Led by the University of Exeter, the global INTERPRESS-IPD Collaboration conducted a meta-analysis of all the available research, then merged data from 24 global studies to create a database of nearly 54,000 people.
The data spanned adults from Europe, the US, Africa and Asia for whom blood pressure readings for both arms were available.
Funded by the National Institute for Health Research (NIHR) and published today in Hypertension, the study is the first to conclude that the greater the inter-arm blood pressure difference, the greater the patient’s additional health risk.
Currently, international blood pressure guidelines advise health professionals to measure blood pressure in both arms when assessing cardiovascular risk,- yet this is widely ignored.
The new study provides a new upper limit of ‘normal’ for an inter-arm difference in blood pressure, which is significantly lower than the current guidance.
The research could lead to a change in international hypertension guidelines, meaning more at-risk patients could be identified and receive potentially life-saving treatment.
In a methodology that put patients at its heart, working with a patient advisory group at every step of the research, the team analysed data on inter-arm blood pressure difference, and tracked the number of deaths, heart attacks and strokes that occurred in the cohort over 10 years.
Lead author and GP Dr. Chris Clark, of the University of Exeter Medical School, said: “Checking one arm then the other with a routinely used blood pressure monitor is cheap and can be carried out in any healthcare setting, without the need for additional or expensive equipment.
Whilst international guidelines currently recommend that this is done, it only happens around half of 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”.
“We’ve long known that a difference in blood pressure between the two arms is linked to poorer health outcomes.
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.”
Blood pressure rises and falls in a cycle with each pulse. It is measured in units of millimetres of mercury (mmHg), and the reading is always given as two numbers: the upper (systolic) reading represents the maximum blood pressure and the lower (diastolic) value is the minimum blood pressure.
A high systolic blood pressure indicates hypertension. This affects one third of the adult population and is the single leading cause globally of preventable heart attacks, strokes and deaths.
A significant difference between the systolic blood pressure measurements in the two arms could be indicative of a narrowing, or a stiffening, of the arteries, which can affect blood flow.
These arterial changes are recognised as a further risk marker for subsequent heart attack, stroke or early death, and should be investigated for treatment.
The researchers concluded that each mmHg difference found between the two arms, elevated predicted 10-year risk of one of the following occurring by one percent; new angina, a heart attack or stroke.
At the moment, both UK and European guidelines recognise a systolic difference of 15 mmHg or more between the two arms as the threshold indicative of additional cardiovascular risk. This new study found that a lower threshold of 10 mmHg was clearly indicative of additional risk, which would mean that far more people should be considered for treatment if such a difference between arms is present.
To this end, the research team has created a tool that is easy for clinicians to use, to establish who should be considered for treatment based on their risk, incorporating the blood pressure reading in both arms.
Research co-author Professor Victor Aboyans, head of the department of cardiology at the Dupuytren University Hospital in Limoges, France, said “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.
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.”
An interarm difference of greater than 10 mmHg occurs in 11 percent of people with high blood pressure (hypertension) – itself a known health risk – and in four percent of the general population.
The paper is entitled “Associations Between Systolic Interarm Differences in Blood Pressure and Cardiovascular Disease Outcomes and Mortality. Individual Participant Data Meta-Analysis, Development and Validation of a Prognostic Algorithm: The INTERPRESS-IPD Collaboration.”
Systolic and diastolic blood pressures are important risk factors for occurrence and recurrence of stroke1. The latest guideline for management of hypertension recommended to check blood pressure in both arms2, and different result is often found when checked bilaterally. These inter-arm blood pressure differences (IABDs) are reported in general population (4%), diabetic patients (7%) and stroke patients (10%)3,4.
Stroke is one of the leading causes of disability, loss of productivity, and poor functional outcome including mortality5,6. Disability and poor functional outcome from stroke cause serious burden to patients themselves and their caregivers6.
Additionally, recurrent stroke accounts for 10–25% of the total stroke7. Recurrent stroke increases mortality and exacerbates the disability of stroke patients8. Therefore, identifying and modifying factors associated with recurrent stroke are important tasks for treating stroke patients.
IABD can be easily measured at outpatient clinic and can be used as an important indicator or predictor in clinical fields. The major cause of IABD includes atherosclerosis and stenosis due to various diseases in the aorta, subclavian arteries and their branches9.
In stroke patients, considering the relationship between extensive atherosclerosis and poor clinical outcome10, IABD may also have an association with recurrent stroke. However, few studies have reported these issues11.
