Blood Pressure - normal, prehypertension, hypertension, what is the risk?

According to a study published in Stroke: Journal of the American Heart Association, “If we were to eliminate prehypertension, we could potentially prevent about 47 percent of all heart attacks,” said the study’s lead author Adnan I. Qureshi, M.D., professor and director of the Cerebrovascular Program in the Zeenat Qureshi Stroke Research Center at the University of Medicine and Dentistry of New Jersey in Newark.

Because even pre-hypertension triples heart attack risk, it is important to know if your blood pressure is normal.

From a Stroke Journal Report, 08/05/2005
"Normal blood pressure is lower than 120/80 millimeters of mercury (mm Hg). Prehypertension is systolic blood pressure between 120 and 139 and/or diastolic pressure between 80 and 89 mm Hg. (Systolic pressure is the force in the arteries when the heart beats and diastolic pressure is the force when the heart is at rest.) Hypertension is blood pressure 140/90 mm Hg or higher."