In this case, the anomaly led to compression of the left brachiocephalic vein, resulting in its dilation and visible protrusion. Although standardized treatment guidelines are lacking, it is important to educate patients about the nature and potential risks of this condition. For those without symptoms, regular monitoring may be appropriate, with surgical intervention considered if complications emerge.