Risk Stratification by Cross-Classification of Central and Brachial Systolic Blood Pressure

Abstract

Background: Whether cardiovascular risk is more tightly associated with central (cSBP) than brachial (bSBP) systolic pressure remains debated, because of their close correlation and uncertain thresholds to differentiate cSBP into normotension versus hypertension.

Methods: In a person-level meta-analysis of the International Database of Central Arterial Properties for Risk Stratification (n=5576; 54.1% women; mean age 54.2 years), outcome-driven thresholds for cSBP were determined and whether the cross-classification of cSBP and bSBP improved risk stratification was explored. cSBP was tonometrically estimated from the radial pulse wave using SphygmoCor software.

Results: Over 4.1 years (median), 255 composite cardiovascular end points occurred. In multivariable bootstrapped analyses, cSBP thresholds (in mm Hg) of 110.5 (95% CI, 109.1-111.8), 120.2 (119.4-121.0), 130.0 (129.6-130.3), and 149.5 (148.4-150.5) generated 5-year cardiovascular risks equivalent to the American College of Cardiology/American Heart Association bSBP thresholds of 120, 130, 140, and 160. Applying 120/130 mm Hg as cSBP/bSBP thresholds delineated concordant central and brachial normotension (43.1%) and hypertension (48.2%) versus isolated brachial hypertension (5.0%) and isolated central hypertension (3.7%). With concordant normotension as reference, the multivariable hazard ratios for the cardiovascular end point were 1.30 (95% CI, 0.58-2.94) for isolated brachial hypertension, 2.28 (1.21-4.30) for isolated central hypertension, and 2.02 (1.41-2.91) for concordant hypertension. The increased cardiovascular risk associated with isolated central and concordant hypertension was paralleled by cerebrovascular end points with hazard ratios of 3.71 (1.37-10.06) and 2.60 (1.35-5.00), respectively.

Conclusions: Irrespective of the brachial blood pressure status, central hypertension increased cardiovascular and cerebrovascular risk indicating the importance of controlling central hypertension.

Keywords: brachial blood pressure; cardiovascular risk; central blood pressure; hypertension; mortality; population science.

Figure 1.

Forrest plots showing the risk of the primary composite cardiovascular end point by category. Central (A) and brachial (B) systolic blood pressure (BP) hazard ratios, given with 95% CI, were adjusted for cohort (random effect) and a propensity score that accounted for sex, age, heart rate, body mass index, smoking and drinking status, serum cholesterol, antihypertensive drug treatment by drug class, history of cardiovascular disease, and diabetes. The linear trend across increasing categories of central and brachial BP was significant (P<0.001).

Figure 2.

Cumulative incidence of the primary composite cardiovascular end point by the cross-classification of central and brachial blood pressure categories. Vertical lines denote the SE. Tabulated data are the number of participants at risk by hypertension category at 1-year intervals. The survival functions and P were derived by proportional hazard regression with concordant normotension as the reference group and with cumulative adjustment for cohort, sex and age. The systolic BP thresholds delineating the 4 groups are given in Table 3. HT indicates hypertension; and NT, normotension.