Blood pressure time at target and its prognostic value for cardiovascular outcomes: a scoping review

Abstract

The proportion of time that blood pressure (BP) readings are at treatment target levels, commonly referred to as time at target or time in therapeutic range (BP-TTR), is emerging as a useful measure for evaluating hypertension management effectiveness and assessing longitudinal BP control. However, method of determination for BP-TTR differs across studies. This review identifies variations in BP-TTR determination methodologies and its potential prognostic value for cardiovascular outcomes. Following PRISMA extension for scoping reviews guidelines, literature was systematically searched in Embase, PubMed, Scopus, Web of Science, and CINAHL. Relevant clinical trials, observational studies, cohort studies, cross-sectional studies, and systematic reviews published in English were screened. Of 369 articles identified, 17 articles were included. Studies differed in the BP targets used (e.g., BP < 140/90 mmHg or 130/80 mmHg; systolic BP within 110-130 mmHg or 120-140 mmHg), BP-TTR measurement duration (range 24 h to 15 years), and calculation method (linear interpolation method, n = 12 [71%]; proportion of BP readings at target, n = 5 [29%]). Regardless of method, studies consistently demonstrated that higher BP-TTR was associated with reduced risk of cardiovascular outcomes. Six of eight studies found the association was independent of mean achieved BP or last measured BP. Despite variation in methods of BP-TTR determination, these studies demonstrated the potential prognostic value of BP-TTR for cardiovascular outcomes beyond current BP control measures. We recommend standardization of BP-TTR methodology, with preference for linear interpolation method when BP measurements are few or less frequent, and proportion of BP readings method when large number of BP readings are available.

Keywords: Blood pressure; Blood pressure variability; Hypertension; Time at target; Time in therapeutic range.

Fig. 1

Flowchart representing the selection of sources of evidence

Fig. 2

Schematic representation of the two methods for determining BP-TTR. In this schematic representation, the time duration over which BP-TTR is determined is 14 days and BP target level is systolic BP < 130 mmHg, or systolic BP within 110–130 mmHg. All four figures show the same data. The left (A, B), represents the linear interpolation method, which assumes a linear change between two consecutive BP measurements (i.e., BP changes the same amount with each unit change in time; closed circles) and BP between the consecutive measurements are interpolated (open squares). BP-TTR is determined as the proportion of time BP was (A) below the target level, or (B) within the target range, i.e., the number of days BP was in range divided by the total number of days over which BP-TTR is determined. The right (C, D), represents the proportion of BP readings method. BP-TTR is determined as the proportion of BP readings (C) below the target level, or (D) within the target range (bottom graph), i.e., the number of BP readings in range divided by the total number of BP readings within the duration over which BP-TTR is determined