Differences in blood pressure between a person's left and right arm could indicate that the patient has vascular disease and is at increased risk of death. These are among the findings in a systematic review and meta-analysis published Online First by The Lancet, written by Dr Christopher E Clark, Peninsula College of Medicine and Dentistry, University of Exeter, Devon, UK, and colleagues. The authors say the findings mean that measurement of blood pressure in both arms should be part of routine care.
The study reviewed 28 papers covering difference in systolic blood pressure between arms. It found significant evidence to suggest that a difference of 15mm Hg or more was associated with increased risk of: peripheral vascular disease (PVD: the narrowing and hardening of the arteries that supply blood to the legs and feet: 2.5 times increased risk); pre-existing cerebrovascular disease (affecting the blood supply to the brain and often associated with cognitive issues such as vascular dementia: 1.6 times increased risk); and both cardiovascular mortality (70% increased risk), and all-cause mortality (60% increased risk). The risk of PVD was also increased at a difference of 10mm Hg or more. The arm with the higher pressure can vary between individuals and it is the difference that counts, not which arm is higher and which is lower.
The authors note that early detection of PVD is important because interventions to promote smoking cessation, lower blood pressure, or offer statin therapy can reduce mortality. Most cases, however, are clinically silent, and gold-standard non-invasive identification of this disease requires detection of a reduced ankle-brachial pressure index (ratio of BP in ankle to BP in arm) at rest or after a stress test. This complex technique requires time, experience, and training; it is not routinely undertaken in primary-care assessment of hypertensive patients and is not proposed within the UK vascular check programme. Thus the findings of this new study further support the need for both-arm blood pressure checks to be the norm. Dr Clark says that the research team will be flagging its findings to the UK Vascular Check programme.
The authors conclude: "Our findings suggest that a difference in SBP of 10 mm Hg or more or 15 mm Hg or more between arms could identify patients at high risk of asymptomatic peripheral vascular disease and mortality who might benefit from further assessment. Findings from our study should be incorporated into future guidelines for hypertension and blood-pressure measurement to justify bilateral brachial measurement in the assessment of individuals, and to promote targeted screening for peripheral vascular disease and aggressive risk factor management in subjects with a demonstrable systolic between-arm difference."
In a linked Comment, Professor Richard J McManus, Department of Primary Care Health Sciences, University of Oxford, UK and Professor Jonathan Mant, Department of Public Health and Primary Care, University of Cambridge, UK say: "Further research is needed to clarify whether substantial differences between arms should prompt aggressive management of cardiovascular risk factors. Overall, Clark and colleagues' systematic review and meta-analysis supports existing guidelines stating that blood pressure should be measured in both arms. Ascertainment of differences should become part of routine care, as opposed to a guideline recommendation that is mostly ignored."
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