About one in three adults has high blood pressure (hypertension), defined as a systolic blood pressure of 140 mm Hg or higher or a diastolic blood pressure of 90 mm Hg or higher. Systolic blood pressure, the upper number in a blood pressure reading, is the pressure in the arteries when the heart is contracting and pumping blood. Diastolic blood pressure, the lower number, is the arterial pressure when the heart relaxes between beats.
Even though high blood pressure usually has no symptoms, it forces your heart to work harder. It causes the left ventricle of the heart to enlarge, so that it requires a greater supply of blood. At the same time, hypertension increases the development of atherosclerosis, reducing the amount of blood that reaches the heart.
About half of people with a first heart attack have very high blood pressure (above 160/95 mm Hg). If your blood pressure is greater than 140/90 mm Hg, you need to lower it —ideally to less than 120/80 mm Hg. Your doctor can help you do this with a combination of lifestyle measures and blood pressure-lowering medications. Lowering your blood pressure will reduce your risk of a heart attack, heart failure, and stroke. In addition, if you have kidney disease, controlling blood pressure can help prevent the disease from progressing.
Isolated Systolic Hypertension
You should pay particular attention to the top number of your blood pressure reading —your systolic blood pressure —because it predicts the risk of a heart attack better than diastolic pressure. Many individuals over age 50 have a condition called isolated systolic hypertension —diastolic blood pressure is normal (below 90 mm Hg) but systolic blood pressure is elevated (above 140 mm Hg). This type of hypertension is associated with a high risk of heart attacks. Reducing systolic blood pressure with lifestyle measures and medication can lower this risk.
Your doctor might also mention a condition called prehypertension —a systolic blood pressure between 120 and 139 mm Hg or diastolic blood pressure between 80 and 89 mm Hg. If your blood pressure is in this range (about 70 million American adults have prehypertension), you are more likely to develop high blood pressure and are at greater risk for a heart attack than those with lower blood pressures. People with prehypertension should try to lower their blood pressure to below 120/80 mm Hg through such lifestyle measures as a healthy diet (low in sodium and rich in fruits, vegetables, and low-fat dairy products), regular physical activity, smoking cessation, and weight control.