Our hypothesis is that increased IABD would be related with recurrent stroke in non-cardioembolic stroke patients.
Our study showed that IASBD and/or IADBD ≥10 mmHg was associated with recurrent stroke after adjustment for stroke severity (NIHSS), cerebral atherosclerosis, baPWV, and high-grade white matter hyperintensities, which were closely related factors for stroke.
Thus, our study suggests that IASBD or IADBD, which can be easily measured in a clinical field, may be an independent factor for associating or predicting recurrent stroke in non-cardioembolic stroke patients.
Our study demonstrated that IASBD and/or IADBD ≥10 mmHg was associated with recurrent stroke after non-cardioembolic stroke. Previous studies reported that IABD is related with vascular death and all-cause mortality12, and these results were consistently noted in populations without known cardiovascular disease13 and in chronic kidney disease patients14.
In elderly patients with hypertension, IASBD ≥10 mmHg was an independent risk factor for increasing the risk of cardiovascular disease and mortality15. In contrast, the Framingham Heart Study reported no significant relationship with IABD and mortality16. However, up to now, preceding studies regarding IABD and recurrent stroke are rare.
In a previous study of patients with acute ischemic stroke, IASBD and/or IADBD ≥10 mmHg was associated with long-term mortality11. In patients with non-cardioembolic stroke, cerebral artery stenosis, which is a major predictor for poor prognosis after stroke, was diversely associated with IABD4. Another study showed low ABI was associated with recurrent stroke in patients with acute cerebral infarction17.
Our study supports these findings and may give additive information for the associations of IABD and stroke recurrence. Moreover, bi-brachial blood pressure measurements might play a role as a screening tool for stroke patients to estimate the possibility of recurrent stroke in non-cardioembolic stroke patients.
Our study demonstrated that large artery atherosclerosis stroke subtype was more frequently noted in the IASBD ≥10 mmHg group than in the IASBD <10 mmHg group for the stroke subtype of recurrent stroke. These results are consistent with previous findings that IABD is associated with cerebral atherosclerosis4, which is an important risk factor for ischemic stroke occurrence or recurrence.
Another study also revealed association of arterial stiffness index and large artery atherosclerosis stroke subtype18, and the results of previous studies in which large artery atherosclerosis was associated with asymptomatic lacunar infarction19. Meanwhile, hemorrhagic stroke subtype was less frequently noted in the IASBD ≥10 mmHg group than in those with IASBD <10 mmHg.
In contrast to our results, previous studies have revealed large artery atherosclerosis, such as aortic atheroma, was significantly associated with cerebral microbleeds that act as imaging biomarkers for future cerebral haemorrhage19,20. These results suggest that a large IABD causes cerebral hypoperfusion in the brain, resulting in an ischemic prone state rather than a hemorrhagic prone state, but further research is needed.
Several hypotheses may explain the relationship of IABD with recurrent stroke. IABD is related with advanced atherosclerotic disease in the aorta and its large branches9, which may cause an insufficient cerebral blood flow21. The hemodynamic dysfunction may be a part of the cause of recurrent stroke or poor clinical outcome22.
Furthermore, larger atherosclerotic burden is correlated with early poor clinical outcome in stroke population10. In addition, previous study discovered that IABD resulting from one-arm ischemia in hypertensive or normotensive patients was related with flow-mediated dilatation23, which represents endothelial dysfunction.
Increased arterial stiffness may be a link for our study. Arterial stiffness is associated with worse outcome in patients with acute cerebral infarction24,25,26. A population-based study showed large IABD was related with arterial stiffness, which is in line with our study27.
There are some limitations in our research. First, although consecutive patients were included in this study, the possibility of selection bias exists because of the retrospective study design. Second, it is difficult to generalize our findings to another population or cohort considering that our study population is limited to a single comprehensive center.
Third, multiple, automatic, and simultaneous assessments are recommended for accurate IABD measurements rather than a single, manual, and sequential evaluation methods. We used an automatic and simultaneous measurement device; however, IABD was investigated only once during the ABI assessment and additional follow up data was lacking.
In conclusion, our results demonstrated that IASBD ≥10 mmHg and/or IADBD ≥10 mmHg is associated with recurrent stroke. An IABD ≥10 mmHg could be a useful indicator of risk of recurrent stroke in non-cardioembolic stroke patients.
reference link: https://www.nature.com/articles/s41598-019-49294-8
More information: Hypertension (2020). DOI: 10.1161/HYPERTENSIONAHA.120.15997