Why It Matters Where Your Blood Pressure Readings Are Taken

You check your own blood pressure using one of the machines at the pharmacy, and the reading is normal. But when the nurse at the doctor’s office takes a reading during your physical, the numbers are on the high side — and your doctor is concerned. So what gives? How can your blood pressure be fine one day and then a potential concern the next? There are actually a number of reasons that your blood pressure can change from day to day (or even from hour to hour) and some of them are a cause for concern.

White-Coat Hypertension

With the widespread availability of home blood pressure monitors, it’s easier than ever for people to keep track of their own numbers at home. People who have heart disease or another condition that requires continuous monitoring, for example, may find it easier to measure blood pressure at home than make regular trips to the doctor’s office. However, it’s quite common for home readings to be vastly different from the readings at the doctor’s office. Some of the most common causes include user error — medical personnel are trained in using blood pressure cuffs and taking accurate readings — and environmental. In some cases, the environment at home can cause a higher reading; spouses, children and the demands of home can all cause a spike in blood pressure. For these people, a visit to the doctor’s office may represent a welcome respite, which results in a lower reading. More common, though, is a phenomenon called “white coat hypertension.” For many people, the simple act of walking into an exam room increases stress, which can cause the heart to beat faster and increase blood pressure. For that reason, many doctors opt to check patients’ blood pressure at the beginning and end of the appointment to determine whether an initially high reading is actually an issue, or just a case of situational hypertension. If the readings are still high, the doctor may opt to explore further treatment, including prescription medication to lower blood pressure.

A More Serious Issue

While user error and situational factors can cause spikes in blood pressure that aren’t a cause for concern, a significant difference in blood pressure between the right and left arms could signal a very serious condition. For most people, it doesn’t matter whether blood pressure readings are taken in the right or the left arm. While there might be slight differences in the readings between arms, in general, blood pressure should be about the same in both arms because blood is pumped to all areas of the body at the same rate. However, more doctors are beginning to check patients’ blood pressure twice, once in each arm, especially those patients who have a history of hypertension. If each arm has a vastly different reading of greater than 10 points, particularly the systolic pressure (the upper number), there could be a blockage in one of the arteries that runs under the collarbone and brings blood to the arms, legs and brain. If there is in fact a blockage, you could be at a higher risk for stroke, peripheral artery disease and other cardiovascular events, including heart attack. According to a British study, it doesn’t matter which arm has the higher pressure when it comes to determining risk, but the amount of the difference between the arms that causes the most concern. A difference in systolic pressure of at least 10 points or more increased the risk of several problems, including:

• Peripheral artery disease, or a hardening or narrowing of the arteries that lead to the lower extremities;  people with different blood pressure readings are 2.5 times more likely to have reduced blood flow to their legs
• Differing blood pressure readings mean 1.6 times the risk of decreased blood flow to the brain, which increased stroke risk
• A 70 percent increased risk of dying from cardiovascular disease

In short, while a difference of a point or two between arms isn’t a cause for concern — anxiety or environmental factors can create different readings — a major difference should trigger additional intervention and testing to prevent serious complications.

Reducing Risk

Because varying blood pressure readings is such a strong predictor of cardiovascular disease, some groups, including the , recommend that doctors make checking blood pressure in both arms a standard practice. As a patient, you can help ensure that your blood pressure readings are accurate no matter which arm is checked by avoiding caffeine, nicotine and alcohol for 30 minutes before the test. Try to sit quietly and relax for a few moments before testing; if you’re at the doctor’s office, tell the doctor or nurse about any recent stressors (like traffic) that could create an artificially high reading. Rest your back on the chair with your feet on the floor, and make sure your arm is supported with your elbow level with your heart. High blood pressure isn’t something to be taken lightly, and it’s important to get accurate readings in both arms. If you’re concerned, ask your doctor to double check or take your own readings at home. Your cardiovascular health is too important to be left to chance.