Nancy A. Melville

October 23, 2017

SAN DIEGO — Intensive lowering of systolic blood pressure (SBP) to levels below 120 mm Hg does not increase the risk for stroke, even with lower mean arterial pressure, new research shows.

"Our findings suggest clinicians can safely lower systolic blood pressure when treating patients with hypertension without worrying that they will inadvertently cause a stroke through cerebral hypoperfusion by lowering blood pressure too much," first author, Jack Tsao, MD, from the University of Tennessee Health Science Center, told Medscape Medical News.

The findings were presented here at ANA 2017: 142nd Annual Meeting of the American Neurological Association.

Lower Risk for Cardiovascular Disease, Stroke, Death

While clinical recommendations typically call for target SBP below 140 mm Hg in the prevention of stroke and cardiovascular events, efforts to more intensively lower levels to below 120 mm Hg were shown to further reduce fatal cardiovascular events and mortality in the Systolic Blood Pressure Intervention Trial (SPRINT).

However, patients who did achieve SBP below 120 mm Hg in the study showed higher rates of hypotension, which could have led to decreased cerebral perfusion pressure and an increased stroke risk, the authors noted.

To better assess the effects of the lower SBP on the risk for stroke, Dr Tsao and colleagues further evaluated data on 8844 participants in SPRINT, establishing mean arterial pressure (MAP) and pulse pressure (PP) from the patients' SBP and diastolic blood pressure measurements.

The patients' lowest MAP and PP in the follow-up period were used for the analysis. During a median follow-up of 3.26 years, there were 132 stroke cases (1.49%) and 187 syncope cases (2.1%).

The mean minimal MAP was 78.21 mm Hg and the mean minimal PP was 45.10 mm Hg.

Whereas lower MAP and PP were associated with an increased risk for hypotension and syncope, neither was linked to an increased stroke risk.

The stroke risk did increase consistently by about 31% with every 5–mm Hg increase in MAP (adjusted hazard ratio [HR], 1.31) and about 30% with every 5–mm Hg increase in PP (HR, 1.30).

Likewise, the risk in syncope increased by 39% with every 5–mm Hg increase in MAP (HR, 1.14) and by 14% with every 5–mm Hg increase in PP (HR, 1.14).

"We thought we would see an increased stroke risk with low MAP, so we were actually very happy to find that our primary hypothesis — that there would be an increased stroke risk — was not confirmed," Dr Tsao said.

"The key message for practitioners and patients is that lowering systolic blood pressure using medications in the setting of a diagnosis of hypertension will lower the risk for cardiovascular diseases, stroke, and death," he said.

"Aggressive treatment to get systolic blood pressure under 120 mm Hg is a good thing and will not lead to an increased risk of causing harm through stroke from too low of a systolic blood pressure."

In discussion following Dr Tsao's talk, an audience member raised concerns that the study's methods for measuring blood pressures used an algorithm, typically related to heart rate, that ineffectively captures hypotensive patients on an individual basis, hence compromising the clinical applicability of the data.

Valid Measures

Asked to respond, Dr Tsao told Medscape Medical News he is confident that the measures are indeed valid.

"We talked with the company that made the monitors for the SPRINT study and found that the measurement of systolic blood pressure was an actual value while diastolic blood pressure was derived," he said. 

"We also found out that there was a good correlation between manual measurements of both systolic and diastolic blood pressure and the automated system such that systolic and diastolic blood pressure measurements of the system used were within 1 to 3 mm Hg, which is well within an acceptable margin of variance.

"Thus, we believe our approach is valid, that automated blood pressure is the approach used by most medical centers and any therapy uses these measurements to adjust therapy in practice," Dr Tsao said.

He added that the findings were further validated with additional data.

"Even with the small margin of variance, we did not find higher stroke risk at the lower MAP measurements, and [this was] validated with a second data set (which was not presented) where blood pressure was manually measured."

As reported by Medscape Medical News, another study, published in August in JAMA Neurology, which also used data from SPRINT, showed that target SBP of 120 mm Hg or lower were not associated with poorer cognitive outcomes in older adults compared with targets of 150 mm Hg, as has been a concern.

That study further showed greater cognitive benefits with the lower SBP target among blacks than whites.

The current study adds confirmatory evidence supporting the argument of greater benefits than risks with the lower blood pressure target, Kevin N. Sheth, MD, an associate professor of neurology and neurosurgery at the Yale School of Medicine, New Haven, Connecticut, told Medscape Medical News.

"While the findings are not surprising, they are reassuring from a clinical perspective," said Dr Sheth, who co-moderated the session.

"Consistent with previous data, the study indicates that a clinical stroke event rate, even from a theoretical hypoperfusion perspective, doesn't appear manifest, and that's reassuring in terms of implementing those stricter blood pressure guidelines."

Dr Tsao reports ownership of stock in Illumina, Biogen, and Amgen. Dr Sheth has disclosed no relevant financial relationships.

ANA 2017: 142nd Annual Meeting of the American Neurological Association. Abstract M150. Presented October 16, 2017.

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