Friedreich's sign
From Infogalactic: the planetary knowledge core
In medicine, Friedreich's sign is the exaggerated drop in diastolic central venous pressure seen in constrictive pericarditis (particularly with a stiff calcified pericardium) and manifested as abrupt collapse of the neck veins or marked descent of the central venous pressure waveform.
The sign is named after Nikolaus Friedreich.[1]
References
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