One More Puff Could be Enough to Cause a Heart Attack

FOR RELEASE: 2 p.m. CT, FridayMarch 2, 2001

CONTACT:Karen Hunter or Carole BullockAHA News Media RelationsSan Antonio Marriott RivercenterPh. (210) 554-6255

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American Heart Association meeting report: One more puff could be enough to cause a heart attack

SAN ANTONIO, March 2 -- Cigarette smoking seems to have an acute effect that may increase the risk of a heart attack following each cigarette smoked, according to a study presented today at the American Heart Association's 41st Annual Conference on Cardiovascular Disease Epidemiology and Prevention.

"The most important thing a person can do to avoid a heart attack is to quit smoking. There probably would be an immediate benefit," says the study's lead author Murray A. Mittleman, M.D., director of cardiovascular epidemiology at Beth Israel Deaconess Medical Center in Boston.

In a study of heart attack patients, researchers found that those who smoked a cigarette within six hours before having a heart attack had bigger blood clots in their arteries than smokers who reported a longer period of time between their last cigarette and the onset of heart attack symptoms.

The blood clot, or thrombus, that leads to a heart attack was larger in smokers compared to non-smokers, despite the fact that some smokers had fewer overall risk factors for heart disease. Smokers' clots averaged 16.9 millimeters squared (mm2) compared to 13.7 mm2 in non-smokers.

"We know that the long-term effects of smoking raise the risk of cardiovascular disease. This study shows a short-term association with the formation of bigger clots that may increase the risk or severity of a heart attack," says Mittleman. "Smoking a cigarette can enlarge the blood clot and tip the balance."

Heart attacks are usually caused by blood clots that form in plaque-filled arteries that supply blood to the heart. Fatty plaque build-up in the arteries tends to evolve over time. Factors such as physical activity can increase the heart rate or blood pressure, which makes the plaque more likely to rupture.

If only a small clot forms on the ruptured clot, there is still some blood flow and a person may not have a heart attack at all or suffer a minor heart attack. However, if smoking a cigarette causes a larger clot to form, it may completely block blood flow to the heart and a heart attack can occur. The less blood that gets to the heart, the more severe the heart damage, says Mittleman.

Researchers studied 902 heart attack patients who were part of a larger study to determine the factors leading to heart attack onset. All had symptoms of heart attack and were given angiograms before the blocked artery was opened with balloon angioplasty or stenting.

After their procedures individuals were asked if they smoked and if so, when they smoked their last cigarette prior to experiencing heart attack symptoms.

There appears to be a correlation between blood clot size and the amount of time between the last cigarette smoked and the onset of heart attack symptoms, says Mittleman. The average clot size of those who smoked a cigarette within six hours before a heart attack was 23 mm2. Those who had smoked a cigarette between 6 and 24 hours of symptom onset had an average clot size of 12.5 mm2. For those who reported at least 24 hours between smoking a cigarette and experiencing heart attack symptoms, average clot size was even smaller at 6.7 mm2.

Thirty-nine percent of the patients undergoing emergency coronary angioplasty procedures were smokers. Smokers tended to be male, younger, more physically fit and more likely to have single vessel disease. The smokers' average age was 54 while the non-smokers were around 65 years old. Among smokers, 75 percent were male compared to 65 percent of the non-smokers. Thirty-six percent of the smokers were considered physically active compared to 29 percent of the non-smokers. Smokers also recognized the symptoms of heart attack more readily and arrived at the hospital an average of 16 minutes faster than non-smokers.

Other researchers in this study include Satyendra Giri, M.D.; Joseph Mitchel, D.O.; Francis J Kiernan, M.D.; Jeffrey A. Hirst, M.D.; Jonathan Clive, Ph.D.; Daniel B. Fram, M.D.; Daniel I. Simon, M.D.; and Jeffrey J. Popma, M.D.

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NR01 - 1254 (Epi/Mittleman)

Media Advisory: Dr. Mittleman can be reached at (617) 632-7653. His e-mail is [email protected]. His fax is (617) 632-7675. (Please do not publish contact information.)