Relationship of visit-to-visit and ambulatory blood pressure variability to vascular function in African Americans

Abstract

BACKGROUND Visit-to-visit clinic blood pressure variability (BPV) and 24-hour BPV have both been identified as independent risk factors for cardiovascular (CV) morbidity and mortality; however the mechanisms contributing to the increased CV risk as yet are unclear. The purpose of this study was to assess the relationship between BPV and endothelial function in a cohort of putatively healthy African Americans. METHODS 36 African Americans who were sedentary, non-diabetic, non-smoking, free of cardiovascular and renal disease and not on antihypertensive medication followed an American Heart Association low fat, low salt diet for 6 weeks. Upon completion of the 6-week dietary stabilization period, participants underwent 24-hour ambulatory BP monitoring and had their office BP measured on three separate days. Right brachial artery diameter was assessed at rest, during reactive hyperemia (flow-mediated dilation: FMD), and after nitroglycerin administration (nitroglycerin-mediated dilation: NMD). RESULTS Participants classified as having decreased endothelial function according to either %FMD or the FMD/NMD ratio had significantly higher 24-hour BPV and a trend for higher visit-to-visit BPV when compared to participants with normal endothelial function. Continuous variable analyses revealed a significant positive association between NMD and 24-hour diastolic BPV (DBPV). Visit-to-visit systolic BPV (SBPV), 24-hour SBPV, and 24-hour DBPV were all negatively associated with the FMD/NMD ratio. All relationships remained significant after adjustment for age, BMI, and mean BP levels. CONCLUSIONS These results may suggest that BPV is in increased in African Americans with decreased endothelial function and is associated with the vascular smooth muscle response to nitric oxide.

The relationships between visit-to-visit blood pressure variability and renal and endothelial function in chronic kidney disease

“…It is therefore generally thought that NMD depends mainly on nitroglycerin-induced smooth muscle function, and that the contribution of endothelial function is almost negligible. In a study of 36 African Americans, Diaz et al 13 showed that higher visit-to-visit BPV (SD SBP and CV SBP) was associated with a lower FMD/NMD ratio, independent of age, body mass index and mean BP levels. Our finding of a significant negative association between visitto-visit BPV and FMD (Table 4) in Japanese patients was in accordance with their study, although this is the first report to show an association between visit-to-visit BPV and endothelial dysfunction in CKD patients.…”

“…10 Endothelial dysfunction is considered to be the initial pathogenic event of atherosclerosis and is a risk factor for cardiovascular disease. 11,12 Keith et al 13 showed that higher visit-tovisit BPV was associated with endothelial dysfunction in African Americans, and suggested that endothelial dysfunction may be the link between visit-to-visit BPV and atherosclerosis.…”

Characteristics of blood pressure profiles and vascular dysfunction

“…On the basis of the results obtained in this paper, Diaz et al 7 suggest that blood pressure variance is a more important predictor of cardiovascular diseases than office or home blood pressure, although their cross-sectional study shows only the relationship between vascular function and blood pressure variance and does not show a direct cause-and-effect relation between high blood pressure and cardiovascular events. Additionally, in this study, a single 0.4 mg dose of a sublingual nitroglycerin tablet was given to assess NMD, an endothelium-independent vasodilation measure.…”

“…Guyton described how this latter factor contributes the most to controlling blood pressure after the arterial pressure suddenly becomes abnormal. 6 In this issue of the Journal, Diaz et al 7 estimated blood pressure, including visit-to visit and ambulatory blood pressure variability, office blood pressure and 24-hour blood pressure, in nonmedicated African Americans after a low-fat, low-salt diet and compared the values with flow-mediated vasodilation (FMD), nitroglycerin-mediated dilatation (NMD) and their ratio. They concluded that an increase in blood pressure variation, such as visit-to-visit systolic blood pressure variability, 24-hour systolic blood pressure variability and 24-hour diastolic blood pressure variability, is associated with reduced endothelial function as well as reduced vascular smooth muscle function.…”

“…Differences in blood pressure assessments should receive more attention so that clinicians can take into account differences in measurement procedures and environmental conditions. An approach such as that described by Diaz et al 7 using ambulatory blood pressure monitoring can provide information on which is the best assessment of blood pressure, allowing researchers to refine the risk stratification for cardiovascular disease in patients with hypertension. The results obtained in these studies are sure to be reflected in future guidelines for the management of hypertension.…”