Date Published: April 10, 2019
Publisher: Public Library of Science
Author(s): Joseph F. Polak, Pamela Ouyang, Dhananjay Vaidya, Giacomo Pucci.
Brachial artery reactivity (BAR) is usually determined as the maximum brachial artery diameter (BAD) following release of an occluding pressure cuff compared to a BAD before cuff inflation. BAD early after cuff deflation can also serve as baseline for estimating total brachial artery reactivity (TBAR). We investigate whether TBAR is associated with first time coronary heart disease events.
Participants of the Multi-Ethnic Study of Atherosclerosis (n = 5499) consisting of whites, African-Americans, Chinese and Hispanics were followed longitudinally for a mean of 12.5 years. Brachial artery ultrasound was performed following five minutes of cuff occlusion at the forearm. TBAR was estimated from BAD following cuff release as the difference between maximum and minimum brachial artery diameters divided by the minimum diameter multiplied by 100%. TBAR was added to multivariable Cox proportional hazards models with Framingham risk factors as predictors and time to first coronary heart disease event as outcome.
Average TBAR was 9.7% (9.7 SD). Mean age was 61.7 years, 50.9% women. Increased TBAR was associated with lower risk of CHD events with a hazard rate of 0.78 per SD increase (95% C.I. 0.67, 0.91; p = 0.001). A TBAR below the median of 7.87% (Inter Quartile Range: 4.16%, 13.0%) was associated with a 31% lower risk of coronary heart disease event (Hazard Ratio: 0.69; 95% C.I.: 0.55, 0.87).
TBAR is an independent predictor of first time coronary heart disease events and is exclusively measured after release of a blood pressure occlusion cuff.
The brachial artery dilates in response to the endogenous release of nitric oxide (NO) that occurs during reactive hyperemia . Brachial artery flow-mediated dilation (FMD), also called brachial artery reactivity (BAR), is typically seen on ultrasound imaging following the release of an occlusive blood pressure cuff that has been kept inflated for five minutes in order to induce forearm ischemia. An increase in brachial artery diameter is a marker of an “healthy endothelium” while lessened degrees of diameter increase are associated with increased risk of cardiovascular outcomes . The calculation of BAR typically relies on obtaining a baseline diameter before cuff inflation  and is ideally done with the aid of a stereotactic device that stabilizes the location of the ultrasound imaging probe over the brachial artery [1, 4].
We have measured total brachial artery reactivity (TBAR) by relying on the brachial artery diameters obtained following the release of a blood pressure occlusion cuff. We have shown that this measurement is an independent predictor of future coronary heart disease events in a population free of cardiovascular disease at baseline after accounting for the Framingham risk factors.