By Michael H. Crawford, MD, Editor
SYNOPSIS: An analysis of three large prospective databases showed the 2017 American College of Cardiology/American Heart Association revised definition of isolated diastolic hypertension as > 80 mmHg rather than the previous definition of > 90 mmHg resulted in a 5% higher prevalence of diastolic hypertension. This was not significantly associated with cardiovascular disease outcomes.
SOURCE: McEvoy JW, Daya N, Rahman F, et al. Association of isolated diastolic hypertension as defined by the 2017 ACC/AHA blood pressure guideline with incident cardiovascular outcomes. JAMA 2020;323:329-338.
In 2017, the American College of Cardiology/American Heart Association (ACC/AHA) hypertension guidelines redefined diastolic hypertension (DH) as > 80 mmHg based on expert opinion, not trials. McEvoy et al sought to establish the prevalence of DH under these revised guidelines and to assess the association between DH so defined with cardiovascular disease (CVD) outcomes.
To accomplish these goals, they analyzed cross-sectional data from the National Health and Nutrition Examination Survey (NHANES) database from the 2013-2016 survey of U.S. adults and longitudinal data from the Atherosclerosis Risk in Communities (ARIC) study second examination in 1990-1992 with follow-up through 2017. The longitudinal results were validated in NHANES from 1988-1994, NHANES 1999-2014, and the Give Us a Clue to Cancer and Heart Disease (CLUE) II cohort from the 1989 baseline data. In NHANES and ARIC, blood pressure (BP) was measured after five minutes of sitting, and the mean of two to three measurements were used. In ARIC, high-sensitivity troponin and NT-proBNP also were measured. The prespecified cardiovascular disease (CVD) outcomes in ARIC were atherosclerotic (AS) CVD, heart failure (HF), and chronic kidney disease (CKD). ASCVD was a composite of myocardial infarction, ischemic stroke, or CVD death. Sensitivity analyses were performed for age, systolic BP, and antihypertensive treatment.
After excluding patients with missing data and age < 20 years, 9,590 NHANES patients were available, of which DH was present in 1.3% by JNC 7 criteria (> 90 mmHg) and 6.5% by 2017 ACC/AHA criteria. Few were recommended for drug therapy by either definition (1.6% and 2.2%, respectively). Among the > 14,000 ARIC patients aged 46-69 years, after excluding those with systolic hypertension, 2% met JNC 7 criteria for DH and 11% met ACC/AHA criteria. Those with isolated DH were more likely younger, male, Black, overweight, or had lipid abnormalities. During a median follow-up of 25 years, compared to normal BP, there were no statistically significant associations between DH and the composite outcome of ASCVD, HF, or CKD (hazard ratio [HR], 1.03; 95% confidence interval [CI], 0.93-1.15) or any of the individual endpoints. Sensitivity analyses did not change the results. In the NHANES validation cohort, DH was not associated with all-cause or CVD death (HRs, 0.92 and 1.17, respectively). Similar results were seen in the CLUE validation cohort (HR, 1.02 for both endpoints). Also, in ARIC, there were no significant associations between DH and cardiac biomarkers (troponin, BNP). The authors concluded that in this analysis of several populations of U.S. adults, isolated DH by the 2017 ACC/AHA definition was more prevalent than with the JNC 7 definition, but was not significantly associated with CVD outcomes.
The 2017 ACC/AHA guidelines for the treatment of hypertension caused quite a bit of controversy over the stricter definition of systolic hypertension to > 130 mmHg. Such measurements mainly revolved around older individuals in whom systolic BP naturally tends to increase with age and in patients with conditions such as coronary artery disease in whom higher pressures may be required to perfuse the myocardium. At the other end of the spectrum are subjects with isolated DH who more frequently tend to be young men. The new definition of DH raised the prevalence of it several-fold compared to the previous JNC 7 definition. This decision was based largely on older epidemiologic data that showed an increase in the risk of developing CVD at diastolic BPs > 75 mmHg and expert opinion. This carried psychological, social, and financial implications, so it is not a trivial matter.
However, this analysis of NHANES and ARIC data did not demonstrate an increase in CVD events or mortality. Perhaps more importantly there was no signal of subclinical organ damage, as evidenced by no significant changes in troponin and BNP. Prior studies have shown an association with DH and the development of later systolic hypertension, which was not analyzed in this study. Despite this possibility, there is no indication for drug treatment of isolated DH. This advice is consistent with the Hypertension Optimal Treatment (HOT) study, which did not show any benefit to reducing diastolic BP from 90 to 80 mmHg. Periodic surveillance for systolic hypertension would seem reasonable.
There were some limitations to the work of McEvoy et al. Although several sensitivity analyses and comparisons to other databases were conducted, there always is the possibility of residual confounding. Also, in ARIC, the lowest age for participation was cut off at 48 years, so these results may not apply to younger individuals. Still, the results were consistent with the NHANES data, where the lowest age was 20 years, and CLUE, where the median age was 42 years.
In addition, the studies used included patients on antihypertensive therapy. In such patients, any intervention would be escalation of therapy to further lower diastolic BP. Sensitivity analyses to adjust for this factor did not change the results. Finally, in ARIC, participants had to self-identify as either Black or white, so the results may not apply to other racial or ethnic groups. On the other hand, NHANES included all ethnicities in proportion to the U.S. population, and the results were the same in this population.
Despite all these potential weaknesses, this was a large study of three population cohorts that all demonstrated the same findings. Isolated DH does not seem to be a pathological entity, yet may represent about one-quarter of U.S. adults who have been recommended for BP therapy since the introduction of the 2017 ACC/AHA guidelines. It is time to re-examine the diastolic component of the controversy over these new guidelines.