BP Difference Between Arms Correlates with Vascular Disease and Mortality

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BP Difference Between Arms Correlates with Vascular Disease and Mortality

A meta-analysis found significant associations, although the test’s sensitivity was low.

Peripheral vascular disease (PVD) is usually asymptomatic. It can be detected noninvasively using the ankle-brachial index, but differences in systolic blood pressure (SBP) between arms also can reflect PVD. Some guidelines recommend checking pressure in both arms, but few clinicians do so regularly.

To determine the diagnostic and predictive value of a difference in SBP between arms, British investigators conducted a meta-analysis of 20 studies in which between-arm SBP difference was correlated with historical or concomitant vascular disease (detected invasively or noninvasively) or future mortality. In studies using angiography, a between-arm SBP difference of ≥10 mm Hg was strongly associated with concomitant subclavian stenosis (risk ratio, 8.8). In noninvasive studies, a difference of ≥15 mm Hg was significantly associated with PVD (RR, 2.5; sensitivity, 15%; specificity, 96%), preexisting cerebrovascular disease (RR, 1.6; sensitivity, 8%; specificity, 93%), elevated cardiovascular mortality (hazard ratio, 1.7), and elevated all-cause mortality (HR, 1.6).

The Journal Watch General Medicine Perspective

This report generated media publicity and phone calls from worried patients. Most studies reviewed here enrolled patients already at high risk for vascular disease, although the studies in lower-risk populations produced similar results. A practical barrier to interpretation of between-arm SBP difference is the importance of measurement technique: White-coat effects can yield 15-mm differences when measurement is repeated even in the same arm within a minute or two, and few clinicians can readily achieve the gold standard of repeated simultaneous measurement in two arms. Finally, it’s unclear whether bilateral BP measurement adds independently to risk prediction when adjusted for other risk factors (not done in this analysis), and whether benefits of routine bilateral measurement would outweigh potential harms (for example, from downstream invasive vascular procedures in asymptomatic people).

Bruce Soloway, MD

The Journal Watch Cardiology Perspective

Most of the patients in this analysis were at high risk for vascular disease, and the threshold for a meaningful bilateral SBP difference was deliberately set low; nonetheless, these results suggest that routine assessment of bilateral arm pressure can provide valuable information. Given these initial findings, clinicians may reasonably step up their assessment of bilateral arm pressures, particularly in high-risk patients. Further studies are warranted to determine whether bilateral BP measurement improves diagnosis or outcomes and to better delineate which patients will benefit most from the technique.

JoAnne M. Foody, MD

Clark CE et al. Association of a difference in systolic blood pressure between arms with vascular disease and mortality: A systematic review and meta-analysis. Lancet 2012 Jan 30 ; [e-pub ahead of print]. (http://dx.doi.org/10.1016/S0140-6736(11)61710-8)

McManus RJ and Mant J. Do differences in blood pressure between arms matter? Lancet 2012 Jan 30 ; [e-pub ahead of print]. (http://dx.doi.org/10.1016/S0140-6736(11)61926-0)

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