Cholesterol levels predict extent of artery narrowing

Cholesterol levels in the blood appear to be an accurate barometer of the amount of fatty plaque clogging a person's coronary arteries, according to a multicenter European study.

The investigators say that blood cholesterol levels are a "strong and independent" link to coronary artery disease (CAD) and heart attack risk. Their report appeared in the American Heart Association journal Arteriosclerois, Thrombosis, and Vascular Biology.

Researchers used angiograms, a type of X-ray, to peer inside the coronary arteries of 2,587 men and women at 18 European medical centers. All the patients had "angina" chest pain resulting from narrowed coronary arteries. Those who had the highest blood cholesterol had the most severe narrowings, reports the study's co author, Dr. Simon Thompson of the Medical Statistics Unit at London's School of Hygiene and Tropical Medicine.

This is the first time that researchers have comprehensively linked the actual level of cholesterol and other lipids to the amount of coronary artery disease in such a large study, researchers say. "The implications of this study are that cholesterol, HDL and LDL are major culprits in CAD, and that dietary recommendations concerning cholesterol should be stringently maintained," says Thompson. Cholesterol is piggy-backed through the bloodstream in particles of HDL (high-density lipoprotein) and LDL (low- density lipoprotein). Population studies have shown that risk of heart attack increases when total cholesterol and LDL levels are elevated and levels of "good" HDL are low.

In their study the European investigators used a scoring system of 0 to 4 to classify patients, with the lowest score indicating no narrowing and the highest score indicating blockages of at least 50 percent in all four coronary arteries studied. Blood concentrations of the major lipids -- including total cholesterol, HDL cholesterol and LDL cholesterol -- were measured.

The researchers also measured triglycerides and a fat particle called lipoprotein(a) that may adversely affect blood clotting.

Patients were placed in one of three groups, based on their lipid levels. Those in the highest third had a 3.84- fold higher incidence of CAD than those with serum levels in the remaining two thirds. Individuals in the highest third for triglycerides and Lp(a) had about 1.5 times greater risk than those in the lowest third.

The findings provide clear evidence that all of cholesterol -- including LDL and HDL -- is "strongly related to the presence and extent of coronary artery disease" and this underlies their importance as predictors of heart disease risk, the scientists say. "Arteriosclerotic diseases are multifactorial in origin, and risk of heart attack has been found to be related to cholesterol, LDL and HDL, but it has not before been so clearly shown how serum lipid profiles are related to the extent of coronary artery disease," says Thompson.

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