Low diastolic blood pressure (DBP) may harm the myocardium, leading to coronary heart disease (CHD) events, according to results of an observational cohort study.1

This study was published in the Journal of the American College of Cardiology as a mechanistic explanation to a late-breaking session on optimal blood pressure in patients with coronary artery disease, presented at the 2016 European Society of Cardiology Congress in Rome.2

The effect was especially pronounced in patients with DBP <60 mm Hg and systolic blood pressure (SBP) >120 mm Hg.


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“There is now strong evidence from SPRINT (Systolic Blood Pressure Intervention Trial) that more intensive systolic BP goals, as low as 120 mm Hg when measured in the right setting, are beneficial for some patients.3 However, this will mean more medications,” John William McEvoy, MB, MHS, study lead author and assistant professor of cardiology at Johns Hopkins University School of Medicine, told Cardiology Advisor in an email.

“What our paper hopefully does is it puts some of the focus back on diastolic BP, or at least it should remind us not to ignore diastolic BP. Many physicians will be aware of this, but our paper drives home the point that diastolic BP is important for coronary perfusion, and that lowering of diastolic BP comes with a price in terms of myocardial ischemia and CHD events,” Dr McEvoy added.

In the Atherosclerosis Risk In Communities (ARIC) cohort study, researchers sampled adults in 4 communities in the Midatlantic, Southeast, and Midwest regions who enrolled in the study from 1990 to 1992. Patients who had CVD or heart failure were ineligible, leaving a study population of 11,565.

Patients with a DBP <60 mm Hg were more than twice as likely to have elevated high-sensitivity cardiac troponin-T (hs-cTnT; ≥14 ng/L) compared with those who had a baseline DBP of 80 mm Hg to 89 mm Hg (see table). Researchers also observed a linear inverse relationship between a DBP <65 mm Hg and elevated hs-cTnT when modeling DBP using linear splines.

Elevated hs-cTnT  (≥14 ng/L) by DBP

Diastolic blood pressure
(mm Hg)

Odds Ratio
(95% confidence interval)

<60

2.24 (1.22–4.10)

60–69

1.52 (1.00–2.32)

70-79

1.02 (0.71–1.47)

80-89

1 (reference)

90-99

1.06 (0.61–1.83)

≥100

1.54 (0.63–3.78)

Low DBP at baseline also was independently associated with progressive myocardial damage as assessed by estimated annual change in hs-cTnT over 6 years. Compared with those who had a DBP of 80 mm Hg to 89 mm Hg at baseline, estimated annual change in hs-cTnT was beta 1.5 ng/L (95% CI: 0.5-2.4 ng/L) per year higher in the DBP <60 mm Hg group and beta 1.0 ng/L (95% CI: 0.3-1.6 ng/L) per year higher in the DBP 60 mm Hg to 69 mm Hg group.

At a median follow-up of 21 years, patients with a DBP <60

mm Hg also had a higher risk for CHD (HR: 1.5; 95% CI:  1.2-1.9) and all-cause mortality (HR: 1.3; 95% CI: 1.1-1.6) compared with a DBP 80 mm Hg to 89 mm Hg. There was also an increased risk for CHD among those with a DBP of 60 mm Hg to 69 mm Hg (HR: 1.23; 95% CI: 1.05-1.44) and 70 mm Hg to 79 mm Hg (HR: 1.20; 95% CI: 1.05-1.37). However, patients in those 2 groups did not have an increased risk for all-cause mortality.

“Besides avoiding overly aggressive titration of BP meds to reduce SBP in persons who are starting off with an already low DBP, I would not recommend any ‘treatment’ to increase DBP,” Dr McEvoy said. “This would probably be harmful for most patients and would not be supported by our data. Really, the take-home is that, when lowering systolic BP, which is supported by SPRINT and a number of other analyses, physicians should be keeping an eye on diastolic BP to ensure this is not dropping below 60 mm Hg.”

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References

  1. McEvoy JW, Chen Y, Rawlings A, et al. Diastolic blood pressure, subclinical myocardial damage, and cardiac events. Implications for blood pressure control. J Am Coll Cardiol. 2016. doi:10.1016/j.jacc.2016.07.754.
  2. Steg PG. FP 5732. Optimal blood pressure in CAD patients: is there a J-curve phenomenon? Insights from 22,695 hypertensive CAD patients in the CLARIFY registry. Presented at European Society of Cardiology Congress. August 27-31, 2016; Rome, Italy.
  3. Group SR, Wright JT Jr., Williamson JD, et al; for the SPRINT Research Group. A randomized trial of intensive vs standard blood-pressure control. N Engl J Med. 2015;373: 2103-2116. doi:10.1056/NEJMoa1511939.