SESSION TITLE: Cardiovascular Disease SESSION TYPE: Med Student/Res Case Report PRESENTED ON: 10/09/2018 07:30 AM - 08:30 AM INTRODUCTION: Stridor is usually caused by turbulent flow in the upper airways. We present a case of stridor due to a dissecting aortic aneurysm in a patient with an anomalous aortic arch. CASE PRESENTATION: A 65 year-old female smoker presented following a fall with hypertensive emergency and right cerebellar hematoma, believed to be due to uncontrolled hypertension. Initial evaluation showed somnolence and confusion without focal neurologic deficit. CT chest, abdomen and pelvis was performed to rule out a primary cancer with brain metastases as a cause of cerebellar hematoma. Chest CT incidentally showed a subacute type B aortic dissection extending down to the aortic bifurcation with involvement of both renal arteries.During hospitalization, the patient developed inspiratory stridor and expiratory wheezing worse with laying supine or on the right side. The stridor almost completely disappeared with sitting upright and improved by laying on the left side. Naso-laryngoscopy ruled out upper airway obstruction as a cause of stridor.Review of the chest CTA showed a right-sided aortic arch with aberrant left subclavian artery and Kommerell diverticulum. Tracheal narrowing was observed at two points. The proximal compression was caused by the anomalous aortic arch. The distal and severe narrowing involved the carina and both principal bronchi, right bronchus intermedius with complete right lower lobe atelectasis. The dynamic distal narrowing was due to interposition of central airways between widened thoracic aorta, the pulmonary artery and the heart. When supine, the heart would squeeze the interposed airways causing positon-dependent stridor.Due to recent ICH and contraindication for anticoagulation, the patient was not considered a surgical candidate. After hypertension was controlled, she was discharged with plan for surgical repair. DISCUSSION: Right-sided aortic arch is a rare congenital anomaly, reported in 0.1% of the population. It usually results from retained right fourth aortic arch and disappearance of the left fourth arch. The left subclavian artery has an aberrant origin arising from the remnant of the left aortic arch. This bulbous remnant at origin is called Kommerell diverticulum.Right-sided aortic arch is associated with congenital cyanotic heart disease, but majority of patients remain asymptomatic. Right-sided aortic arch with Kommerell diverticulum is a risk factor for aortic dissection. Atherosclerotic changes along with shear forces from the sharp aortic angle arch contribute to dissection. With the risk of dissection, surgical repair, including open, endovascular, or hybrid approaches, is the treatment for Kommerell diverticulum. CONCLUSIONS: Positional stridor can be an uncommon presentation of intrathoracic airway compression by dissecting aortic aneurysm. Right-sided aortic arch and Kommerell diverticulum are anomalies that contribute to the development of such compression. Reference #1: Herway, Seth T., Jonathan L. Benumof, Eugene Golts, and Gerard R. Manecke. 2015. "Major Positional Obstruction of the Trachea in a Patient with a Right-Sided Aortic Arch and Kommerell's Diverticulum." Journal of Cardiothoracic and Vascular Anesthesia 29(1):146-48. Retrieved (https://doi.org/10.1053/j.jvca.2013.08.003). Reference #2: Lin, Feng, Chang Chih Chen, Yu Jang Su, Yen Chun Lai, and Wen H. Chang. 2010. "Ruptured Aortic Aneurysm Presenting as a Stridor." International Journal of Gerontology 4(2):96-98. Reference #3: Kumar, Alok, Vikas Dutta, Sunder Negi, and GD Puri. 2016. "Vascular Airway Compression Management in a Case of Aortic Arch and Descending Thoracic Aortic Aneurysm." Annals of Cardiac Anaesthesia 19(3):568. Retrieved (http://www.annals.in/text.asp?2016/19/3/568/185568). DISCLOSURES: No relevant relationships by TsunKang Chiang, source=Web Response No relevant relationships by Ismail Dreshaj, source=Web Response No relevant relationships by Deb Leizman, source=Admin input No relevant relationships by Ramy Masroujeh, source=Web Response