Having a systolic blood pressure (SBP) difference of 15 mm Hg or more could be a good indicator of risk for vascular disease and death, according to a study published online Jan. 30 on the Lancet. During the meta-analysis, researchers from the U.K. assessed whether there was linkage between differences in SBP and peripheral vascular disease, as previous studies have shown that these types of differences show a poorer prognosis.
To do so, Christopher E. Clark, MD, of the Peninsula College of Medicine and Dentistry, University of Exeter in Exeter, England, and colleagues combed data from various databases and identified 20 studies for review that included studies published prior to July 2011 and showed differences in systolic blood pressures arms.
Clark et al reported estimates of the association between differences in systolic blood pressures between each arms and outcomes for subclavian stenosis, peripheral vascular disease, cerebrovascular disease, cardiovascular disease or survival.
The authors found a mean difference in systolic blood pressure of 36.9 percent for subclavian stenosis with a 50 percent or more occlusion in five invasive studies. Additionally, the difference of 10 mm Hg was found to be more strongly associated with subclavian stenosis. Within the non-invasive studies, Clark et al reported that a difference of 15 mm Hg or more was linked to peripheral vascular disease. Additionally, the difference of 15 mm Hg had a greater associated with pre-existing cerebrovascular disease, increased cardiovascular mortality and all-cause mortality.
A SBP difference of 10 mm Hg was greater associated with peripheral vascular disease in five studies. While the authors identified no studies that showed a difference in systolic blood pressure between arms associated with angiographically proven peripheral vascular disease in the leg, nine non-invasive studies showed a difference of 15 mm Hg or more was linked to peripheral vascular disease in the leg. This was defined by a measurement of ankle-brachial pressure index that was less than 0.9 or a history of peripheral vascular disease.
In contrast, the authors noted that National Institute for Health and Clinical Excellence (NICE) guidelines for hypertension outline that a difference of less than 10 mm Hg systolic blood pressure should be considered normal. However, the guidelines called a difference of more than 20 mm Hg between study arms “unusual,” and said that this usually occurs in less than 4 percent of people and it typically associated with underlying vascular disease.
“Reduced ankle-brachial pressure indices are strongly correlated with angiographic evidence of large-vessel disease in the leg,” the authors noted. “Our findings strengthen the hypothesis that a difference is due to peripheral vascular disease, and thus might represent a sign of clinical importance; the association of a difference of 15 mm Hg or more with angiographic evidence of carotid or aortic arch disease further supports this notion.”
While the authors said that they did not find an association of coronary artery disease with a difference in SBP, there was an association between increased CV and all-cause mortality. Clark et al said that this showed that a difference does indicate a raised CV risk.
“What constitutes a clinically important difference in SBP between arms is unclear,” the authors wrote. But, Clark et al said that there was an association between the difference and an increased likelihood of peripheral vascular disease and differences in survival.
“Guidelines continue to describe a difference of 10 mm Hg or more as rare, yet our own studies have suggested that prevalence ranges from 10 percent in diabetic patients to 20 percent in general and hypertensive populations,” the authors wrote.
Clark et al concluded that the study findings should be included into future hypertension guidelines to promote screening for peripheral vascular disease and risk factor management.