Organ Damage in Different Types of High Blood Pressure

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The summary below is from the full report titled "Cardiac and Arterial Target Organ Damage in Adults with Elevated Ambulatory and Normal Office Blood Pressure." It is in the 19 October 1999 issue of Annals of Internal Medicine (volume 131, pages 564-572). The authors are J.E. Liu, M.J. Roman, R. Pini, J.E. Schwartz, T.G. Pickering, and R.B. Devereux.

What is the problem and what is known about it so far?

It is well known that blood pressure measurements can vary. Some people will have high blood pressure (hypertension) when they are in a doctor's office but normal blood pressure when measured in other settings. Doctors use the term "white coat hypertension" to describe this occurrence, since the blood pressure is only high when the patient sees the doctor and doctors often wear white coats when they see patients. It is also possible that a person could have normal blood pressures in the doctor's office but have high blood pressure at other times ("white coat normotension"). People whose blood pressure is high more often than it is normal are at increased risk for heart disease and strokes.

Why did the researchers do this particular study?

The researchers wanted to see how common it is for people to have normal blood pressures in doctors' offices but high blood pressures in other settings (white coat normotension). They also wanted to see if people with this condition are at risk for heart disease and strokes.

Who was studied?

295 adults who had normal blood pressures in doctors' offices and 64 adults who had definite high blood pressures (both in and out of the doctor's office).

How was the study done?

First, the researchers measured ambulatory blood pressure [the blood pressure outside the doctor's office] in the 295 people with normal office blood pressures. To do this, they had the people wear portable blood pressure monitors. These are small machines that measure and record blood pressure as people go about their usual activities. They found that 61 of these people had high ambulatory blood pressure even though they had normal blood pressure in their doctors' offices. This left them with three groups.: 1) people who had normal blood pressure in and out of doctors' offices, 2) people who had white coat normotension, and 3) people who had high blood pressure both in and out of doctors' offices.

To see if people with white coat normotension were at risk for heart attacks and strokes, they did special tests of their hearts and of their carotid arteries. The carotids are blood vessels in the neck that lead to the brain. With an echocardiogram (ultrasound tests of the heart), the researchers measured the thickness of the heart muscle. Thickened heart walls indicate that high blood pressure has damaged the heart. The researchers also did ultrasounds of the carotid arteries to look for plaques or blockages in these arteries. Strokes can occur if pieces of these plaques break off and block blood flow to the brain. Ultrasound tests use sound waves to create pictures of internal body parts.

What did the researchers find?

Adults with white coat normotension were older, were more overweight, had higher blood sugar levels, and had worse kidney function than those with normal blood pressure. They were also more likely to smoke. White coat normotension was more common in people with "high normal" blood pressure in their doctors' offices than it was among people who had blood pressure in the low to middle of the normal range.

The people with white coat normotension were as likely as those with definite hypertension to have abnormally thick heart walls and carotid artery plaques.

What are the implications of the study?

This study may help to explain why heart disease and strokes happen in some people who always have normal blood pressure in their doctor's offices. It also suggests that ambulatory blood pressure monitoring may be a better way to tell whether people have high blood pressure than measuring blood pressure during health care visits.