Diastolic Blood Pressure Lowering and Implications for Blood Pressure Control
What is the independent association of diastolic blood pressure (DBP) with myocardial damage (using high-sensitivity cardiac troponin-T [hs-cTnT]) with coronary heart disease (CHD), stroke, or death over 21 years?
The investigators studied 11,565 adults from the ARIC (Atherosclerosis Risk In Communities) study, analyzing DBP and hs-cTnT associations as well as prospective associations between DBP and events. To model the prospective association between baseline DBP categories and clinical outcomes, the authors constructed Cox models, adjusted for the variables in the model. They further verified the proportionality of the hazards visually and with Schoenfeld residuals.
Mean baseline age was 57 years, 57% of patients were female, and 25% were black. Compared with persons with baseline DBP between 80 and 89 mm Hg, the adjusted odds ratio of having hs-cTnT ≥14 ng/L at baseline was 2.2 and 1.5 in those with DBP <60 mm Hg and 60-69 mm Hg, respectively. Low DBP at baseline was independently associated with progressive myocardial damage on the basis of estimated annual change in hs-cTnT over the 6 years between visits 2 and 4. Compared with a DBP of 80-89 mm Hg, a DBP <60 mm Hg was associated with incident CHD and mortality, but not with stroke. The DBP and incident CHD association was strongest with baseline hs-cTnT ≥14 ng/L (p value for interaction < 0.001). Associations of low DBP with prevalent hs-cTnT and incident CHD were most pronounced among patients with baseline SBP ≥120 mm Hg.
The authors concluded that particularly among adults with an SBP ≥120 mm Hg, and elevated pulse pressure, low DBP was associated with subclinical myocardial damage and CHD events.
This study reports that low DBP was cross-sectionally associated with prevalent myocardial damage and prospectively associated with incident CHD events and mortality, but not with incident stroke. Furthermore, the association between low DBP and incident CHD appeared to be strongest among those with evidence of preceding myocardial damage at baseline. Taken together, these data form a compelling argument that excessively low DBP may directly harm the myocardium. It appears that lower may not always be better with respect to BP control and clinicians need to carefully consider risks and benefits before pushing BP control below current guideline targets, particularly if the DBP falls below 60 mm Hg. Based on this and other evidence, careful and thoughtful consideration is needed before changing/lowering current BP targets.
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