Blood pressure is the pressure exerted by the blood on the walls of the blood vessels. Unless indicated otherwise, blood pressure is understood to mean arterial blood pressure, i.e. the pressure in the large arteries, such as the brachial artery (in the arm). The pressure of the blood in other vessels is lower than the arterial pressure.
The peak pressure in the arteries during the cardiac cycle is the systolic pressure, and the lowest pressure (at the resting phase of the cardiac cycle) is the diastolic pressure. Typical values for the arterial blood pressure of a resting, healthy adult are approximately 120 mmHg systolic and 80 mmHg diastolic (written as 120/80 mmHg), with large individual variations.
Signs and symptoms
Hypertensive urgencies and emergencies - Hypertension is rarely severe enough to cause symptoms. These only surface with a systolic blood pressure over 240 mmHg and/or a diastolic blood pressure over 120 mmHg. These pressures without signs of end-organ damage (such as renal failure) are termed accelerated hypertension. When end-organ damage is present, but in absence of raised intracranial pressure, it is called hypertensive urgency. Hypertension under this circumstance needs to be controlled, but hospitalization is not required. When hypertension causes increased intracranial pressure, it is called malignant hypertension. Increased intracranial pressure causes papilledema, which is visible on ophthalmoscopic examination of the retina.
Pregnancy - Although few women of childbearing age have high blood pressure, up to 10% develop hypertension of pregnancy. While generally benign, it may herald three complications of pregnancy: pre-eclampsia, HELLP syndrome and eclampsia. Follow-up and control with medication is therefore often necessary.
Hypertension - Hypertension is usually found incidentally - "case finding" by healthcare professionals. It normally produces no symptoms.
Malignant hypertension (or accelerated hypertension) is distinct as a late phase in the condition, and may present with headaches, blurred vision and end-organ damage.
It is recognised that stressful situations can increase the blood pressure; if a normally normotensive patient has a high blood pressure only when being reviewed by a health care professional, this is colloquially termed white coat effect. Since most of what we know of hypertension and its outcome with or without modification is based on large series of readings in doctors' offices and clinics (eg Framingham) it is difficult to be sure of the significance of white-coat hypertension. Ambulatory monitoring may help determine whether traffic and ticket inspectors produce similar sustained rises.
Hypertension is often confused with mental tension, stress and anxiety. While chronic anxiety is associated with poor outcomes in people with hypertension, it alone does not cause it.
Complications - While elevated blood pressure alone is not an illness, it often requires treatment due to its short- and long-term effects on many organs. The risk is increased for:
- Cerebrovascular accident (CVAs or strokes)
- Myocardial infarction (heart attack)
- Hypertensive cardiomyopathy (heart failure due to chronically high blood pressure)
- Hypertensive retinopathy - damage to the retina
- Hypertensive nephropathy - chronic renal failure due to chronically high blood pressure
- Heavy alcohol use
- Renal artery stenosis
- Obstructive sleep apnea
- Hyperaldosteronism (Conn's syndrome)
- Cushing's disease
- Steroid use
- Coarcation of the aorta
- Being overweight
- Having a family history of high pressure
- Being of African-American descent
- Having an inactive lifestyle
- Drinking too much alcohol
- Having too much salt or not enough potassium, calcium or magnesium in your diet
- Certain medications, especially birth control pills, steroids, decongestants and anti-inflammatory drugs
- Maintain a healthy weight. If you are overweight, even losing 10 pounds can help lower your blood pressure
- Exercise regularly
- Drink alcohol only in moderation
- Use salt moderately
- Eat plenty of fruits, vegetables, legumes and low-fat dairy products to ensure you get enough potassium, calcium, and magnesium in your diet.
- Reduce the saturated fat in your diet (found in milk, cheese and meat)
- Stop using tobacco products - Learn how to check your own blood pressure.