Since results of the SPRINT (Systolic Blood Pressure Intervention Trial) study were revealed last fall, physicians and others in the healthcare industry have debated the merits of lowering the systolic blood pressure target. In that trial, adults who were at least 50 years old, had an increased risk of cardiovascular events and did not have diabetes benefited from reducing their systolic blood pressure to less than 120 mm Hg.
Still, there has been no consensus on whether all patients would benefit from a lower target. A recent study, presented at the European Society of Cardiology Congress in Rome, showed that a lower blood pressure goal might not always be better.
The observational study, which involved data from 45 countries, found that low systolic and low diastolic blood pressures were associated with an increased risk of cardiovascular events in patients with hypertension and coronary artery disease.
Lead researcher Philippe Gabriel Steg, MD, a professor of cardiology at Université Paris–Didero in France and Imperial College in the U.K., and colleagues published their results online in the Lancet on Aug. 30.
The researchers analyzed data from 22,672 patients with stable coronary artery disease who received treatment for hypertension and enrolled in the CLARIFY registry from Nov. 26, 2009, to June 30, 2010. They defined hypertension as a blood pressure of 140/90 mm Hg.
At baseline, the mean age was 65.2 years old, while 75 percent of patients were men and 67 percent were white. The mean systolic and diastolic blood pressures were 133.7 mm Hg and 78.2 mm Hg, respectively.
After a median follow-up period of five years, a systolic blood pressure of 140 mm Hg or more and a diastolic blood pressure 80 mm Hg or more were each associated with an increased risk of cardiovascular events.
In addition, a systolic blood pressure of less than 120 mm Hg was associated with a 56 percent increased risk for the primary outcome, which was the composite of cardiovascular death, MI or stroke. Meanwhile, a diastolic blood pressure of less than 70 mm Hg was associated with a 41 percent increased risk for the primary outcome.
The researchers said there a systolic blood pressure of less than 120 mm Hg and a diastolic blood pressure of less than 70 mm Hg were associated with a steep J-curve, which they defined as an increase in the risk of cardiovascular events below a certain blood pressure level. There was a steep J-curve for the primary outcomes as well as for the individual components of cardiovascular death, all-cause death, MI and hospital admission for heart failure.
The researchers mentioned that the results only applied to patients with hypertension and coronary artery disease and should not be extrapolated for patients with hypertension and other conditions.
“Compared with post-hoc analyses of blood pressure-lowering trials, there are some disadvantages to using data from an observational registry, such as the open nature of the information (including events), the possible lower accuracy of outcome identification, and the greater heterogeneity of the treatment used,” the researchers wrote. “In addition, the casual blood pressure values from our study are less accurate and standardized than in randomized trials or than blood pressure values obtained from ambulatory measurements; conversely, they are also more readily applicable to community practice. Also, these results derive from an observational study and are prone to confounding. Only dedicated randomized controlled trials comparing blood pressure targets can provide definitive evidence of the risk associated with each blood pressure threshold.”
Future studies should evaluate whether patients with a systolic blood pressure of more than 140 mm Hg and a high pulse pressure should have a target of less than 140 mm Hg, according to the researchers. They also said that the studies should examine whether the presence of coronary artery disease, a history of stroke or diabetes or old age plays a role in determining the ideal blood pressure target.