Combined effects of office and 24-h blood pressure on aortic stiffness in human hypertension

Abstract

Aortic stiffness, a prognostically adverse marker of arteriosclerosis, is critically dependent on blood pressure (BP). Office BP may not always reflect BP behaviour away from the medical environment, and it is uncertain whether office or out-of-office BP values are stronger determinants of arterial stiffness. Twenty-four-hour BP and carotid-to-femoral pulse wave velocity (PWV)--a direct measure of aortic stiffness--were measured in 539 never-treated hypertensive patients and in 71 normotensive individuals. Sustained hypertensive patients had a higher age and heart-rate-adjusted aortic PWV than normotensive individuals (9.7 ± 2 vs. 8.5 ± 2 m/s, P<0.001), even after further adjustment for office mean pressure as a measure of distending pressure (P=0.018). The higher aortic PWV in white-coat hypertensive patients as compared with normotensive individuals (9.3 ± 2 vs. 8.5 ± 2 m/s, P=0.026) did not hold after adjustment for office mean pressure (P=0.16). To examine the independent effect of office BP on aortic PWV beyond the influence of 24-h BP, patients were classified according to the difference between observed and predicted office systolic BP (the latter determined by regressing 24-h BP on office BP). Despite having comparable 24-h BP values (131/82 vs. 131/84 mmHg), the patients with higher-than-predicted office BP had higher aortic PWV than those with lower-than-predicted office BP (10.1 ± 2 vs. 9.2 ± 2 m/s, P<0.001). Similarly, after regressing office BP on 24-h BP, the group with higher-than-predicted 24-h BP also had higher aortic PWV (9.9 ± 2 vs. 9.5 ± 2 m/s, P<0.05) despite having identical office BP (152/95 vs. 152/96 mmHg). In a multivariate regression model, both 24-h and office mean BP independently predicted aortic PWV. Both office and out-of-office BP are independent predictors of aortic PWV in hypertension. Elevated BP values over the 24 h are associated with increased isobaric aortic stiffness.