Minute differences in the blood pressure between each arm aren’t cause for concern, but there is a point at which variances could represent cardiovascular trouble. An expansive international study has shone new light on where that point lies, drawing on data from more than 50,000 subjects around the world. The research is claimed to be the first to find that the greater this differential in arm blood pressure, the greater the patient’s risk of heart attack, stroke and early death.
As it stands, hypertension guidelines recommend that physicians record blood pressure in both arms at the initial consultation, and if there is a difference of greater than 20 mmHg (millimeters of mercury), then further investigation is warranted. The reasoning behind this is that large differences in blood pressure measurements may be a sign of blocked or stiffening arteries, or some other factor affecting blood flow.
According to the authors of the new study, led by the University of Exeter, these guidelines are “widely ignored,” and their review of global health data, called the INTERPRESS-IPD Collaboration, suggests the threshold may be too high.
“We’ve long known that a difference in blood pressure between the two arms is linked to poorer health outcomes,” says lead author Dr Chris Clark. “The large numbers involved in the INTERPRESS-IPD study help us to understand this in more detail. It tells us that the higher the difference in blood pressure between arms, the greater the cardiovascular risk, so it really is critical to measure both arms to establish which patients may be at significantly increased risk. Patients who require a blood pressure check should now expect that it’s checked in both arms, at least once.”
Clark and his colleagues arrived at this conclusion after conducting a meta-analysis of data from 24 global studies, concerning nearly 54,000 people from Europe, the US, Africa and Asia. Blood pressure data on both arms was available for this entire group, enabling the team to investigate how inter-arm differences tracked with heart attacks, strokes and death over a 10-year period.
In doing so, the team found that every mmHg of difference between the systolic, or maximum, pressure, in each arm corresponded with a one percent increase in the subject’s chance of experiencing new angina, a heart attack or stroke in the following 10 years. In this way, the authors describe this study as the first to establish that the greater the inter-arm blood pressure difference, the higher the additional health risk to the patient.
While a difference of 20 mmHg is the threshold laid out in the international hypertension guidelines, some countries take a more stringent approach, such as in the UK and Europe where guidelines stipulate 15 mmHg indicates additional cardiovascular risk, or advice from the Mayo Clinic, which states that repeated differences of 10 to 15 mmHg are indicative of likely vascular disease.
“We believe that a 10 mmHg difference can now reasonably be regarded as an upper limit of normal for systolic inter-arm blood pressure, when both arms are measured in sequence during routine clinical appointments,” says co-author Professor Victor Aboyans. “This information should be incorporated into future guidelines and clinical practice in assessing cardiovascular risk. It would mean many more people were considered for treatment that could reduce their risk of heart attack, stroke and death.”
The research was published in the journal Hypertension.
Source: University of Exeter