Hill’s sign is based on the difference between the upper limb and lower limb arterial pressures recorded by the sphygmomanometer. Systolic pressure recorded from the lower limb is more than that from the upper limb. Difference in systolic pressure above 20 mm Hg is taken as significant. When Hill’s sign is taken for grading the severity of aortic regurgitation, the following classification is usually applied:
Mild AR: 20 – 40 mm Hg
Moderate AR: 40 – 60 mm Hg
Severe AR: More than 60 mm Hg