Smoking and having low levels of "good" cholesterol can be extra risky in people who''ve already had a heart attack, said researchers from Wake Forest University Baptist Medical Center (WFUBMC) today at the American Heart Association''s annual fall conference.
"We found that blood vessel disease progresses an average of three to four times faster in heart attack survivors than in people without heart disease," said lead researcher John R. Crouse, M.D., professor of internal medicine and public health sciences. "Smoking or low levels of ''good'' cholesterol speeds up progression even further, increasing vulnerability to repeat heart attacks and strokes."
To determine how various risk factors affect the body''s blood vessels, WFUBMC researchers used ultrasound technology to measure vessel wall thickness in 280 adults over a three-year period. Thickened vessel walls are an early sign of atherosclerosis, the buildup of fatty deposits that causes heart attacks and strokes.
Measurements were taken of the carotid artery, the major vessel supplying blood to the brain. This vessel was studied because it can be measured non-invasively, unlike the heart''s arteries. Research has shown that vessel disease normally occurs throughout the body, so the status of the carotid arteries is a good indicator of the status of the heart''s arteries.
The researchers compared how several well-known risk factors - age, gender, smoking, blood glucose, body mass index, race, menopausal status, high blood pressure and cholesterol - affect the rate of wall thickening.
Using sophisticated computer analyses, they were able to evaluate how each risk factor affected a group of heart attack victims (with at least one heart vessel more than 50 percent blocked) and compare the effects to a group without diseased heart vessels.
"Carotid wall thickening progressed three to four times faster in those who had had heart attacks than in those without heart vessel disease," said Greg Terry, M.S., research associate in endocrinology, who presented the results. "This effect was not completely explained by standard risk factors. It suggests that something else - perhaps genetics or risk factors we''re not yet aware of - makes them more susceptible to vessel disease in the first place."
In those who had had heart attacks, two risk factors - levels of "good" or high-density lipoprotein (HDL) cholesterol and smoking history - had the greatest effects on artery thickening.
HDL is known as "good" cholesterol because high levels seem to protect against heart attack. The researchers found that when HDL levels were below 35 mg/dl, wall thickening progressed five times faster than when levels were 54 mg/dl or above. (The American Heart Association says people with levels below 35 have the greatest risk of heart disease.) Effective ways to increase good cholesterol are exercise, weight loss and smoking cessation.
Smoking a pack of cigarettes a day for eight years corresponded to wall thickening rates that were four times faster than among non-smokers.
"If you''ve been diagnosed with heart vessel disease, these results suggest that you should pay particular attention to HDL levels and should stop smoking, if you haven''t already," said Crouse.
Crouse said the study results suggest that ultrasound measurements might be used as a screening tool to identify individuals at increased risk for heart attacks or strokes.
"Measuring how rapidly arteries thicken could possibly predict who is likely to develop atherosclerosis and the heart attacks and strokes it causes," said Crouse.
Participants in the study were adults who had been hospitalized and undergone heart catheterization to detect blockages in the heart''s arteries. The study included equal numbers of men and women and equal numbers of people with and without heart vessel disease.
Other members of the research team were Mark Espeland, Ph.D., biostatistician, Timothy Morgan, Ph.D., biostatistician, and Rong Tang, M.D., sonographer.
The research was funded by a grant from the National Heart, Lung and Blood Institute.
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