The tightest control of the major risk factors for heart disease seems to provide the greatest protection against cardiovascular trouble, a new study shows.
And so the current guidelines for risk factors, such as blood pressure and low-density lipoprotein (LDL) cholesterol, might need to be tightened even further, said Stephen J. Nicholls, MD, an assistant professor of molecular medicine at the Cleveland Clinic, and author of the report, which appeared in the Journal of the American College of Cardiology.
"It is clear that each benefit we have in terms of lowering LDL cholesterol and blood pressure is going to be important. The lower you get those measurements, the better," Dr. Nicholls said.
Dr. Nicholls and his colleagues looked at data on the arteries of 3.437 men enrolled in seven different trials at the Cleveland Clinic. Ultrasound of the arteries provided information on the volume of the fatty deposits in the linings of the blood vessels-deposits that can grow until they block blood flow, causing a heart attack or stroke.
The least amount of growth was seen in those men who had the lowest levels of LDL cholesterol, the "bad" kind of cholesterol that contributes to the fatty deposits, and the lowest levels of blood pressure.
"The rationale for the current analysis was the belief that you should get lower LDL cholesterol and lower blood pressure, and that the benefit is greatest in getting both low," Dr. Nicholls said. "In fact, patients who had the best results in terms of growth of the deposits were those with the lowest LDL and lowest blood pressure."
Cholesterol And Blood Pressure Guidelines
Specifically, the least growth was seen in men with LDL blood cholesterol readings under 70 milligrams per deciliter and systolic blood pressure the top number) under 120, he said.
The guideline for blood pressure says that men at risk can have systolic readings as high as 140 (having consistent systolic readings from 120 to 139 is called "prehypertension"). With blood cholesterol, the current recommendation is for an LDL level of 100 for men at high risk of heart disease, with "consideration being given to lowering it to 70.
"If you are at high risk, LDL should be below 70," he said. "For blood pressure, you get the greatest benefit if it is below 120."
An accompanying editorial co-authored by Jonathan Tobis, MD, of the University of California, Los Angeles, said the results did not necessarily indicate that tighter control of cholesterol and blood pressure would be beneficial.
"You need clinical endpoints to know," said Dr. Tobis, director of interventional cardiology research at the UCLA's David Geffen School of Medicine. "They have positive effects on total plaque volume, but the question is whether that corresponds to clinical events such as myocardial infarction (heart attack] and stroke. I suspect that they do, but we haven't proven that yet, and these trials don't prove it."
The composition of a fatty deposit might be as important as its size, Dr. Tobis said. Some plaques might be less stable than others, thus prone to rupture and block a blood vessel, he said. "One of the studies included in the report showed that aggressive lowering of LDL reduced the size of the deposits, but we don't know clinically if that makes a difference or not," Dr. Tobis said. "Lowering LDL enough might stabilize a plaque so that you get an adequate result."
More Clinical Studies Needed
Dr. Nicholls said he agreed with that assessment. While the study indicates that lowering existing guideline levels for LDL cholesterol and high blood pressure could reduce risk considerably, he noted that "we need a lot more clinical studies showing that putting the guidelines below those levels would be beneficial."