When Two is Better Than One

Abstract & Commentary

By Rahul Gupta, MD, MPH, FACP
Clinical Assistant Professor, West Virginia University School of Medicine, Charleston, WV

Dr. Gupta reports no financial relationships relevant to this field of study.

Synopsis: A community-based cohort study finds that systolic blood pressure difference between both arms is common and associated with a significant increased risk for future cardiovascular events.

Source: Weinberg I, et al. The systolic blood pressure difference between arms and cardiovascular disease in the Framingham Heart Study.
Am J Med 2014;127:209-215.

Blood pressure (bp) recordings often differ between arms, but the extent to which these differences exist is significant. Generally, an increased interarm systolic BP difference is usually defined as 10 mmHg or greater, and evidence suggests that 20% of people may have this finding.1 Some experts suggest that bilateral BP measurements should become a routine part of cardiovascular assessment in primary care since significant differences in systolic BP between arms may be able to predict an increased risk of cardiovascular events and all-cause mortality over time in people with hypertension.² Therefore, this difference could be a valuable indicator of increased cardiovascular risk and may become central to appropriate identification and treatment of hypertension. While an association between the interarm systolic BP differences in individuals and mortality has been noted in some studies, the direct association with cardiovascular disease remains to be better defined.

In their research, Weinberg et al describe the distribution of interarm systolic BP difference and risk factor correlates as well as examine the association between interarm systolic BP difference and incident cardiovascular disease and all-cause mortality.

Using data from the Framingham Heart Study cohorts, the researchers evaluated interarm systolic BPs of 3390 patients (56.3% female) aged ≥ 40 years (mean age 61.1 years) who had no history of cardiovascular disease and who were examined as part of the original study cohort (between 1991 and 1994) and an offspring cohort (between 1995 and 1998). An increased interarm pressure difference was defined as ≥ 10 mmHg. The maximal difference between arms was used and patients were followed through 2010.

Researchers found that the mean absolute interarm systolic BP difference was 4.6 mmHg. During the follow-up period, a first cardiovascular event occurred in 598 (17.6%) study subjects. Of these subjects, 26.2% had an interarm systolic BP difference of > 10 mmHg. Researchers also found that compared with participants who had a normal interarm pressure difference, those with elevated differences tended to be older (63 years vs 60.9 years), and to have higher rates of diabetes mellitus (13.3% vs 7.5%), higher systolic BP (136.3 mmHg vs 129.3 mmHg), and higher total cholesterol levels (212.1 mg/dL vs 206.5 mg/dL).

After adjusting for cardiovascular risk factors, an interarm BP difference was associated with a significantly higher risk of first-time cardiovascular events (hazard ratio [HR] 1.38; 95% confidence interval [CI], 1.09-1.75). For every standard deviation increase in interarm systolic BP difference, the HR was 1.07 (95% CI, 1.00-1.14). An association between interarm pressure difference and mortality risk was not found.

Weinberg et al conclude that the increased interarm systolic BP difference that was found to be present in nearly 10% of individuals in the study is not only associated with increased levels of traditional cardiovascular risk factors but also an increased risk for incident cardiovascular events, independent of traditional cardiovascular risk factors.

COMMENTARY

Accurate measurement of BP is important for detection, evaluation, and treatment of hypertension. With heart disease continuing to be one of the leading causes of death in the United States, there is a constant search for simple and practical tools physicians can use in practice to identify those at higher risk for adverse events within a cohort of hypertensive patients. While accurate measurement and interpretation is essential for proper diagnosis and management of hypertension, current guidelines recommend that BP should be assessed in both arms at the initial visit and the arm with the higher value should be used for assessment at subsequent visits.³ However, the current study reaffirms that interarm systolic BP differences are fairly common. Moreover, the research finds that such individuals are at an increased risk for incident cardiovascular events, independent of traditional risk factors. These findings are consistent with previous evidence that has found a relationship between interarm systolic BP difference and subclavian artery stenosis, which has been linked to an increased risk of cardiovascular events. According to these findings, it probably makes sense for physicians to consider including BP readings in both arms to get the most accurate readings possible and detect any differences in BP at each visit. The interarm systolic BP difference can easily serve as a simple clinical indicator of increased cardiovascular risk, and the ensuing treatment and monitoring of those patients may be followed more closely. The best part is that this clinical practice tool is not only useful but also inexpensive.

References

1. Clark CE, et al. Prevalence and clinical implications of the inter-arm blood pressure difference: A systematic review. J Hum Hypertens 2006;20:923-931.
2. Clark CE, et al. The difference in blood pressure readings between arms and survival: Primary care cohort study. BMJ 2012;20:344:e1327.
3. Pickering TG, et al. Recommendations for Blood Pressure Measurement in Humans: An AHA Scientific Statement from the Council on High Blood Pressure Research Professional and Public Education Subcommittee. J Clin Hypertens (Greenwich) 2005;7:102-109.