Some people have blood pressure that stays up all or most of the time. Their blood pushes against the walls of their arteries with higher than normal force. High blood pressure harms the arteries by making them thick and stiff. This speeds up the build up of cholesterol and fats in the blood vessels like rust in a pipe, which prevents the blood from flowing through the body, and in time can lead to a heart attack or stroke.
Blood carries oxygen to the body.
When the arteries that bring blood to the heart muscle become blocked, the heart cannot get enough oxygen. Eventually, the flow may be stopped completely, causing a heart attack. High blood pressure causes the heart to work harder. Over time, this causes the heart to thicken and stretch. Eventually the heart fails to function normally causing fluids to back up into the lungs.