Paradoxical orthodeoxia in a patient with a large thoracic aortic aneurysm.
BACKGROUND
Orthodeoxia is a rare clinical syndrome characterised by dyspnoea and arterial deoxygenation that accompanies a change from a supine to erect position.


METHODS
We describe an unusual case of "paradoxical orthodeoxia" in a 70-year-old man with a thoracic aortic aneurysm: arterial desaturation when supine that improved when erect.


RESULTS
Non-invasive imaging revealed compression of the left pulmonary artery by the aneurysm (thoracic computed tomography) and patent foramen ovale (transesophageal echocardiography). Nuclear studies show decreased relative left lung perfusion attributable to the former, and right-to-left atrial shunt attributable to the latter. The degree of right-to-left shunt increases in the supine position: nuclear pulmonary shunt study shows shunt extent of 21% when supine versus 10% erect.


CONCLUSIONS
A physioanatomical explanation is proposed.
Soon
Jia-Lin
JL
Department of Cardiothoracic Surgery, National Heart Centre, Singapore.
Tan
Ru-San
RS
Ng
David C E
DC
Kwek
Boon-Han
BH
Chua
Yeow-Leng
YL
D000368:Aged; D017545:Aortic Aneurysm, Thoracic / Q000453:epidemiology*; D004417:Dyspnea / Q000209:etiology; D017548:Echocardiography, Transesophageal; D005260:Female; D006344:Heart Septal Defects, Atrial / Q000453:epidemiology; D006801:Humans; D010100:Oxygen / Q000097:blood*; D011187:Posture / Q000502:physiology*; D016683:Supine Position / Q000502:physiology
D010100:Oxygen