Supine blood pressure-A clinically relevant determinant of vascular target organ damage in hypertensive patients

Abstract

Night-time blood pressure (BP) is an important predictor of cardiovascular outcomes. Its assessment, however, remains challenging due to limited accessibility to ambulatory BP devices in many settings, costs, and other factors. We hypothesized that BP measured in a supine position during daytime may perform similarly to night-time BP when modeling their association with vascular hypertension-mediated organ damage (HMOD). Data from 165 hypertensive patients were used who as part of their routine clinic workup had a series of standardized BP measurements including seated attended office, seated and supine unattended office, and ambulatory BP monitoring. HMOD was determined by assessment of kidney function and pulse wave velocity. Correlation analysis was carried out, and univariate and multivariate models were fitted to assess the extent of shared variance between the BP modalities and their individual and shared contribution to HMOD variables. Of all standard non-24-hour systolic BP assessments, supine systolic BP shared the highest degree of variance with systolic night-time BP. In univariate analysis, both systolic supine and night-time BP were strong determinants of HMOD variables. In multivariate models, supine BP outperformed night-time BP as the most significant determinant of HMOD. These findings indicate that supine BP may not only be a clinically useful surrogate for night-time BP when ambulatory BP monitoring is not available, but also highlights the possibility that unattended supine BP may be more closely related to HMOD than other BP measurement modalities, a proposition that requires further investigations in prospective studies.

Keywords: hypertension-mediated organ damage; kidney function; nocturnal blood pressure; pulse wave velocity; supine blood pressure.

Figure 1

Color map of the Pearson correlation matrix between various systolic blood pressure entities. The R² values are reported representing the proportion of variance explained by the association between the variables. In the upper right part of the graph, red color in increasing intensity represents moderate to strong correlations. Blue colors in increasing intensity represent small to no shared variance. In the center diagonal and lower left part of the graph, green color and absolute numbers indicate the quantity of cases included in the corresponding correlation. ABPM, Ambulatory Blood Pressure Monitoring; A, Attended; BP, Blood Pressure; UA, Unattended

Figure 2

Scatterplots of the univariate linear regression models (fitted) of supine BP (A) and night‐time systolic ABPM BP (B) as independent variables and PWV as a dependent variable. The orange crosses represent the predicted values of the linear model forming the line of best fit. Beige dots represent the mean (inner line) and observed (outer line) 95% confidence intervals of these predictions. The multivariate linear regression model is shown in panels C (supine BP on x‐axis) and D. Models were fitted using ordinary least squares. PWV—Pulse Wave Velocity, Sys—Systolic, SBP—systolic blood pressure, ABPM—Ambulatory Blood Pressure Monitoring

Figure 3

Receiver operating curves (ROC) for logistic regression models predicting systolic night‐time hypertension (cutoff 120 mmHg) as a binary dependent variable with day‐time blood pressure measurements (cutoff 140 mmHg) as independent, continuous variables. Fitting the model with supine blood pressure yielded the highest area under the curve (0.78), indicating a stronger association with night‐time blood pressure