Chronic Smoking Tied to Clots

New evidence confirms that chronic smokers, including those who look and feel healthy, undergo activity in their bloodstreams that can lead to excessive clotting and possibly to heart attacks, researchers said Monday.

Habitual smoking causes excessive interaction of the blood components that trigger clotting, said scientists in a study published Monday in Circulation, an American Heart Assn. journal.

The formation of blood clots in arteries serving the heart muscle can result in a heart attack.

Scientists at Vanderbilt University’s School of Medicine in Nashville compared six apparently healthy male habitual smokers, ages 24 to 46, with six healthy nonsmoking volunteers for their study. The habitual smokers smoked one or more packs a day and during the study smoked one pack a day.

Dr. John Oates, chairman of medicine at Vanderbilt, said that he and his colleagues interpret increased activity of the “blood platelet” found in smokers as a reflection of injuries to blood vessel walls caused by as yet unidentified components of cigarette smoke.

When the smooth interior lining of a blood vessel is injured, the blood’s microscopic, disc-shaped platelets immediately begin to stick to the damaged area. During platelet “activation,” several substances are secreted as part of the clot-forming process, including the chemical thromboxane A2, researchers said.

During the study, levels of thromboxane A2 were measured after it had been metabolized and excreted by the body.

The “significantly elevated” levels of a metabolic product of the chemical in the urine of smokers studied is evidence of platelet dysfunction, researchers said.