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Systolic BP Time in Target Range and CV Outcomes
Quick Takes
- This study aimed to find an association between the time SBP was in target range (TTR) and MACE among adults with hypertension.
- A greater TTR for SBP was associated with a decrease in MACE, independent of traditional CV risk factors and even after adjusting for mean SBP and SBP variability.
- This suggests an incremental value of TTR beyond other SBP metrics.
Study Questions:
For adults with hypertension, what is the association between time in systolic blood pressure (SBP) target range and major adverse cardiac events (MACE), independent of mean SBP and SBP variability?
Methods:
This was a post hoc analysis of SPRINT (Systolic Blood Pressure Intervention Trial), an open-label, randomized, controlled study comparing intensive (<120 mm Hg) to standard (<140 mm Hg) SBP treatment in adults with hypertension and high cardiovascular (CV) risk. In this study, for the intensive and standard groups, systolic target range was 110-130 mm Hg and 120-140 mm Hg, respectively. In the original trial, BP was measured at monthly intervals for the first 3 months, then every 3 months unless target BP had not yet been achieved, or medication intensification occurred. CV outcomes included individual MACE components, and treatment-related serious adverse events. In his manuscript, the authors add a new metric, time in target range (TTR), which is estimated based on linear interpolation (essentially, connecting the dots between BP measurements). They then examine associations between TTR and major CV events using adjusted Cox proportional hazards regression models and compare them to standard metrics (mean SBP and SBP variability).
Results:
The final cohort data consisted of 6,162 participants with a mean age of 68 ± 10 years, 38% were women, and 17% had a history of CV disease. The overall median TTR for SBP was 47% (interquartile range [IQR], 18%-72%) for the intensive group and 51% (IQR, 25%-75%) for the standard group (likely reflecting the more stringent target range of the former). Participants with >75% TTR were younger, had lower 10-year CV risk, and lower baseline SBP, as compared to participants with <25% TTR (p < 0.001 for all). The primary outcome of first MACE occurred in 356 patients over a median follow-up of 3.3 years. Each one-standard deviation increase in TTR was significantly associated with a decreased risk of first MACE (hazard ratio [HR], 0.78; 95% confidence interval [CI], 0.7-0.87; p < 0.001). The association persisted after adjustment for age, sex, and race (HR, 0.78; 95% CI, 0.7-0.87; p < 0.001) and even after full adjustment for demographics, medical history, and baseline SBP (HR, 0.78; 95% CI, 0.73-0.91; p < 0.001). TTR performed superiorly to related measurements, including mean SBP and SBP variability, which were not significantly associated in fully adjusted models with first major CV event or the individual components of this composite outcome. Indeed, TTR was associated with MACE even after adjustment for mean SBP or SBP variability (HR, 0.85; 95% CI, 0.74-0.96; p = 0.011).
Conclusions:
In adults with hypertension and high CV risk, greater TTR for SBP was associated with a decrease in MACE, independent of traditional CV risk factors and even after adjusting for mean SBP and SBP variability. This suggests an incremental value of TTR beyond other SBP metrics.
Perspective:
Hypertension is the leading risk factor for CV disease and premature death in the world. However, BP remains suboptimal despite decades of guidelines, public awareness campaigns, and a multitude of new medications. Furthermore, standard BP control metrics may not capture BP fluctuations over time. Some recent work has focused on the reliability of BPs obtained in various settings (office vs. home vs. dedicated 24-hour ambulatory BP monitoring) and its association with left ventricular mass. Interestingly, this suggested that 1 week of home BP measurements was the most reliable. In this post hoc analysis of a subcohort in the SPRINT study, a novel metric for BP monitoring was introduced. At first glance, it is hard to imagine that a metric based on linear interpolation of discrete SBP measurements made months apart would have much predictive value. The data are fairly compelling, however, and suggest that this simple calculation may outperform related metrics like mean SBP or even SBP variability, as these may fail to capture the full spectrum of hypertension-related CV risk. TTR provides incremental value beyond the mean SBP, and the authors suggest it could become a metric for population-level quality monitoring and clinical trials of BP interventions. However, prospective studies will be needed to validate the TTR in a larger, more general population of patients not enrolled in BP management trials.
Clinical Topics: Geriatric Cardiology, Heart Failure and Cardiomyopathies, Prevention, Hypertension
Keywords: Antihypertensive Agents, Blood Pressure, Blood Pressure Monitoring, Ambulatory, Blood Pressure Determination, Geriatrics, Hypertension, Mortality, Premature, Primary Prevention, Quality Control, Reproducibility of Results, Risk Factors, Systole
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