DALLAS, Sept. 12 -- Cigarette smoking contributes to heart disease by choking off the heart's blood supply, according to a study in today's Circulation: Journal of the American Heart Association.
Cigarette smoking is a major risk factor for coronary heart disease. The by-products of smoking damage the linings of arteries and promote the build-up of blood vessel-clogging plaque.
This is the first study to demonstrate that the harmful effects of smoking extend beyond the heart's large arteries into the network of tiny blood vessels that supply blood to most of the heart muscle. These small vessels are not visible during angiography, a standard X-ray procedure that detects blood flow abnormalities.
Researchers in London and Zurich used positron emission tomography (PET) to measure blood flow through coronary arteries in 11 smokers and 8 non-smokers. They found that the additional blood supply that should be available to the heart during stress was reduced by 21 percent in smokers compared with the non-smokers.
"Smokers had less blood supply to their hearts, which is an indicator of future heart attacks or strokes," says the study's lead author Philipp A. Kaufmann, M.D., an assistant professor at University Hospital in Zurich Switzerland. Individuals in the study did not have symptoms of heart disease.
"Our study shows that PET can be used to investigate damage at a stage before heart disease is present and is possibly still reversible," says Paolo Camici, M.D., senior author of the study.
The mechanisms by which smoking damages the coronary system is not fully understood but the researchers say their findings support the hypothesis that free radicals, or unstable oxygen molecules, in cigarette smoke may be responsible.
"We provide evidence that the free radicals present in cigarette smoking are responsible for the initial damage to the circulatory system," says Camici, a professor at Imperial College in London. "The proof is that when individuals were given an antioxidant like vitamin C, the blood flow was restored." In the study, researchers administered vitamin C intravenously to normalize blood flow in smokers. Smoking cigarettes is known to deplete levels of vitamin C and other antioxidants.
"Vitamin C had an immediate effect on blood flow, but long-term use of vitamin C has not been studied yet," says Kaufmann.
The authors suggest that it might be worth testing whether daily oral vitamin C supplementation would have protective effects on the development of heart disease in smokers in a long-term, large-scale trial. They note that the greater amount of vitamin C in the Mediterranean diet could be one reason why there is not more heart disease in the Mediterranean region despite a higher prevalence of smoking there.
Co-authors are Tomaso Gnecchi-Ruscone, M.D.; Marco di Terlizzi, M.D.; Klaus P. Schafers, MSc; and Thomas F. Luscher, M.D.
NR00-1171 (Circ/Kaufmann)
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