top number of blood pressure mean
For example, 120/80. The top number refers to the amount of pressure in your arteries during contraction of your heart muscle. This is called systolic pressure. The bottom number refers to your blood pressure when your heart muscle is between beats. This is called diastolic pressure.
In the past, it was commonly thought that the diastolic pressure or bottom number was the most important blood pressure number. This mistaken idea dates back to one of the early studies of the treatment of blood pressure, where only patients with diastolic blood pressure over 90 mm were allowed into the study.