What does the Quincke sign represent?

The Quincke sign specifically refers to the observable pulsations of the nail bed, which are indicative of significant changes in blood flow or pressure. This sign is most commonly associated with conditions that result in an increase in stroke volume, such as aortic regurgitation. In patients with this condition, the inefficacy of the valve leads to a backflow of blood into the left ventricle during diastole, causing a rise in the stroke volume that can be reflected in the peripheral circulation.

When assessed, the nails may appear to have a rhythmic pulsation, which is visible when pressure is applied. This phenomenon is particularly striking in individuals whose cardiovascular health is compromised, making it a useful clinical observation. Quincke sign is not directly related to other options provided, such as the audible diastolic murmur, which pertains to heart sounds rather than physical signs in the extremities, or neonatal failure to thrive, which refers to a pediatric condition with different underlying causes.