Men who have had coronary bypass surgery may significantly lower the rate at which fatty substances accumulate in their coronary arteries by taking cholesterol-lowering drugs and following a low-fat diet, USC researchers reported Thursday.
The study said that coronary arteries accumulate fewer new fat deposits, and that existing fat deposits accumulated less slowly after the study's participants began taking the drugs and following the diet.
Furthermore, the study showed for the first time, in a small number of the study's participants, that lowering blood cholesterol can reverse the process of atherosclerosis, or hardening of the arteries.
The study by Dr. David H. Blankenhorn and his USC colleagues appears in the new issue of the Journal of the American Medical Assn.
In an accompanying editorial, Dr. Eugene R. Passamani of the National Heart, Lung and Blood Institute urged caution in interpreting the data because, he said, the study's technical design contained flaws that might have skewed some of the results.
The federally funded study involved 162 men in Los Angeles aged 40 to 59. One group received the drugs colestipol and niacin, in addition to the low-fat diet; the other group received only a less stringent low-fat diet. All of them were nonsmokers and none had abnormal blood pressure, although their heart disease had been severe enough to have required bypass surgery.
In both groups, X-rays of the coronary arteries were taken at the start of the study and at subsequent intervals of two years or four years.
The USC team concluded that after two years of treatment there was significantly less overall deterioration in both the new blood vessels that had been implanted during the bypass operation and in the patients' other coronary arteries. In the treated group, total cholesterol levels fell 26% and other blood fats called triglycerides were down 22%. Cholesterol is a waxy substance in the blood that, depending upon the fatty proteins attached to it, can contribute to heart and blood vessel disease.
More importantly, Blankenhorn attributed the relatively healthy state of the arteries in the treated group to a 43% reduction in low-density lipoprotein, a major component of the fibrous plaques that clog blood vessels, and to a 37% increase in the "good" type of cholesterol, known as high-density lipoprotein.
"We can't say whether it was the drugs or the low-fat diet that did the trick. It was both," Blankenhorn said in an interview. "The message is that lowering LDL (low-density lipoprotein) and increasing HDL (high-density lipoprotein) makes a difference."
Passamani said that the study "makes a most persuasive argument" for the experimental combination therapy.
More than 220,000 patients each year have coronary bypass surgery. Passamani said that many doctors and patients may have believed that the surgery alone would confer long-term benefits, but that does not always occur because fat continues to be deposited in arteries after surgery.
Body of Evidence
Previous studies have provided evidence that reducing cholesterol--with drugs or diet, or both--has a beneficial effect on heart patients. The USC study shows the largest cholesterol decrease over a two-year period yet reported, according to Blankenhorn. It also provides the largest amount of X-ray evidence to demonstrate the effects of treatment on coronary arteries.
The drugs used in the study, colestipol and niacin, have been available for many years and have been used in previous studies. But they can cause side effects such as itching, rash, nausea, heartburn and constipation.
Colestipol is a resin that binds with bile acid from the digestive system and removes it from the body, reducing the levels of cholesterol by forcing the body to use the fats to make more bile acid. Niacin is a B-complex vitamin found in lean meats, fish, poultry, nuts and cereals.
Blankenhorn warned against taking high doses of niacin, available without prescription, unless done under the care of a doctor.
New Drug on Horizon
Despite the USC study, the future use of these drugs is unlikely to increase significantly because of the expected licensing later this year of a new type of cholesterol-lowering drug, called lovastatin, which has been shown in tests to be exceptionally effective and have fewer side effects.
The diet followed by the treated group advised patients to cut in half the amount of red meat as well as fish and poultry--because even fish and poultry contain some cholesterol; replace high-fat dairy products with low-fat or non-fat products; eat more fruits and vegetables and more grains, pasta, cereal and rice, and eat everything else in moderation.