Single cigarette has damaging effect on heart
Smoking just one cigarette is enough to impair the function of the heart so that it has to work harder -- a phenomenon doctors at East Carolina University Brody School of Medicine witnessed for the first time using an ultrasound technology called echocard
The damaging effect of the cigarette was immediately apparent on the left ventricle, which did not fully relax to clear the chamber of blood. When this happens on a regular basis, it can cause an increase in the pressure within the ventricle and, over enough time, lead to heart trouble, even failure.
Doctors have long known that smoking contributes to heart disease; one in five of the nation's 950,000 cardiovascular deaths each year is attributed to smoking. They also have known that the heart appears to repair quickly once a smoker quits, so that the risk of coronary heart disease decreases by 50 percent one year after stopping, according to the American Heart Association.
The ECU study is significant because it shows an immediate, damaging consequence of a single cigarette.
"We watched this as it occurred," said Dr. Vincent Sorrell, an ECU cardiologist and lead investigator on the study. He presented the results this weekend during the initial phase of peer review at a meeting of the American Society of Echocardiography.
"The effects weren't drastic -- there weren't any diastolic heart failures -- but it was apparent something was going on," he said.
Dr. Adam Goldstein, who leads anti-smoking efforts at the University of North Carolina at Chapel Hill, said the research adds to the scientific literature about how even one cigarette is harmful.
"I think that we've long known, at least for the last 10 to 15 years, that there isn't a safe threshold," Goldstein said. "Even with one or two a day, we know that people have a higher risk of heart disease and death, and this helps us understand how that is the case."
Goldstein said the information will be especially helpful for prevention efforts aimed at teenagers, who are most likely to begin smoking. Showing them a videotape of the immediate heart impairment might be more effective than warning them about cancer and other health problems that develop after years of smoking.
Sorrell said he began the study after some of his patients who smoked complained of shortness of breath. Ordinary tests showed nothing wrong with their hearts or their lungs.
"I wondered if something else was going on," he said. So he decided to mount a study using echocardiography, which bounces sound waves off the heart to produce images of the chambers and valves.
He and his team enlisted 27 healthy young adults, most of whom were not smokers. They randomly divided the participants into two groups: One group's participants smoked a cigarette; the other's chewed nicotine gum.
Both groups were hooked up to the echocardiograph. Measure-ments were taken before the subjects began smoking or chewing, and then immediately after.
Later, Sorrell examined the echocardiograph results and measured various heart functions without knowing whether the subjects had smoked a cigarette or chewed the gum. One measurement, in particular, showed an abnormal function occurring in the left ventricle during the heart's relaxation beat.
The data revealed that the abnormality was only apparent in the smokers, not in the nicotine gum chewers, suggesting that something other than nicotine was the culprit. But, Sorrell said, he wouldn't rule out nicotine yet, because additional research is needed.
"This really raises more questions than it answers," he said.
Scientists elsewhere have explored nicotine's adverse affects on the heart, but have yet to pinpoint a direct cause-and-effect relationship. Still, studies have shown that nicotine raises heart rates and elevates the systolic blood pressure, which is the pressure in the heart's chamber when it contracts.
Sorrell said he suspects that the heart changes he observed may be caused by carbon monoxide, which is inhaled from the burning tobacco smoke and has a direct impact on cardiac function, particularly on ventricular diastolic pressure.
He said he will launch more specific studies to determine which of the 4,000 chemicals and byproducts present in tobacco smoke creates the problem.
"We are only beginning to unravel the mystery," he said.