Why You Must Get a Blood Pressure Reading In Both Arms

People whose systolic blood pressure the upper number in their reading is different in their left and right arms may be suffering from a vascular disease that could increase their risk of death, British researchers report.

The arteries under the collarbone supply blood to the arms, legs and brain. Blockage can lead to stroke and other problems, the researchers noted, and measuring blood pressure in both arms should be routine.

"This is an important finding) for the general public and for primary care doctors," said William O'Neill, MD, a professor of cardiology and executive dean of clinical affairs at the University of Miami Miller School of Medicine.

The arteries that run under the collarbone can get blocked, especially in smokers and people with diabetes, he noted. "If one artery is more blocked than the other, then there is a difference in blood pressure in the arms," Dr. O'Neill explained.

"Doctors should, for adults-especially adult smokers and patients with diabetes-at some point check the blood pressure in both arms," he said. "If there is a difference it should be looked into further."

The report appeared in an online edition of The Lancet.

The Study

A team led by Christopher Clark, MD, from the Peninsula College of Medicine and Dentistry at the University of Exeter in England, reviewed 28 studies that looked at differences in systolic blood pressure between arms.

The analysis found that a difference of 15 millimeters of mercury (mmHg) or more between readings was linked with an increased risk of narrowing or hardening of the arteries supplying the lower limbs, called peripheral vascular disease.

The risk of reduced blood flow to the legs and feet was increased 25 times and the risk of decreased blood flow to the brain was in creased 1.6 times, the researchers found.

The difference in blood pressure was also associated with a 70% increased risk of dying from cardiovascular disease and a 60% increased risk of death from any cause, the authors added.

The risk of having peripheral vascular disease was also increased with a 10 mmHg difference in blood pressure between arms, the researchers noted.

It makes no difference which arm has the higher or lower pressure, it's the difference between them that matters, the study authors said.

Conclusions

Finding peripheral vascular disease early and treating it by lowering blood pressure and cholesterol as well as giving up smoking can help reduce the risk of death, Dr. Clark's group said.

"Our findings suggest that a difference in (systolic blood pressure) of 10 mmHg or more between arms could identify patients at high risk of asymptomatic peripheral vascular disease and mortality who might benefit from further assessment, the researchers concluded.

"Findings from our study should be incorporated into future guidelines for hypertension [high blood pressure) and blood pressure measurement," they added.

Another expert agreed that when it comes to blood pressure monitoring, both arms matter.

"These findings further reinforce blood pressure measurement guidelines of the American Heart Association, World Health Organization, International Society of Hypertension and European Society of Hypertension, which recommend that blood pressure should be measured in both arms at initial assessment," said Gregg Fonarow, MD, a professor of cardiology at the University of California, Los Angeles, and spokesperson for the American Heart Association.

According to Dr. Fonarow, individuals found to have differences in systolic blood pressure in between arms of greater than 10 or 15 mmHg should see their doctor for further tests.