Controversy Now Moves to New Diastolic BP Threshold

January 29, 2020

Isolated diastolic hypertension is now more prevalent, owing to the definition of hypertension used in the most recent US blood pressure guidelines, but the condition does not appear to be associated with increased risk for cardiovascular outcomes, a new study suggests.

"We believe the lower diastolic threshold in the new US guidelines has cast the net too widely," lead author John William McEvoy, MBBCh, told Medscape Medical News.

McEvoy, who is professor of preventive cardiology at the National University of Ireland, Galway, added: "Our data suggest there is no harm of having a diastolic pressure above 80 mmHg if the systolic is below 130 mmHg and that the new 80 mmHg diastolic threshold means that 12 million adults in the US will be labeled as hypertensive but will not benefit from the diagnosis and may be given unnecessary treatment."

The study was published online January 28 in JAMA.

In defining hypertension, the 2017 American College of Cardiology (ACC)/American Heart Association (AHA) blood pressure guideline lowered the cutoff from ≥140/90 mmHg to ≥130/80 mmHg.

The recommendation to lower the diastolic threshold for hypertension from 90 mmHg to 80 mmHg was based on expert opinion, not on trial data. This change has major implications with respect to isolated diastolic hypertension, now defined as a systolic blood pressure <130 mmHg with a diastolic pressure ≥80 mmHg, the authors write.

With the current study, the researchers aimed to estimate the prevalence of isolated diastolic hypertension using both the new and the old definitions in the US adult population and to assess the associations of both definitions with incident cardiovascular disease, heart failure, and chronic kidney disease.

The investigators used the National Health and Nutrition Examination Survey (NHANES), which includes 9590 adults and is designed to be nationally representative of the civilian adult population in the United States. Using the new 2017 ACC/AHA guideline definition, they estimated the prevalence of isolated diastolic hypertension to be 6.5%. Using the old definition, they estimated it to be 1.3%.

Among those newly classified as having isolated diastolic hypertension, an estimated 0.6% also met the guideline threshold for antihypertensive therapy, McEvoy and colleagues report.

They then investigated prognostic implications of having isolated diastolic hypertension with the two definitions in three separate longitudinal cohorts. The primary analysis was conducted using the Atherosclerosis Risk in Communities (ARIC) study cohort, which includes 8703 adults with 25-year follow-up and which gives information on the risk for incident atherosclerotic cardiovascular disease, heart failure, and chronic kidney disease.

These findings were then validated in two external cohorts by examining the association of isolated diastolic hypertension with all-cause and cardiovascular mortality.

Results showed that compared with normotensive ARIC participants, isolated diastolic hypertension, as defined the 2017 ACC/AHA guidelines, was not significantly associated with incident atherosclerotic cardiovascular disease (hazard ratio [HR], 1.06); heart failure (HR, 0.91), or chronic kidney disease (HR, 0.98).

Results were also null for cardiovascular mortality in the two external cohorts (HR, 1.17 and 1.02; both nonsignificant).

There were no significant associations with isolated diastolic hypertension, as defined by the older criteria, and any adverse outcome.

McEvoy said these findings have many important implications.

"If an individual has normal systolic blood pressure (<130 mmHg according to new guidelines), our data suggest that it doesn't really matter what the diastolic blood pressure is," he commented.

"In most individuals, the systolic and diastolic pressures track very closely, so if the systolic is 130, the diastolic is likely to be around 80; however, in some people, the systolic and diastolic pressures do not correlate quite as well," he said.

"Some individuals have increased diastolic pressure, and this is much more common now with the new guideline threshold of 80 mmHg. We estimate that 12 million more US adults will now be classed as having isolated diastolic hypertension, and as the guidelines do not distinguish between different types of hypertension, they could be labeled and treated inappropriately."

McEvoy noted that there has always been a question about whether isolated diastolic hypertension is associated with adverse outcomes. "There have been mixed results with the old definition, which used 90 as the threshold for diastolic pressure, but the new cut point of 80 means more people are being diagnosed with hypertension without any evidence to support a benefit of this."

McEvoy said he is a strong proponent of the new 130 mmHg threshold for systolic pressure. "But the lowering of the diastolic threshold from 90 to 80 was just based on expert opinion. There is no solid evidence behind this recommendation. Our data suggest there is no harm of having a diastolic over 80, and I do not believe it is appropriate to use diastolic pressure for defining hypertension and treatment targets."

He believes the current results are enough to prompt discussion about whether the new 80 mmHg threshold for diastolic pressure is appropriate. "I think it is enough to start a conversation," he concluded. "There needs to be other studies from other cohorts to verify our findings."

Guideline Chair Responds

Commenting on the study for Medscape Medical News, Paul Whelton, MD, chair of the 2017 ACC/AHA blood pressure guideline committee, said he agreed that systolic pressure is the more important measure for predicting cardiovascular risk and for making drug treatment decisions.

"This is increasingly true in progressively older adults, to the point that in the 2017 ACC/AHA guideline, systolic blood pressure alone was recommended as the target (<130 mmHg) for adults 65+ years. The central importance of systolic blood pressure was highlighted several times in the guideline," said Whelton, who is professor of global public health at Tulane University School of Medicine, New Orleans, Louisiana.

"However, the writing committee wanted to provide guidance to clinicians regarding the best response to levels of diastolic blood pressure in adults," he said

"The randomized, controlled trial evidence for benefit of antihypertensive drug treatment in adults with a diastolic pressure over 90 mmHg is strong, based on older trials, but no trial has documented a benefit of drug therapy in adults with a diastolic BP 80–90 mmHg. The ACC/AHA recommended treatment in this group when there was evidence of prior cardiovascular disease or a 10-year risk of atherosclerotic cardiovascular disease estimated to be 10+%, based on expert opinion," Whelton noted.

"No event-based treatment trials have been conducted in adults with isolated diastolic hypertension, and there is no treatment recommendation for such persons in the 2017 ACC/AHA blood pressure guideline," he added. "As such, I conclude that the new JAMA report, while interesting, has no direct bearing on the 2017 ACC/AHA guideline recommendations."

McEvoy disagrees with Whelton this point. "These guidelines very clearly drop the diastolic blood pressure threshold for hypertension from 90 mmHg to 80 mmHg, and as such have major implications for the diagnosis and possible treatment of isolated diastolic hypertension," he responded.

JAMA. Published online January 28, 2020. Abstract

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