Don't ignore diastolic blood pressure values, say researchers

By Dr. Ananya Mandal, MDJul 18 2019

A large study from clinicians at Kaiser Permanente has concluded that both the upper and lower values of blood pressure readings (systolic and diastolic blood pressure) are associated with the risk of heart attack and stroke. The new study, which is titled “Effect of Systolic and Diastolic Blood Pressure on Cardiovascular Outcomes,” appeared in the latest issue of the New England Journal of Medicine, this week.

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Previously, clinicians believed that heart attack and stroke risk is intimately tied with the upper number of the blood pressure, known as systolic blood pressure. This new NEJM study counters this hypothesis saying that both systolic and diastolic blood pressures are equally harmful.

This research brings a large amount of data to bear on a basic question, and it gives such a clear answer. Every way you slice the data, the systolic and diastolic pressures are both important.”

Dr. Alexander C. Flint, Stroke Specialist

Systolic blood pressure is the pressure exerted on the walls of the arteries when the heart pumps out blood. On the other hand, diastolic blood pressure (the lower number) refers to the residual pressure on the arterial walls when the heart is at rest (between beats).

Recommended blood pressure levels are 120/80 mm Hg and high blood pressure is defined as any measures over 140/90 mm Hg, where 140 mm is the systolic blood pressure and 90 mm is the diastolic pressure. However, in some cases, a reading of 130/80 mm of Hg is considered high enough for medical treatment.

Re-writing the guidelines

Earlier studies have shown that high systolic blood pressure results in adverse outcomes of the heart and thus the treatment guidelines for hypertension or high blood pressure have focussed on reducing the systolic blood pressure.

The study, which was the largest of its kind, included 36 million blood pressure readings that were recorded in the outpatient visits between 2007 and 2016.

In total, the study included 1.3 million adults living in Northern California. The team looked at the incidences of “myocardial infarction, ischemic stroke, or hemorrhagic stroke” or heart attack and strokes over a period of 8 years for which the participants were followed up.

The results of the study revealed that systolic blood pressure may have a greater impact on heart attack and stroke but diastolic blood pressure is no less important.

The American College of Cardiology and American Heart Association guidelines have recently recommended that blood pressure control needs to be tighter, with the limit being lowered from 140/90 to 130/80 mm of Hg. This recommendation only applies to people with a high risk of complications, such as a family history of heart problems.

The results from the new study provide evidence to suggest that both systolic and diastolic blood pressure values are important and need to be controlled to prevent heart disease and related events. The results were also in accordance with the National Institutes of Health's Systolic Blood Pressure Intervention Trial, known as SPRINT.

The recent European guidelines for the definition of hypertension remains 140/90 mm whereas the American Guidelines are pressure above 130/80mm. The American guidelines are based on the SPRINT (Systolic Blood Pressure Intervention Trial).

Controversy has long persisted about whether systolic blood pressure, diastolic blood pressure, or both contribute to cardiovascular risk. This analysis using a very large amount of longitudinal data convincingly demonstrates that both are important, and it shows that in people who are otherwise generally healthy, lower blood pressure numbers are better.”

Dr. Deepak L. Bhatt, Senior Author & Director of Interventional Cardiovascular Services at Brigham and Women's Hospital

The authors of the study concluded, “Although systolic blood-pressure elevation had a greater effect on outcomes, both systolic and diastolic hypertension independently influenced the risk of adverse cardiovascular events, regardless of the definition of hypertension (≥140/90 mm Hg or ≥130/80 mm Hg).”

This study was financially supported by the Kaiser Permanente Northern California Community Benefit Program.