Odds are that when your doctor takes your blood pressure, he or she measures it in only one arm. Yet, guidelines from the American Heart Association have for some time recommended measuring pressure in both arms at a patient’' initial visit—and findings from a recent study suggest why clinicians should routinely perform the two-arm measurement.

The study, published in the Lancet, found that a substantial difference in blood pressure readings between arms indicates an increased risk of developing vascular disease and of dying from heart disease. A gap between arms in readings of systolic pressure—the top number in the reading, which measures pressure in the arteries when the heart muscle contracts, or beats—can reveal impaired blood flow stemming from vascular diseases, specifically peripheral arterial disease (PAD) and cerebrovascular disease.

When researchers analyzed data from 20 studies involving 16,428 people, they found that a difference of 15 millimeters of mercury (mm Hg) or greater between arms was associated with more than twice the risk of developing PAD when compared with people who had smaller systolic variations. PAD occurs when plaque builds up in the arteries (atherosclerosis), mostly affecting the legs. The blockages, similar to coronary artery disease, increase the risk of a heart attack or stroke. In its early stages, PAD is often symptomless.

By identifying high-risk patients early, doctors can test them for PAD and suggest ways to reduce risk, like quitting smoking, lowering blood pressure and taking statins to improve cholesterol levels.

The study analysis also showed that a difference of 15 mm Hg or more was associated with underlying cerebrovascular disease caused by atherosclerosis in the arteries that deliver blood to the brain, which can lead to stroke or dementia. People in the study with at least a 15 mm Hg difference had a 60 percent increased risk of suffering from the disease. The difference of 15 mm Hg or more was also associated with a heightened likelihood of premature death from heart disease or another medical condition.

And the number of people showing such a gap wasn't insignificant. In one study the researchers analyzed for the Lancet study, up to 7 percent of participants had a difference of 15 mm Hg or higher.

Minding the blood pressure gap

More research—including studies involving diastolic pressure (the lower number in a blood pressure reading)—is needed to assess how aggressively patients should manage risk factors based on an arm gap in blood pressure readings. But another compelling reason to check for a pressure difference between arms is to accurately identify the presence of hypertension, or high blood pressure. If a clinician measures blood pressure in only one arm, and the pressure is lower in that arm than in the other, he or she may miss hypertension.

For that reason, as well as for potentially identifying a sign of vascular disease, having your blood pressure measured in both arms is certainly worth discussing with your doctor at your next visit.

A word about white-coat hypertension

When some people visit their doctors, they may feel anxious, which can cause an abnormal rise in blood pressure. This is known as white-coat hypertension. If your doctor suspects this, he or she may ask you to take your own blood pressure readings at home, over several days at various times of day.

Your doctor can then compare your home readings with office readings to determine whether an elevated level is a white-coat effect. You should use a high-quality, upper-arm digital blood pressure monitor, such as a model manufactured by Omron or Panasonic, and have it calibrated at your doctor's office before first use.

Source: Prepared by the Editors of The Johns Hopkins Medical Letter: Health After 50

Publication Review By: the Editorial Staff at Healthcommunities.com

Published: 15 Jul 2013

Last Modified: 15 Jul 2013