European Primary Care Cardiovascular Society

Independent association of systolic and diastolic hypertension with CV outcomes

Effect of Systolic and Diastolic Blood Pressure on Cardiovascular Outcomes

Literature - Flint AC, Conell C, Ren X, et al. - N Engl J Med 2019;381:243-51. doi: 10.1056/NEJMoa1803180

Introduction and methods

Focus has been on systolic hypertension after the Framingham Heart Study and other studies demonstrated that systolic hypertension is more important as a predictor of CV outcomes [1]. This was reflected in the 2000 clinical advisory statement from the National High Blood Pressure Education Program [2] and the American College of Cardiology (ACC)–American Heart Association (AHA) risk estimation tool [3] does not include diastolic blood pressure (DBP) for determination of CV risk. In contrast to this, clinicians still record and target values for both systolic BP (SBP) and DBP.

The threshold to define hypertension in the 2017 US hypertension guidelines has changed to 130/80 mm Hg [4], whereas in the European guidelines the threshold is still 140/90 mmHg. Lower targets in the new US hypertension guidelines might result in more patients with diastolic hypotension [6,7,9,10], which might be of concern due to a possible J-curve relationship between DBP and adverse outcomes [5-9].

This study examined whether SBP and DBP were independently associated with the risk of adverse CV outcomes. In addition, the effect of the threshold for the definition of hypertension on the association between SBP and DBP with outcomes was assessed, and a possible J-curve relationship between DBP and outcomes was explored.

A retrospective cohort study was conducted analyzing data from outpatients from Kaiser Permanente Northern California (KPNC), a large integrated health care system [11]. During a 2-year baseline period, initial BP measurements and coexisting conditions were recorded and over an 8-year observation period, additional BP measurements were performed and occurence of MI, ischemic stroke or hemorrhagic stroke was documented. A total of 1.3 million study participants were enrolled, who were ≥18 years and had one BP measurement at baseline (Jan 2007-Dec 2008) and ≥2 BP-measurements during the observation period (Jan 2009-Dec 2016). BP was measured using an automated oscillometric BP cuff.

To determine average hypertension burdens above the thresholds defining hypertension (≥140/90 mmHg or ≥130/80 mmHg), measures were zeroed at the threshold for values at or below the threshold and values above the threshold were expressed in mmHg. Therefore, hypertension burdens were continuous variables with zero values for normal or low BP, and values were standardized to z scores (± SDs from the mean).

Main results

Independent association of systolic and diastolic hypertension with CV outcomes

Conclusion

This large retrospective cohort study including people from Northern California demonstrated that both systolic and diastolic hypertension were associated with increased risk for adverse CV outcomes. The association was similar when using threshold defining hypertension as ≥140/90 mmHg or ≥130/80 mmHg. A J-curve relationship between DBP and outcomes was seen, with higher risk in those with lowest and highest DBP values. The higher risk of outcomes in those with lower DBP could partially be explained by age, other covariates and by a greater effect of systolic hypertension.

References

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