23 December 2025
: Case report 
Platypnea-Orthodeoxia Syndrome Associated With a Right-to-Left Cardiac Shunt Detected by Lung Perfusion Scintigraphy
Challenging differential diagnosis, Rare disease
Yusuke Nakano
ABCDEFG 1,2*, Hirohiko Ando CDE 1, Akinori Satake DE 3, Reiji Goto DE 1, Kentaro Mukai DE 1, Tetsuya Amano CDE 1
DOI: 10.12659/AJCR.949642
Am J Case Rep 2025; 26:e949642
Figure 2 Cardiac and scintigraphic findings. (A) Apical 4-chamber view on transthoracic echocardiography showing an enlarged aortic root (Ao) obscuring visualization of the right atrium, tricuspid valve, and interatrial septum, where a shunt would usually be identified. (B) Lung perfusion scintigraphy demonstrating technetium-99m (99mTc) particle uptake in the thyroid (middle) and kidneys (right) in addition to the lungs (left), indicating systemic distribution due to a right-to-left shunt. (C) Right atriography showing compression of the right atrium by the dilated ascending aorta (Ao). 99mTc – technetium-99m-labeled macroaggregated albumin; Ao – aorta; RV – right ventricle; LV – left ventricle; LA – left atrium; RA – right atrium.