Cardiovascular Outcomes May Inform Systolic and Diastolic BP Targets

The cardiovascular (CV) risk patterns of systolic blood pressure (SBP) and diastolic blood pressure (DBP) measurements differ by clinical outcomes, and determining a patient’s ideal blood pressure (BP) targets may depend on the CV event for which they are most at risk, according to findings published in the Journal of the American College of Cardiology.

In the United States, current guidelines for target BP recommend lower than 130/80 mm Hg for nearly all patients. However, these guidelines are largely based on studies that evaluated SBP and DBP independently. Patient risk assessment can be improved by simultaneously combining both BP components as described by the Multiple Risk Factor Intervention Trial and the reanalysis of the Framingham Heart Study.

For the current study, researchers used data from the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT) (ClinicalTrials.gov Identifier: NCT00000542) to evaluate risk patterns for CV events and all-cause mortality associated with SBP and DBP simultaneously.

The primary composite outcome was the simultaneous impact of SBP and DBP on the associated risk for all-cause mortality, congestive heart failure (CHF), myocardial infarction (MI), or stroke. ALLHAT randomly assigned adults to amlodipine, chlorthalidone, or lisinopril and used proportional hazards regression to evaluate the simultaneous association of repeated SBP/DBP measurements on the primary composite outcome as well as each outcome alone.

For the current study, researchers enrolled 33,357 participants with 458,079 total BP measurements (median: 14 per participant, interquartile range [IQR] 11-18). During the median 4.4 years (IQR 3.6-5.4 years) participants were followed, 24.4% experienced 1 or more of the endpoints within the primary composite outcome. When SBP and DBP were simultaneously evaluated, researchers found differing risk patterns depending upon the outcome.

For the primary composite outcome of all-cause mortality and CHF, the researchers reported a U-shaped association with SBP/DBP, while the SBP/DBP corresponding to the lowest risk for these individual outcomes differed. For example, 150/70 mm Hg (hazard ratio [HR] 0.79; CI 0.77-0.82) was associated with the lowest HR for all-cause mortality relative to 120/80 mm Hg, compared with 135/75 mm Hg for CHF (cause-specific HR [csHR] 0.86; CI 0.83-0.89).

The lowest levels of risk for MI were near 120/80 mm Hg, with even 125/75 mm Hg being associated with a significantly higher risk (csHR 1.07; CI 1.03-1.06). Conversely, a linear association was observed between BP and stroke, with a higher csHR associated with higher SBP/DBP levels.

In stratified analysis, the lowest risk levels for the primary composite outcome among participants younger than 65 years was at lower SBP levels and similar DBP levels, compared with participants aged 65 years or older (122/82 mm Hg vs 133/78 mm Hg, respectively). Analyses stratified by diabetes mellitus status and sex were qualitatively similar. Sensitivity analyses showed the lowest risk for CV-related death at DBP levels lower than non-CV-related death. Lower risk for MI or CV death and CHF or CV death was also seen at lower DBPs than for MI or CHF alone.

“Our results suggest that BP targets may need to be modified depending on the CV outcome for which the patient is most at risk,” the study authors noted. “For example, for a given person with history of a previous stroke, more aggressive BP lowering may be warranted given the linear association seen, whereas for the person with a history of previous MI, care would need to be taken to avoid excessive DBP lowering.”

The researchers acknowledged that BP targets cannot be based on the current analysis alone, since the study was observational in nature. They also acknowledged the possibility that different measurement methods could result in different optimal BP combinations. Further prospective trials that simultaneously consider the associated impact of SBP/DBP on CV risk are needed.

Reference

Itoga NK, Tawfik DS, Montez-Rath ME, et al. Contributions of systolic and diastolic blood pressures to cardiovascular outcomes in the ALLHAT study. J Am Coll Cardiol. Published online October 18, 2021. doi:10.1016/jacc.2021.08.035