Baltimore—More isn’t necessarily better when it comes to lowering diastolic blood pressure.

A study published in the Journal of the American College of Cardiology reports new evidence of an association between driving diastolic blood pressure too low with medications and damage to heart tissue.

Those findings were the result of analysis by Johns Hopkins Medicine-led researchers of medical records gathered over three decades on more than 11,000 Americans participating in a federally funded study.

Study authors caution, however, that their research doesn’t prove direct cause, only a statistically significant increase in heart-damage risk among those with the lowest levels of diastolic blood pressure.

“The take-home message is there is increased likelihood that if we use blood pressure drugs to push patients’ systolic blood pressures down to 120, which is a strategy supported by recent clinical trials, the consequence in those starting out with low diastolic blood pressures (e.g., below 80) may be that the diastolic number falls so low that we risk doing damage,” explained J. William McEvoy, MBBCh, MHS, assistant professor of medicine at Johns Hopkins. “Our key finding suggests that for some patients, there should perhaps be modification of intensive anti-hypertensive treatment recommendations issued last year as a result of the SPRINT trial, and that physicians shouldn't look at driving down the top blood pressure number (the systolic number) in isolation without considering implications of lowering the bottom number.”

The SPRINT trial, which was released last fall, demonstrated protective cardiovascular benefits when physicians aggressively treated high blood pressure down to 120/80 mm of mercury, with a primary emphasis on keeping systolic at no higher than 120.

“Although the SPRINT trial gave good, solid results that lower systolic pressure may benefit some high-risk patients, we wanted to check for potential unintended adverse outcomes that might come with such aggressive blood pressure treatment in patients with low diastolic blood pressure,” McEvoy said in a Johns Hopkins Medicine press release.

For the analysis, the researchers used patient data from the Atherosclerosis Risk in Communities (ARIC) Study, a National Institutes of Health epidemiological project started in 1987. Participants at the start of the project had an average age of 57 and were 57% female and about 25% African-American. Participants were followed for 21 years in a series of five visits, with the last check-in for testing occurring in 2013.

Using blood samples, ARIC investigators performed high-sensitivity cardiac troponin testing. Results indicate that, after controlling for age, race, sex, diabetes, drinking, smoking and other factors, 1,087 participants with diastolic blood pressure below 60 mm of mercury were statistically twice as likely to have troponin-indicated heart damage, compared to participants with higher diastolic blood pressures ranging from 80 to 89 mm of mercury.

In addition, about 3,728 patients with a diastolic blood pressure between 60 and 69 mm of mercury were 52% more likely to have heart damage as measured by the high-sensitivity troponin test, with some 120 people in this range showing elevated troponin levels, according to the report.

Those with a diastolic blood pressure range from 70 to 99 mm of mercury showed no greater risk of troponin-associated heart damage, study authors note.

On average, participants with the lowest diastolic blood pressure below 60 mm of mercury were 49%more likely to have heart disease and 32% more likely to die of any cause.

“Particularly among adults with an SBP ≥120 mm Hg, and thus elevated pulse pressure, low DBP was associated with subclinical myocardial damage and CHD events,” study authors conclude. “When titrating treatment to SBP <140 mm Hg, it may be prudent to ensure that DBP levels do not fall below 70 mm Hg, and particularly not below 60 mm Hg.”

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