Dyspnea, worse when upright than when recumbent

shunting of blood (as seen in pulmonary, cardiac, or hepatic disease)

• After cardiac surgery, a 73 year old man developed cardiac tamponade localized to the right atrium, probably due to localized pericardial inflammation. This raised right atrial pressure and caused right-to-left shunting across a patent foramen ovale.
     Such cases may be hard to detect clinically without a detailed physical examination. In this case report, for example, the patient had a mean right atrial pressure of 12 cm H₂O in the cath lab, yet had "no jugular venous distension." These findings are at odds with each other. Please remember to examine carefully the neck veins. [101]
• This case report doesn't even include a description of the physical examination! With that caveat, this paper describes a 64 year old man who developed orthodeoxia and platypnea after cardiac surgery. Echocardiogram showed extrinsic compression of the right atrium and ventricle by a loculated pericardial effusion, plus right-to-left flow across the inter-atrial septum. Of note, however, the mean right atrial pressure was 10 and the mean left atrial pressure was 9 (as measured by the pulmonary capillary wedge pressure). In the absence of a right-to-left pressure gradient, the authors hypothesize that distortion of the right heart effectively aimed the effluent of the inferior vena cava directly at the foramen ovale when the patient was upright, causing shunting only in that position. The shunting stopped after the effusion resolved. [102]
• Another case of distorted cardiac anatomy leading, probably, to redirection of atrial inflow across a patent foramen ovale. [103]
• A persistent eustachian valve in the right atrium can cause right-to-left inter-atrial shunting in the presence of normal atrial pressures. [104]
• Found, in one patient, that a single bolus of methylene blue reduces pulmonary shunting in liver disease. Methylene blue blocks the vasodilatory effect of nitric oxide. [107]