Startling new blood pressure findings
Published: Tuesday, 16-Nov-2004
A new study led by The Cleveland Clinic shows that giving blood pressure lowering medication to heart disease patients with a “normal” blood pressure dramatically reduces risk of adverse cardiac events and slows disease progression.
In the CAMELOT trial, researchers enrolled patients with coronary heart disease and an average blood pressure of 129/78, which is considered completely “normal” by current standards. Patients were given one of two types of blood pressure lowering drugs or a placebo (a sugar pill).
After two years of treatment with the anti-hypertensive drug amlodipine, a drug in a class known as calcium channel blockers, patients experienced a 31-percent reduction in major adverse cardiovascular events, including heart attack, stroke, death, hospitalization for chest pain and need for angioplasty or bypass surgery.
These unexpected results raise a provocative question: How low a blood pressure is low enough for patients with coronary heart disease?
“The reduction in risk for the amlodpine group was surprisingly large,” said CAMELOT principal investigator Steven Nissen, M.D., a Cleveland Clinic cardiologist. “The patients in this trial were treated with the best existing therapies – 84 percent received cholesterol-lowering drugs and 95 percent received aspirin. Their blood pressures were already well below current treatment guidelines. Yet adding amlodipine to state-of-the-art medications further reduced cardiovascular events in this patient population.
“The CAMELOT study demonstrates the critical importance of lowering blood pressure in patients with heart disease and suggests that current guidelines do not go far enough in recommendations for blood pressure targets in patients with coronary disease,” Dr. Nissen said.
The CAMELOT trial enrolled 1,991 patients at 100 study centers in the United States, Canada and Europe. Patients were divided into three groups: One-third received amlodipine, a calcium channel blocker, (brand name Norvasc); one-third received enalapril, an angiotensin-converting enzyme (ACE) inhibitor, (brand name Vasotec); and one-third received a placebo.
In both the amlodipine and enalapril groups, blood pressure was reduced about 5/3 mm Hg to approximately 124/76. The 31-percent reduction in major adverse cardiovascular events in the amlodipine group was highly statistically significant. Although the group receiving enalapril experienced a 15-percent reduction in adverse events, the difference was not statistically significant.
Of the 1991 patients in the study, 274 underwent intravascular ultrasound (IVUS) examination at the start of the study and at the end of 24 months. IVUS uses a miniaturized ultrasound probe to measure the amount of plaque inside coronary arteries. In the group that received a placebo, more plaque had built up in the coronary arteries at the end of 24 months. In the group that received amlodipine, no disease progression occurred. The differences were particularly dramatic in patients with starting blood pressures above the mean of 129/78.
“This is the first study to demonstrate that blood pressure reduction can slow or halt the buildup of plaque in the coronary arteries,” Dr. Nissen said. “Previously, only cholesterol lowering drugs have been shown to slow disease progression. The current study demonstrates that blood pressure lowering drugs produce similar benefits.”
One of the surprises in the study, Dr. Nissen said, was the greater effect of the calcium channel blocker, amlodipine, compared with the ACE inhibitor, enalapril. Dr. Nissen suspects that the longer duration of action of amlodipine likely explains the difference. “Because enalapril is shorter-acting, it may not have reduced blood pressure for the full 24 hours with once-per-day administration,” he said.
Complete CAMELOT results will be published Nov. 10 in the Journal of the American Medical Association.