Major cardiovascular and cerebrovascular events including heart attack and stroke often occur in individuals without known pre-existing cardiovascular disease. The prevention of such events, including the accurate identification of those at risk, remains a serious public health challenge. Scoring equations to predict those at increased risk have been developed using cardiovascular risk factors, including cigarette smoking, blood pressure, total and high-density lipoprotein cholesterol, and diabetes mellitus, according to background information in the article. The Framingham risk score (FRS) is often considered the reference standard but has limited accuracy, tending to overestimate risk in low-risk populations and underestimate risk in high-risk populations.
Attention has been given to indicators of asymptomatic atherosclerosis, such as coronary artery calcium and the ankle brachial index (ABI), which is the ratio of systolic pressure at the ankle to that in the arm. It “is quick and easy to measure and has been used for many years in vascular practice to confirm the diagnosis and assess the severity of peripheral artery disease in the legs,” the authors write.
Gerry Fowkes, Ph.D., of the University of Edinburgh, Scotland, and colleagues with the Ankle Brachial Index Collaboration, conducted an analysis of data from 16 studies to determine if the ABI provides information on the risk of cardiovascular events and death independently of the FRS and can improve risk prediction. The studies included a total of 24,955 men and 23,339 women who had ABI measured at baseline and were followed up to detect total and cardiovascular mortality.
The researchers found that the 10-year cardiovascular mortality in men with a low ABI (0.90 or less) was 18.7 percent and with normal ABI (1.11 - 1.40) was 4.4 percent, about a four times higher risk of cardiovascular death for men with low ABI. Corresponding mortalities in women were 12.6 percent and 4.1 percent. The risks remained elevated after adjusting for FRS (2.9 for men vs. 3.0 for women). A low ABI (0.90 or less) was associated with approximately twice the 10-year total mortality, cardiovascular mortality, and major coronary event rate compared with the overall rate in each FRS category. Inclusion of the ABI in cardiovascular risk stratification using the FRS would result in reclassification of the risk category and modification of treatment recommendations in approximately 19 percent of men and 36 percent of women.
This article is adapted from the original press release.