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Follow clinical guidance to measure BP in both arms

Interarm systolic difference ≥5mmHg linked to nearly doubled risk of CVD mortality

Louise Prime

Friday, 15 April 2016

GPs should follow current clinical guidance when initially assessing for hypertension and measure blood pressure in both arms to pick up differences in systolic pressure between the two, shows research from UK primary care. The study*, published today online first in the British Journal of General Practice, found that even in people free of clinically evident cardiovascular disease, systolic interarm differences (IADs) of even as little as 5mmHg were associated with an almost doubled risk of cardiovascular events, including mortality.

Earlier studies had shown that in cohorts with established vascular disease or high cardiovascular risk, systolic interarm differences ≥10 mmHg or ≥15 mmHg were associated with reduced survival. Primary care researchers in Scotland set out to explore this association in people more representative of a general population. They studied a cohort of the ‘aspirin for asymptomatic atherosclerosis’ (AAA) trial, a randomised controlled trial conducted from 1998-2008 for which 3,350 men and women aged 50–75 years living in central Scotland were recruited from a community health registry. Participants, who had a moderately elevated cardiovascular event risk (defined by an ankle-brachial index ≤0.95) but were free of pre-existing clinical cardiovascular disease, had had a single pair of bilateral brachial blood pressure measurements at recruitment, and were then prospectively followed up for 10 years. At baseline, 60% of the 3,350 participants had a systolic IAD ≥5mmHg and 38% had an IAD ≥10mmHg.

The researchers found that – based on this single pair of measurements – an IAD ≥5mmHg was associated with increased risk of both cardiovascular mortality (adjusted hazard ratio [HR] 1.91) and all-cause mortality (HR 1.44). For the subgroup of 764 participants who had hypertension, IADs of ≥5mmHg or ≥10mmHg were associated with both higher cardiovascular mortality (HR 2.63 and HR 2.96 respectively) and all-cause mortality (HR 1.67 and HR 1.63 respectively). However, IADs ≥15mmHg were not associated with survival differences in this population.

The authors pointed out that their findings support current clinical guidance to measure both arms in the initial assessment of patients for high blood pressure, and to confirm any IAD with simultaneous assessment – advice that, they added, is not currently routinely followed, leaving patients perhaps unknowingly under-investigated or under-treated for hypertension if an IAD is not looked for.

They concluded: “This study has shown that the association of IADs with reduced survival observed in populations at high cardiovascular risk can be extended to a population free of clinically evident cardiovascular disease.”

* Clark CE, Taylor RS, Butcher I et al. Inter-arm blood pressure difference and mortality: a cohort study in an asymptomatic primary care population at elevated cardiovascular risk. British Journal of General Practice, published 15 April 2016. DOI: 10.3399/bjgp16X684949

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