Which arm is best for reading blood pressure?
When most people think of having their blood pressure taken, they think of taking the reading from one arm. But a new study says blood pressure should be measured in both arms, and adopting the higher reading can improve hypertension diagnosis and management.
Research published in the journal Hypertension found that using the higher arm blood pressure reading reclassified 12.4 percent of people as having hypertension. According to the study, "Failure to measure both arms and use the higher reading arm will not only result in underdiagnosis and undertreatment of high blood pressure but also under-estimation of cardiovascular risks for millions of people worldwide." Yet, only 20 to 50 percent of patients reported having both arms measured, researchers said.
Cardiologist Jennifer Ladner, MD, a Cape Cod Hospital inpatient cardiologist, explained that taking blood pressure readings in both arms has long been the standard of care for new patients.
“Patients don’t have to have blood pressure readings in both arms every time they come to the office, but it should be done the very first time a person is seen in the office,” Dr. Ladner said.
There is always some variability between the two arms, she noted. It can be as much as 10 mm of mercury on the systolic pressure (top number), but if it’s more than 10mm, that can signal a problem.
In an older patient, if there is a significant difference in blood pressure between the two arms, that could be a sign of a potential problem such as a partial blockage in the artery that feeds the arm. In a younger patient, the problem could be genetic abnormalities, Dr. Ladner said.
While Dr. Ladner confirmed the study’s finding that the higher blood pressure reading is the accurate blood pressure, she added that it is important for your doctor to find out what’s causing any significant difference between the readings in both arms.
“I’ve had patients with a dramatic difference between the two arms—such as 100 mm of mercury,” she said. “That obviously makes a big difference in your treatment.”
Self-monitoring: One or two arms?
According to the American Heart Association, blood pressure numbers of less than 120/80 mm Hg are considered within the normal range. A doctor should evaluate low or elevated blood pressure.
Dr. Ladner tells her patients to stick with one arm and consistently use the same arm when checking their own blood pressure at home.
She recommends that patients who have a diagnosis of hypertension take their blood pressure periodically and keep a record for their doctors. Be sure to record both the date when you take your reading as well as the blood pressure reading. Monitoring your blood pressure at home empowers you to take the very best care of yourself, she said.
“Checking your own blood pressure at home is appropriate and helpful for the doctor,” Dr. Ladner said. “If you see your doctor every six months, check your blood pressure once a week or at least a couple times a month to make sure it’s where it should be.”
Often, people have higher blood pressure readings simply because of the stress of coming to see the doctor, she acknowledged, adding: “For this reason, the more accurate reading is more likely to be the readings from home where you’re in a normal setting.”
Dr. Ladner also suggests taking your blood pressure cuff to the doctor’s office and having a nurse check it against the office’s cuff to make sure it is accurate. This is especially important when you buy a new cuff.
“If you see your pressure is running high, then check more frequently,” she said. “See if there is a pattern. A higher reading may be because you’ve had too much salt in your diet lately, or it can mean you need a change in medication. Share your readings with your doctor.”
Getting an accurate reading
Did you know talking while having your blood pressure taken can elevate your reading by as much as 10 points? Dangling your feet from an exam table or kitchen stool can also throw off the reading.
Mistakes like this happen too often at doctors’ offices and at home, leading to this list that guides you through what to do to get an accurate reading.
The American Heart Association has teamed up with the American Medical Association to make helpful, easy-to-read information about understanding blood pressure readings here.
A Return to the Community Setting
For the past eight years, Dr. Ladner has worked at Cape Cod Hospital as an inpatient cardiologist, seeing only hospitalized patients. On May 1, she will return to community practice when she moves to the Cape Cod Healthcare Cardiovascular Center – Falmouth.
Patients will be able to choose her as their cardiologist once again, and Dr. Ladner will be one-on-one with their ongoing care—a change she said she looks forward to.
