Did the 2017 ACC/AHA blood pressure guideline get it wrong in reducing the diastolic threshold to define hypertension from 90 to 80 mmHg?

Among the panoply of cardiovascular disease (CVD) risk factors, hypertension reigns supreme. ¹ Hypertension definitions and treatment thresholds have varied substantially over the years, reflecting an ever‐evolving evidence base. ² Initial hypertension guidelines focused on controlling diastolic blood pressure (BP) to < 90mmHg ³ but over time, a stronger relationship between systolic blood pressure and CVD outcomes became apparent and subsequent guidelines provided systolic BP targets also. ⁴ In recent years, important differences in guideline recommendations for the diagnosis and treatment of hypertension have emerged, which have contributed to some uncertainty among clinicians and their patients.

The 2017 American College of Cardiology/American Heart Association (ACC/AHA) guidelines ⁵ define hypertension as a BP cutoff of greater than or equal to 130/80mmHg, which contrasts with the 2018 European Society of Cardiology (ESC) ⁶ and the 2019 National Institute of Clinical Excellence (NICE) ⁷ guideline cutoff of greater than or equal to 140/90mmHg. The lower systolic BP threshold in the ACC/AHA guideline is supported by a number of lines of evidence, not least the 2015 Systolic BP Intervention Trial (SPRINT). ⁸ Whether the lower diastolic threshold of 80mmHg is associated with a prognostic significance has come under question, particularly when the systolic BP is below 130 mmHg, and, as such, focus on the entity of isolated diastolic hypertension (IDH) is growing.

In this issue of The Journal of Clinical Hypertension, Cesena and colleagues report the results of their retrospective analysis of a large single‐center cohort from a Brazilian executive health screening program. ⁹ A total of 33,594 individuals were included. Measurement of BP was performed manually in both arms by a medical doctor after 5 or more minutes of seated rest, with the average BP recorded. Comparing the prevalence of hypertension defined by the ACC/AHA and ESC/NICE guidelines showed a 2.6‐fold relative increase in arterial hypertension with the former definition, largely attributable to an 8.7‐fold increase in IDH (84% of all new hypertension diagnoses) in this cohort. Overall, the absolute increase in hypertension was 33.6%. This increase in the prevalence of hypertension and IDH exceeds that seen in previous population‐based epidemiologic studies, ¹⁰ highlighting the impact that these lower ACC/AHA BP thresholds may have on the prevalence of hypertension in a more clinical population.

Another key finding from this interesting study is the detailed analysis of the metabolic profiles of patients with newly diagnosed hypertension by the 2017 ACC/AHA definition. When compared to patients with isolated systolic hypertension (ISH) or combined systolic‐diastolic hypertension (SDH), patients with IDH were younger and had lower rates of metabolic syndrome and diabetes, lower BMIs, more favorable triglyceride profiles, and an overall lower CVD risk estimate. Compared to normotensive individuals, those with IDH were found to be at higher risk for CVD by the Framingham 10‐year risk score; however, the absolute risk remained low at 3.6%. These results may, in part, provide an observational explanation as to why IDH when categorized by the ACC/AHA definition appears to not be associated with adverse CVD outcomes, as has been recently reported. ¹⁰

An important conclusion the authors draw is that 2017 ACC/AHA 2017 guideline overemphasizes the role of diastolic BP in the diagnosis of hypertension. This is supported by their findings, which show that large numbers of patients with an overall low CVD risk are newly diagnosed with hypertension based on elevated diastolic BP alone. Some limitations need to be considered. The study population was derived from a health screening program largely comprising of individuals of higher socioeconomic class and of European ancestry making widespread applicability to the general population difficult. Also, BP recordings were recorded on a one‐off basis in a clinical setting which does not allow for correcting of a potential white coat effect.

Though not assessed in the current study, an area of ongoing investigation is the prognostic significance, if any, of IDH. Previous studies have provided conflicting results. ¹¹ IDH by the more conservative ESC/NICE definition has been shown to be associated with CVD outcomes in several studies, ¹² , ¹³ whereas no association was found in others. ¹⁴ , ¹⁵ , ¹⁶ To date, three large analyses of CVD outcomes among those with IDH by the more lenient 2017 ACC/AHA definition have been carried out. Once systolic BP is < 130mmHg, Korean data have shown that diastolic BPs of 80‐89mmHg do not contribute significantly to CVD outcomes. ¹⁷ A recent JAMA publication ¹⁰ studying IDH in the Atherosclerosis Risk in Communities (ARIC) population also did not show any significant association, particularly for the ACC/AHA definition.

These findings contrast with a large electronic health record study, which suggested a modest increase in CVD risk when IDH was defined by the ACC/AHA definition. ¹⁸ The reasons for these discordant results remain to be determined but one obvious difference between studies that suggest no excess CVD risk for IDH by the ACC/AHA definition ⁹ , ¹⁰ and the report suggesting increased risk ¹⁸ was that rigorous measurements of BP were performed in the former studies whereas the latter study examined BP values entered into an electronic health record as part of routine clinical care from a variety of clinical settings. This is important to note because the measurement of diastolic BP is not easy and improper technique could cause bias. ¹⁹

In summary, the present study clearly highlights the potential for a substantial increase in the prevalence of hypertension when applying the 2017 AHA/ACC BP cutoffs, and that this is largely due to an increased prevalence of IDH. Patients with IDH in this Brazilian study were more metabolically benign than those with ISH or SDH and had lower calculated ASCVD risk scores. Ongoing work will be needed to clarify the prognostic implications of IDH by the 2017 ACC/AHA definition to allow informed decisions regarding treatment.

DISCLOSURES

No disclosures are reported.

McGrath BP, McEvoy JW. Did the 2017 ACC/AHA blood pressure guideline get it wrong in reducing the diastolic threshold to define hypertension from 90 to 80 mmHg? J Clin Hypertens. 2020;22:1200–1201. 10.1111/jch.13899