High blood pressure (hypertension) is diagnosed when a patient’s blood is pushing too hard against the walls of the arteries. High blood pressure is a dangerous condition that is linked to heart attack, heart failure, stroke, kidney disease and other disorders.

Generally, high blood pressure is classified according to its cause. High blood pressure that has no known cause is called primary, or essential. Between 90 and 95 percent of cases of high blood pressure are primary.

High blood pressure that is caused by another disease or condition is known as secondary hypertension. For instance, renovascular hypertension is caused by kidney disease. There are also a number of other terms physicians use to describe high blood pressure, including malignant and labile. White coat hypertension is high blood pressure that only occurs in a physician's office, usually in response to stress associated with the test itself. 

High blood pressure is measured according to the cycle of the heart. The peak pressure, taken during the contraction phase of the heart, is known as systolic pressure. The lowest pressure, taken during the relaxation phase of the heart’s pumping action, is called the diastolic pressure. Blood pressure is expressed as systolic pressure over diastolic pressure (e.g., 120 millimeters of mercury (mmHg) over 80 mmHg). Each of these measurements is helpful to determine what kind of blood pressure might be present and how to best treat it.

Primary, or essential, hypertension is the most common form of high blood pressure, occurring in about 90 to 95 percent of cases. There is no known specific cause. However, there are several factors that – alone or in combination – can increase the risk of developing primary hypertension. These include:

Evidence also continues to build linking sodium intake with high blood pressure. Salt affects blood pressure because it causes the body to retain more water.

Normally, the kidneys flush this excess salt and water from the body. However, kidneys that are not functioning properly are unable to expel it sufficiently from the body, which will lead to fluid retention. Because the function of the kidneys is so closely tied with the body’s circulatory system, changes in blood pressure will prompt the kidneys to make an adjustment. If the kidneys malfunction and there is excess fluid in the system, hypertension can result.

Conversely, if high blood pressure exists, the kidneys may slow, and excess salt and fluid will collect in the body, adding further to the hypertension problem.

Underlying heart damage or dysfunction, including atherosclerosis, or a buildup of plaque within the artery walls, may add to the increased blood force against the artery walls. The pressure of the blood through these restricted passageways rises because of a lack of space. Higher blood pressure can also result if there is more blood relative to the size of the blood vessel.

White coat hypertension refers to mild hypertension that occurs in a physician's office, but does not occur at home. Generally, this is thought to be related to stress associated with the test itself. Previously, many experts considered white coat hypertension to be harmless. However, newer research is showing that white coat hypertension shares some similarities with essential hypertension and may slightly increase the risk of future heart problems.

Secondary hypertension is a condition in which the cause of the high blood pressure is known (e.g., sleep apnea or some forms of kidney or endocrine disease). The high blood pressure is secondary to another disease or disorder, and usually disappears once the underlying condition is controlled or cured. These underlying conditions include:

Other factors that could cause secondary hypertension include:

• Pregnancy (pregnancy-induced hypertension). Pregnancy can worsen the hypertension of women who already have it, or cause hypertension in women with no history of it. After the delivery, the high blood pressure tends to resolve in women with no prior history of it. However, women who developed pregnancy–induced hypertension have a higher risk of high blood pressure and stroke later in life.
  
  
• Certain medications. Prescription medications that can cause temporarily high blood pressure include certain nonsteroidal anti-inflammatory drugs (NSAIDs) and estrogen (in either oral contraceptives or hormone replacement therapy). Over-the-counter (OTC) medications that can cause the same effect include NSAIDS (e.g., ibuprofen or naproxen), cold, cough and sinus medications and many eye drops.
  
  
• Cocaine use. Not only can cocaine cause blood pressure to rise sharply, it can also cause heart attack and stroke in healthy people of any age.
  
  
• Long-term overuse of alcohol, caffeine or real licorice, which contains a steroid-like substance.
  
  
• Smoking.
  
  
• Stress.
  
  
• Very strenuous exercise, especially lifting heavy weights (temporarily, while straining).
  
  
• Exposure to lead, particularly among middle-aged and postmenopausal women.

Renovascular hypertension is one of the most common forms of secondary hypertension and is due to a decreased blood flow to the kidneys. Usually, this blood flow is restricted because the artery to the kidneys has narrowed (renal artery stenosis).

Renal blood vessels narrow because of one of two conditions – atherosclerosis or fibromuscular dysplasia. Atherosclerosis is a disease in which arteries are hardened and narrowed as a result of plaque that has built up along the inside of the artery walls. Fibromuscular dysplasia is a condition in which cells from the artery wall overgrow, causing the artery to narrow.

Diagnosis of renovascular hypertension can be difficult because symptoms tend to be subtle or absent. However, it is very important to diagnose this condition because some medications used to treat high blood pressure may be detrimental or lethal if given to patients with severe renal artery stenosis. Renal artery stenosis may be treated with angioplasty or stenting.

Labile, or transient, hypertension is a temporary rise in blood pressure during stressful situations. Blood pressure then returns to normal. Many young people who have labile hypertension for several years go on to develop primary hypertension, especially if there is a family history of hypertension. However, even labile hypertension may result in complications such as heart disease, kidney disease and stroke if left untreated. It is often treated successfully with beta blockers or other medications and stress management.

Isolated systolic hypertension (ISH) indicates that only the systolic blood pressure (the top number of a blood pressure reading) is elevated. ISH occurs mainly in older people because systolic pressure increases with age, whereas diastolic pressure can decline after age 55.

ISH patients have a rise in systolic pressure (above 140) but diastolic pressure remains normal. ISH is a common cause of stroke, and some studies suggest that it is probably a more important cause of stroke and heart attack than diastolic hypertension.

Until the year 2000, high blood pressure was generally diagnosed by paying attention to people’s diastolic blood pressure. For this reason, some people believe that a larger number of ISH cases may have gone undiagnosed.

Malignant, or accelerated, hypertension occurs in less than 1 percent of hypertensive patients. It is defined as a sudden rise in diastolic blood pressure to over 120. This very high diastolic blood pressure can be associated with damage to the brain, heart, eyes and kidneys.

The condition is considered life threatening, and immediate medical attention is extremely important. Treatment generally requires intensive care hospitalization with potent medications delivered through an intravenous (I.V.) line to take effect as quickly as possible. Symptoms include loss of vision, nausea, drowsiness, confusion and headache.

Resistant hypertension is high blood pressure that does not respond to typical treatments and therapies. Because of this, it is difficult to control and often requires lifestyle changes and two or three medications. People with resistant hypertension are urged to work closely with the physician who manages their condition and to carefully follow all of the physician’s orders regarding diet, exercise and medications.

Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions related to types of high blood pressure:

1. How high is my blood pressure?
   
   
2. Are these blood pressure levels too high? Are they too low?
   
   
3. Is it possible my blood pressure appears to be high because I am nervous? Are there any other tests I can take to get a more accurate reading?
   
   
4. Am I at high risk for high blood pressure?
   
   
5. Does high blood pressure put me at risk for any other cardiovascular conditions? Which ones?
   
   
6. Am I currently taking any medications that might be contributing to my high blood pressure?
   
   
7. Are there any medications I can take to lower my blood pressure? Are there side effects associated with any of these medications?
   
   
8. Are there any lifestyle changes I can make to lower my blood pressure or reduce my chances of developing high blood pressure? Should I quit smoking? Should I lose weight?
   
   
9. Could my high blood pressure be a result of my pregnancy? Could my blood pressure come down following the birth of my child?
   
   
10. How urgently do I need to lower my blood pressure?