Systolic blood pressure normal but diastolic high

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A. This question comes up often, perhaps because doctors and patients alike tend to pay more attention to the top (first) number, known as systolic pressure. It reflects the amount of pressure inside the arteries as the heart contracts. The bottom (second) number, diastolic pressure, is always lower since it reflects the pressure inside the arteries during the resting phase between heartbeats.

As it turns out, both systolic and diastolic blood pressure are important. Per the most recent guidelines, you have what's called elevated blood pressure if your systolic blood pressure reading is 120 to 129 mm Hg (which stands for millimeters of mercury). Once your systolic reading reaches 130 or higher or your diastolic reading is 80 or higher, you're considered to have high blood pressure, or hypertension.

Most people have what's known as essential or primary hypertension, which means it's not caused by a medical condition, medication, or substance. Primary hypertension can affect both systolic and diastolic pressure to a similar degree. But sometimes, especially in older people, it affects mainly the systolic pressure; this is called isolated systolic hypertension.

Why does this happen? As you age, your arteries tend to become less elastic and less able to accommodate surges of blood. Blood flowing through your arteries at high pressure can damage the inner lining of these vessels, accelerating the buildup of cholesterol-laden plaque. This further stiffens and narrows the arteries, a condition known as atherosclerosis. Because the same volume of blood has to pass through a smaller area, the systolic pressure tends to rise, while the diastolic pressure remains the same or gradually falls over time. In some people with isolated systolic hypertension, the diastolic pressure reading may drop into the 50s or even the 40s.

Most studies show a greater risk of cardiovascular disease (especially strokes) related to high systolic pressure as opposed to elevated diastolic pressure. But in 2019, an eight-year-long study involving more than 1.3 million adults found that while elevated systolic pressure had a greater effect on cardiac outcomes, high diastolic readings also affected a person's risk, regardless of the systolic reading.

To ensure accurate readings when you're checking your blood pressure at home, be sure to sit comfortably with your back supported, your feet flat on the floor, and your arm resting on a table with your palm facing up. If needed, support your arm with a pillow so that your elbow is at the level of your heart.

— Deepak L. Bhatt, M.D., M.P.H.
Editor in Chief, Harvard Heart Letter

Image: © Vadim Zhakupov/Getty Images

High Blood Pressure/Hypertension

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What is high blood pressure?

Blood pressure is the force of the blood pushing against the artery walls. The force is made with each heartbeat as blood is pumped from the heart into the blood vessels.  This is called systolic blood pressure. Blood pressure is also affected by the size of the artery walls and their elasticity. Each time the heart beats (contracts and relaxes), pressure is created inside the arteries.  When the heart is relaxed, the arteries stay at a lower resting tone to maintain some pressure in the artery. This is called diastolic blood pressure. 

High blood pressure is when the force of the blood is too high during heart contraction or relaxation within the arteries. The arteries may have an increased resistance against the flow of blood. This causes your heart to pump harder to circulate the blood.

What causes high blood pressure?

These factors may cause high blood pressure:

• Being overweight
• Having lots of salt in your diet
• Not getting much physical activity
• Family history of high blood pressure
• High stress levels
• Not getting enough sleep
• Excessive alcohol use
• Kidney disease

Who is at risk for high blood pressure?

More than half of all adult Americans have high blood pressure. You are at risk for it if you:

• Have diabetes, gout, or kidney disease
• Are African American, especially if you live in the southeastern U.S.
• Are middle-aged or older
• Have a family history of high blood pressure
• Eat a lot of high-salt foods
• Are overweight
• Drink a lot of alcohol
• Take birth control pills (oral contraceptives)
• Have depression
• Are pregnant
• Smoke or use e-cigarettes
• Use stimulant drugs such as cocaine or methamphetamine

What are the symptoms of high blood pressure?

High blood pressure often has no symptoms. But you can find out if your blood pressure is higher than normal by checking it yourself or by having it checked regularly by your healthcare provider.

Very high blood pressure can cause symptoms. These include headache, changes in vision, or chest pain.

How is high blood pressure diagnosed?

Blood pressure is measured with a blood pressure cuff and stethoscope by a nurse or other healthcare provider. You can also take your own blood pressure with an electronic blood pressure monitor. You can find one at most pharmacies.

