Commentary

2017 ACC/AHA hypertension guidelines: Toward tighter control

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Release date: October 1, 2018
Expiration date: September 30, 2019
Estimated time of completion: 1 hour

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In 2017, the American College of Cardiology (ACC), American Heart Association (AHA), and 9 other professional associations published a new guideline on high blood pressure in adults.1 Their document addresses a range of topics relevant to preventing, diagnosing, and managing hypertension. It incorporates evidence from randomized controlled trials, including the Systolic Blood Pressure Intervention Trial (SPRINT),2 systematic reviews, and expert opinion.

The new guidelines contain many noteworthy changes, some of which are generating intense debate and discussion. Here, we provide our opinions to help practicing clinicians broaden their perspective and make informed decisions about management.

ACC AND AHA ARE NOW RESPONSIBLE FOR HYPERTENSION GUIDELINES

The Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC), organized by the National Heart, Lung, and Blood Institute, began issuing hypertension guidelines in 1977. Based on observational and clinical trial data, succeeding JNC reports recommended ever-lower blood pressure goals, with emphasis shifting to treatment of systolic hypertension.

The last official JNC report—JNC 7—was published in 2003.3 In 2013, the Institute transferred the responsibility for cardiovascular prevention guidelines to the ACC and AHA.4

A report from the panel members appointed to JNC 8 was published independently in 2014.5 It focused on a few key questions and used evidence limited to randomized controlled trials. In this report, the panel relaxed the goals for many subgroups, leading to criticism from many professional societies and from some members of the panel writing group.6

WHAT'S NEW IN THE 2017 GUIDELINES?

The new ACC/AHA guidelines contain a number of changes from previous documents that have been the topic of debate.

New definition and classification of hypertension

Strong recommendation, based on moderate-quality evidence­.

Classification of hypertension
The new ACC/AHA guidelines redefine hypertension. The category of “prehypertension” has been eliminated, and stage 1 hypertension is now defined at a lower blood pressure threshold of 130/80 mm Hg or higher. The earlier threshold of 140/90 mm Hg for diagnosis of hypertension is now considered stage 2 hypertension. Table 1 compares the new classification with the earlier JNC 7 classification.
Figure 1. With the 2017 guideline definition, the prevalence of hypertension is higher.

Figure 1. With the 2017 guideline definition, the prevalence of hypertension is higher.

Muntner et al7 calculated that this new classification would increase the prevalence of hypertension to about 46% of US adults (up from about 32% under the previous definition), with 31 million Americans who were previously deemed healthy now labeled as having hypertension (Figure 1). Among those under age 45, the prevalence is more than doubled.

Our opinion. While this new classification is intended to promote closer monitoring and earlier intervention to lower cardiovascular event rates, creating a new level of disease may lead to more pharmacologic treatment for those with lower risk, without emphasis on lifestyle modifications.

Emphasis on measurement technique and out-of-office measurements

Strong recommendation, based on expert opinion, for accurate measurement of blood pressure in the office, high-quality evidence from systematic review for out-of-office measurement.

Appropriate management of hypertension entails accurate blood pressure measurement. While office-based measurement remains the most commonly used method, this “snapshot” may not reflect a patient’s true baseline blood pressure.

Out-of-office measurements. Based on the results of a systematic review commissioned by the guideline committee, out-of-office measurements are now recommended to confirm the diagnosis of hypertension and to assess response to therapy.

Ambulatory blood pressure monitoring should be strongly considered as the preferred method for out-of-office monitoring; home blood pressure monitoring can be done if ambulatory monitoring is not feasible. Ambulatory monitoring provides additional information on nighttime blood pressure, including the dipping status (normal defined as a nighttime blood pressure decrease of 10% to 20%). Ambulatory monitoring predicts long-term cardiovascular outcomes independent of office blood pressure, and elevated nighttime pressure and non-dipping have been shown to be independently associated with increased cardiovascular mortality rates.8,9 Unfortunately, despite evidence supporting its use, ambulatory blood pressure monitoring is not widely available for a variety of reasons, including high cost (roughly $2,000–$4,000) and minimal reimbursement.

Out-of-office measurements can also detect white coat hypertension and masked hypertension. White coat hypertension is defined as blood pressure that is elevated in the office but normal in an out-of-office setting, and masked hypertension is blood pressure that is normal in the office and elevated in an out-of-office setting. Currently, pharmacologic therapy is not recommended to treat white coat hypertension, and treatment for masked hypertension should be the same as for sustained hypertension.

While the guidelines do not comment specifically on manual office measurement vs automated office measurements using devices that take multiple measurements with the patient alone in the room to reduce the white coat effect, they acknowledge “increasing evidence” favoring the use of automated office measurement.

Proper technique for measuring blood pressure is appropriately emphasized; correct patient positioning, allowing a period of rest, and using the appropriate cuff size are all important. Unfortunately, many busy clinical practices may not follow correct technique when measuring blood pressure in the office, leading to misdiagnosis and unnecessary pharmacologic therapy that may result in adverse events.

Of note, the SPRINT trial, which informed many of the new guideline recommendations, followed a strict protocol of blood pressure measurement with an automated device, checking sitting blood pressure 3 times at 1-minute intervals, with the patient alone in the room and without an observer present at many of the sites.10

Most guidelines11,12 agree on an average of at least 135/85 mm Hg as the threshold for diagnosing hypertension by home monitoring, or an average daytime pressure of at least 135/85 mm Hg by ambulatory monitoring, corresponding with office-based blood pressure of 140/90 mm Hg.­ However, the new guidelines recommend a lower threshold of 130/80 mm Hg for both home monitoring and average daytime ambulatory monitoring, corresponding with an office blood pressure of 130/80 mm Hg. They do not specify whether the office-based measurement is manual or automated.

Our opinion. Since office-based measurement will likely remain the principal method for managing hypertension due to constraints with ambulatory or home monitoring, the use of automated devices for office measurement should be strongly considered. Studies have shown that, compared with routine office measurements, automated measurements more closely approximate those obtained by ambulatory and home blood pressure monitoring.13

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