Monday, November 27, 2017

The 2017 ACC/AHA Clinical Practice Guideline for High Blood Pressure

- Jennifer Middleton, MD, MPH

The 2017 Clinical Practice Guideline for High Blood Pressure was released 2 weeks ago by the American College of Cardiology (ACC), the American Heart Association (AHA), and 9 other professional societies. The AAFP was not one of these societies and has not yet endorsed the guideline. The nearly 200 page document is quite comprehensive, including a new classification scheme and updated treatment recommendations for patients with a range of co-morbidities. Given the size and scope of this Clinical Practice Guideline (CPG), it's unsurprising that some of its recommendations are being met with enthusiasm and others, perhaps, less so.

The 2017 CPG redefines normal versus abnormal blood pressure using both systolic and diastolic measurements. They define normal BP as a systolic of <120 mmHg and a diastolic of <80 mmHg, elevated BP as a systolic of 120-129 mmHg and a diastolic of <80 mmHg, stage 1 hypertension as a systolic of 130-139 mmHg or a diastolic of 80-89 mmHg, and stage 2 hypertension as a systolic of > 139 mmHg or a diastolic of > 89 mmHg. To make these diagnoses, the authors stress the importance of both accurate in-office BP measurements and ambulatory BP monitoring.

These definitions will significantly increase the number of persons in the United States with a diagnosis of elevated BP and hypertension. The authors justify this increase by citing meta-analyses showing progressively increasing hazard ratios for cardiovascular disease (CVD) risk beginning at a systolic of 120 mmHg or greater and/or a diastolic of 80 mmHg or greater; given the relatively small numbers of individuals who experience CVD complications at lower BPs, however, the absolute CVD risk increase in this population is modest.

The authors appropriately stress the use of nonpharmacological interventions including weight loss, increased physical activity, a healthy diet, and limited alcohol use, and they cite literature showing the efficacy of each of these interventions. These nonpharmacological interventions are the mainstay of treatment for elevated BP as well as stage 1 hypertension in individuals not at increased risk of CVD. They advise initiating pharmacologic treatment for stage 1 hypertension for individuals with diabetes, chronic kidney disease, established CVD, and/or whose 10-year ASCVD risk is calculated to be equal or greater to 10%; this group also includes persons over the age of 65. All individuals with stage 2 hypertension (>140/90 mmHg) should employ nonpharmacological and pharmacologic interventions, which is unchanged from previous guidelines.

The choice of a systolic of 130 mmHg to define hypertension is not without controversy. A commentary on the new guidelines points out that:
The use of a risk-based approach as well as more aggressive BP targets reflect a strong influence in these guidelines from the SPRINT trial....while SPRINT treated patients to an SBP goal of less than 120 mmHg, because repeated BP measurements in SPRINT are likely lower than what is seen in clinical practice, the guideline recommends a target of less than 130 mmHg, not 120 mmHg.
Similarly, "[t]he selection of a 10% ASCVD risk threshold appears also to have been a compromise, being higher than the threshold used to classify high risk in the lipid guidelines (7.5%) and different from that used in SPRINT (15% Framingham risk)." SPRINT's influence is significant, given its shortcomings, and these compromises feel more expert opinion-based than evidence-based. It should be noted that SPRINT's principal investigator is also one of the co-chairs of this CPG, though, according to the manuscript, he excused himself from acting as chair during the group's discussions about SPRINT. Another commentary notes the lack of data "regarding the balance of harms and benefits of treatment" in patients with this new definition of stage 1 hypertension. Several meta-analyses, including one developed for this guideline, have shown reduced CVD events in patients treated to a systolic BP target of 130 but not reduced mortality.

It's difficult to argue with this CPG's emphasis on nonpharmacologic treatment, ambulatory BP monitoring, team-based care, integration of QI efforts, and population health advocacy. Its new BP diagnosis definitions and treatment goals, however, may be more open to discussion, especially as no primary care societies were involved in their development. As Dr. Lin discussed last week on the blog, you can count on AFP to provide ongoing commentary on this and other new guidelines as they emerge.