Two numbers are recorded when measuring blood pressure:

• The top number is the systolic pressure. This is the pressure inside the artery when the heart contracts and pumps blood through the body.
• The bottom number is the diastolic pressure. This is the pressure inside the artery when the heart is at rest and is filling with blood.

Both the systolic and diastolic pressures are recorded as mm Hg (millimeters of mercury). This recording represents how high the mercury column in the blood pressure cuff is raised by the pressure of the blood.

Blood pressure is rated as normal, elevated, or stage 1 or stage 2 high blood pressure:

• Normal blood pressure is systolic of less than 120 and diastolic of less than 80 (120/80).
• Elevated blood pressure is systolic of 120 to 129 and diastolic less than 80.
• Stage 1 high blood pressure is when systolic is 130 to 139 or diastolic is 80 to 89.
• Stage 2 high blood pressure is when systolic is 140 or higher or diastolic is 90 or higher.

Even higher blood pressure (with the systolic blood pressure 180 or higher, the diastolic blood pressure more than 120, or both) is called a hypertensive urgency if there are no related symptoms. Or it's called a hypertensive emergency if there are symptoms indicating damage to the brain, heart, or kidneys. If you have a hypertensive urgency, you may need a change in your medicine right away or be evaluated in an emergency room. If you have a hypertensive emergency, you will need to be evaluated in an emergency room; and likely have a stay in the hospital.

A single higher blood pressure measurement does not always mean you have a problem. Your healthcare provider will want to see several blood pressure measurements over a number of days or weeks before diagnosing high blood pressure and starting treatment. Ask your provider when you should call if your blood pressure readings are not in the normal range.

How is high blood pressure treated? 

Treatment for high blood pressure may involve:

Lifestyle changes

These healthy steps can help you control your blood pressure:

• Choose foods that are low in salt (sodium).
• Choose foods low in calories and fat.
• Choose foods high in fiber.
• Stay at a healthy weight, or lose weight if you are overweight.
• Limit serving sizes.
• Get more exercise.
• Drink fewer or no alcoholic beverages.
• Reduce stress.
• Get enough quality sleep.
• Quit Smoking.

Certain medicines

Sometimes you may need to take 1 or more daily medicines to control high blood pressure. Take it exactly as directed.

If you have high blood pressure, have your blood pressure checked routinely and see your healthcare provider to watch the condition.

What are possible complications of high blood pressure?

High blood pressure raises your risk for:

• Heart attack
• Heart failure
• Stroke
• Kidney failure
• Loss of eyesight
• Death

How do I prevent high blood pressure?

You can help prevent high blood pressure with many of the same healthy steps used to treat it. These are:

• Cut back on salt (sodium) in your diet.
• Eat foods that are low in calories and fat, and high in fiber.
• Stay at a healthy weight, or losing weight if you are overweight.
• Exercise more.
• Stop smoking tobacco and e-cigarettes.
• Drink fewer or no alcoholic beverages.
• Get enough sleep.
• Don’t use stimulants or illegal drugs.

Key points about high blood pressure

• High blood pressure is when the force of the blood pushing against the artery walls is too high. This causes your heart to pump harder to circulate the blood.
• Risk factors include being overweight, having a family history of the disease, and being older.
• There are often no symptoms.
• Two numbers are recorded when measuring blood pressure. High blood pressure is when the top number (systolic pressure) is 130 or higher or the bottom number (diastolic pressure) is 80 or higher.
• Lifestyle changes and medicines may help treat high blood pressure.

Next steps

Tips to help you get the most from a visit to your healthcare provider:

• Know the reason for your visit and what you want to happen.
• Before your visit, write down questions you want answered.
• Bring someone with you to help you ask questions and remember what your provider tells you.
• At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you.
• Know why a new medicine or treatment is prescribed, and how it will help you. Also know what the side effects are.
• Ask if your condition can be treated in other ways.
• Know why a test or procedure is recommended and what the results could mean.
• Know what to expect if you do not take the medicine or have the test or procedure.
• If you have a follow-up appointment, write down the date, time, and purpose for that visit.
• Know how you can contact your provider if you have questions.

Medical Reviewer: Steven Kang MD

Medical Reviewer: Ronald Karlin MD

Medical Reviewer: Stacey Wojcik MBA BSN RN

© 2000-2022 The StayWell Company, LLC. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.

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