Lower Blood Pressure Goal in Diabetics Does Not Translate to Improved Outcomes
ATLANTA—The goal systolic blood pressure (SBP) of less than 130 mm Hg for patients with diabetes should be reconsidered after the release of new evidence showing that intensive BP control offers no clinical advantage when compared with standard control in diabetic patients, according to presenters at the 59th Annual Scientific Sessions of the American College of Cardiology.
The Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC-7) and American Diabetes Association recommend a goal BP of less than 130/80 mm Hg in persons with diabetes, although evidence to support this recommendation is lacking, particularly in diabetic patients with coronary artery disease.
In examining data retrospectively from a diabetic subset of patients enrolled in the International Verapamil SR-Trandolapril Study (INVEST), in which investigators compared BP treatment strategies, diabetics with coronary artery disease who achieved an SBP lower than 115 mm Hg had an increased risk for mortality compared with those who achieved an SBP 130 to 140 mm Hg, according to lead investigator Rhonda M. Cooper-DeHoff, PharmD, MS.
Of 22,576 patients with hypertension and coronary artery disease who were enrolled in INVEST, she and her team focused their analysis on the 6,400 patients with diabetes. For this new analysis, patients were categorized according to their on-treatment BP level. Those with an SBP of 140 mm Hg or greater, which constituted 34% of the patients, were categorized as “not controlled”. Those who achieved an SBP of less than 130 mm Hg were classified as “tight control”, and those with an SBP from 130 to 140 mm Hg were classified as “usual control”.
As expected, patients in the not controlled group had a nearly 50% greater risk of the combined end point of death, myocardial infarction (MI), or stroke when compared with the usual care group (event rates: 19.8% vs. 12.6%). The occurrence of this outcome was not significantly different between the tight control and usual control groups (12.7% vs. 12.6%).
Among the 5,077 United States patients in the study, the risk of dying from any cause was increased significantly by 15% in the tight control group compared with the usual care group, said Dr. Cooper-DeHoff, Associate Professor of Pharmacy and Medicine at the University of Florida in Gainesville. This increase in mortality started at about three years; the difference in the risk of dying between the two groups persisted with extended follow-up, which reached 11 years in some patients.
When further classifying BP increments of 5 mm Hg, she found that the excess risk of dying started when SBP dropped below 115 mm Hg, was increased even further when SBP was lowered to 110 mm Hg or less.
“Less than 140 [mm Hg] is the message we need to be getting out there; less than 130 probably isn't necessary to achieve benefit and may be harmful in some populations,” Dr. Cooper-DeHoff said. “We wonder whether it is time to rethink lower blood pressure goals in patients with diabetes and coronary artery disease.”
A second study that reinforced this finding was the ACCORD (Action to Control Cardiovascular Risk in Diabetes) Blood Pressure trial, in which 4,733 high-risk diabetic patients were enrolled. Patients were assigned to intensive BP control (target SBP less than 120 mm Hg) or standard control (target SBP less than 140 mm Hg).
At one year, average SBP levels were 119 mm Hg in the intensive-control group and 134 mm Hg in the standard-control group.
At a mean follow-up of 4.7 years, the annual rate of cardiovascular mortality, MI, or stroke was 1.9% in the intensive-control group vs. 2.1% in the standard-control group, a nonsignificant difference. The end point of death was also not significantly different between the two groups, said lead investigator William C. Cushman, MD, Chief of the Preventive Medicine Section at the Veterans Affairs Medical Center in Memphis.
Consistent with other BP treatment trials, the risk of stroke was reduced by 41% with intensive treatment, he said, but adverse events were more likely with intensive BP control. The rates of serious adverse events were 3.3% and 1.3% with intensive control vs. standard control, respectively.
An elevation in serum creatinine levels and the incidence of syncope, bradycardia, hyperkalemia, and hypotension were all more common with intensive control. Despite the small decrement in renal function with tight control, there were no differences between the tight and standard control groups in development of end-stage renal disease or progression to dialysis.
“Most of us have been teaching for many years that the lower the blood pressure, the better the outcomes; therefore, seek to get the blood pressure lower,” said Elijah Saunders, MD, who heads the hypertension section in the Division of Cardiology at the University of Maryland in Baltimore. “The data we have suggest that we still cannot recommend bringing blood pressure down to less than 120 mm Hg as a way of reducing risk. ”