Between-arm differences in systolic blood pressure may indicate increased mortality risk in hypertension

Patients with hypertension who have a between-arm difference of at least 10 mm Hg in systolic blood pressure (SBP) may be at higher risk for cardiovascular events and death, according to a new study.

Researchers in England examined data from 230 patients with hypertension (defined as blood pressure of ≥160/100 mm Hg or ≥140/90 mm Hg with target organ damage, diabetes, or a coronary heart disease risk score ≥15%) at one primary care practice.

The intent of the study was to determine whether a difference in SBP readings between arms could predict long-term survival. Blood pressure measurements were obtained in both arms at three consecutive visits. The study's main outcome measures were cardiovascular events and all-cause mortality over a median of 9.8 years of follow-up. The results were published online March 20 by BMJ.

At study entry, 55 of 230 participants (24%) had a mean interarm SBP difference of at least 10 mm Hg and 21 of 230 (9%) had a difference of at least 15 mm Hg, while 14 of 230 patients (6%) had a mean interarm difference in diastolic blood pressure (DBP) of at least 10 mm Hg. An association was noted between the two mean SBP differences and all-cause mortality (adjusted hazard ratios, 3.6 [95% CI, 2.0 to 6.5] and 3.1 [95% CI, 1.6 to 6.0], respectively).

One hundred eighty-three patients without preexisting cardiovascular disease but with an SBP difference of at least 10 mm Hg or at least 15 mm Hg between arms also had an increased risk for death (adjusted hazard ratio, 2.6 [95% 1.4 to 4.8] and 2.7 [95% CI, 1.3 to 5.4], respectively). A 10-mm Hg interarm difference in DBP had a weak association with increased risk for death or cardiovascular events.

The authors noted that the sequence in which each arm was measured was not randomized, and that their data came from only one practice, among other limitations. However, they concluded that different SBP readings between arms could indicate a long-term risk for death or cardiovascular events in patients with hypertension.

“Assessment of blood pressure in both arms is recommended by guidelines and should become a core component of initial blood pressure measurement in primary care,” they wrote. “Detection of an interarm difference should prompt consideration of further vascular assessment and aggressive management of risk factors.”

An accompanying editorial pointed out that the authors averaged a single set of sequential blood pressure measurements instead of obtaining repeated simultaneous measurements, which could have led to misclassification of patients whose blood pressure was highly variable. This, along with other study limitations, means that the findings are not definitive and need to be replicated, the editorialist wrote. He added that future studies should also compare interarm differences in blood pressure with known predictors of death from cardiovascular disease.

However, the editorialist recommended that clinicians follow current guidelines and measure blood pressure in both arms to detect patients with a difference of at least 10 mm Hg, in whom the positive predictive value for peripheral vascular disease is high.

“A sequential measurement, followed by confirmation with at least two simultaneous measurements using two automatic devices, seems to be a reasonable approach. The optimal number of repeated measurements and monitoring intervals are unknown,” he wrote.