What sign indicates aortic regurgitation during examination?

The sign that indicates aortic regurgitation during examination is widened pulse pressure. In aortic regurgitation, the diastolic pressure in the aorta decreases due to the backflow of blood from the left ventricle, while the systolic pressure can remain elevated due to the increased stroke volume. This results in a significant difference between systolic and diastolic pressures, thus creating a widened pulse pressure.

In terms of the other choices, pulsatile blanching and flushing of nail beds is more characteristic of other conditions like systemic hypotension or hyperdynamic circulation but is not specific to aortic regurgitation. Persistent systolic blood pressure does not accurately reflect the hemodynamic changes seen in aortic regurgitation, as the pulse pressure often becomes widened rather than remaining persistently high. Decreased cardiac output may occur in advanced cases of heart failure due to aortic regurgitation but is not a defining sign during the physical examination. Thus, the correct association with aortic regurgitation is indeed the presence of widened pulse pressure.