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Taking blood pressure measurements from both arms could help save lives, researchers have said.
UK experts found “strong evidence” that a difference in blood pressure between the two arms is linked to an increased risk of heart attack, stroke and death.
Their findings are based on data collected from 24 global studies of nearly 54,000 people, in Europe, the United States, Africa and Asia.
International blood pressure guidelines advise healthcare professionals to measure blood pressure in both arms when assessing cardiovascular risk, but this is “largely ignored,” experts say.
Current UK and European guidelines on what constitutes a risk in terms of blood pressure differences between arms, known as bilateral blood pressure, should be lowered by 15 to 10 millimeters of mercury (mmHg), they say.
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Strong evidence from a large international study confirms that a difference in blood pressure readings between arms is linked to an increased risk of heart attack, stroke, and death.
The new study provides a new upper limit of ‘normal’ for a difference between arms in blood pressure, which is significantly lower than the current guideline.
This could disrupt international guidelines for hypertension, meaning that more patients at risk could be identified and receive life-saving treatment.
“ Checking one arm and then the other with a commonly used blood pressure monitor is inexpensive and can be done in any healthcare setting, without the need for additional or expensive equipment, ” said study lead author Dr. Dr. Chris Clark, of the University of Exeter School of Medicine. .
“While international guidelines currently recommend that this be done, it only happens about half the time at best, usually due to time constraints.
“Our research shows that the little extra time it takes to measure both arms could ultimately save lives.”
The team did not set out to establish causality – whether bilateral high blood pressure causes blood health problems.
“We are not saying that a difference between the arms causes strokes or heart attacks,” Dr. Clark told MailOnline.
“We believe that a difference in blood pressure between the arms represents underlying differences in the health of the arteries (the brachial arteries) that we are using to measure arm blood pressure.”
High blood pressure, also known as hypertension, is one of the main risk factors for cardiovascular diseases, such as coronary artery disease and heart attacks.
Around a third of adults in the UK have high blood pressure, although many will not realize it, according to the NHS.
The British Heart Foundation put this estimate at just over a quarter, around 14.4 million adults in the UK.
While health experts have long known that a difference in blood pressure between the two arms is linked to poorer health outcomes, their study helps to understand this association in greater detail.
“It tells us that the greater the difference in blood pressure between the arms, the greater the cardiovascular risk, so it is critical to measure both arms to establish which patients may be at significantly higher risk,” said Dr. Clark.
“Patients who require blood pressure monitoring should now expect it to be monitored in both arms at least once.”
Blood pressure is a measure of the force the heart uses to pump blood throughout the body, rising and falling in a cycle with each pulse.
It is measured in units of millimeters of mercury (mmHg) and the reading is always given as two numbers: systolic pressure (the pressure when the heart expels blood) and diastolic pressure (the pressure when the heart rests between beats).
The systolic reading represents the maximum blood pressure and the diastolic reading is the minimum blood pressure.
A high systolic blood pressure in one arm only indicates hypertension.
In the image, the different categories of blood pressure, as detailed by the American Heart Association
Meanwhile, a significant difference between the systolic blood pressure measurements in the two arms could also be indicative of a narrowing or stiffening of the arteries, which can affect blood flow.
These arterial changes are recognized as an additional risk marker for subsequent heart attack, stroke or premature death, and should be investigated for treatment, according to the team.
“Evidence from previous studies by our group and others suggests that stiffening of the arteries may be the underlying process here,” Dr. Clark told MailOnline.
Hardening occurs early in the course of arterial disease and may not be symmetrical in the early stages.
“The systolic blood pressure measured in the arm will be affected (increased) if the artery becomes stiff, due to changes in the velocity of the pulse waves through the artery, which increase with stiffness.”
Arterial changes tend to occur at multiple sites, so differences in the health of the brachial arteries may be “a clue” to the status of other arteries, such as the cerebral or coronary, said Dr. Clark.
Both the UK and European guidelines recognize a systolic difference of 15 mmHg or more between the two arms as the threshold that is associated with additional cardiovascular risk.
Led by the University of Exeter, the scientists searched for studies that recorded blood pressure and bilateral results and created a single international data set, called the INTERPRESS-IPD Collaboration.
Data were pooled from 24 studies, with a total of 53,827 people analyzed
The data covered adults from Europe, the US, Africa, and Asia for whom blood pressure readings were available for both arms.
The team analyzed data on the difference in blood pressure between the arms and tracked the number of deaths, heart attacks and strokes that occurred in the cohort over 10 years.
The researchers found that a lower threshold of 10 mmHg was clearly indicative of additional risk, which “would mean that many more people should be considered for treatment if there is such a difference between the arms.”
Blood pressure is a measure of the force the heart uses to pump blood through the body, and it rises and falls in a cycle with each pulse.
“We believe that a difference of 10 mmHg can now be reasonably considered an upper limit of normal for systolic blood pressure between arms, when both arms are measured in sequence during routine clinical appointments,” said study co-author Professor Victor Aboyans at Dupuytren University Hospital in Limoges, France.
‘This information should be incorporated into future guidelines and clinical practice to assess cardiovascular risk.
“It would mean that many more people would be considered for treatment that could reduce their risk of heart attack, stroke and death.”
A difference between arms of more than 10 mmHg occurs in 11 percent of people with high blood pressure (hypertension) – itself a known health risk – and in 4 percent of the general population.
The study has been published in Hypertension.
