September 11, 2008
Riding behind that nasty, exhaust-belching 18-wheeler in heavy traffic
can affect more than just your lungs.
Research reported in Circulation: Journal of the American Heart Association finds that microscopic particles in polluted air can have an adverse affect on the heart's ability to conduct electrical signals in people with serious coronary artery disease.
In a recent study of 48 Boston-area patients, all of whom had coronary artery disease, 24-hour Holter monitors were used to examine electrocardiograms for the conductivity change called an ST-segment depression, which may indicate inadequate blood flow to the heart or inflamed heart muscle.
The average 24-hour levels for all pollutants included in the analysis were below accepted or proposed National Air Quality Standard thresholds, meaning patients were breathing air considered healthy.
"We found that an elevation in fine particles, from non-traffic as well as traffic sources, and black carbon, a marker for traffic, predicted ST-segment depression," said Diane R. Gold, M.D., M.P.H., the study's senior author and an associate professor of medicine and environmental health at Harvard University in Boston, Mass. "Effects were greatest within the first month after hospitalization, and for patients who were hospitalized for a heart attack or had diabetes."
Previous studies have documented that exposure to road traffic can trigger heart attacks, and that particulate air pollution increases the risk for cardiac death or heart attack.
"When coal sales were banned in Dublin, Ireland, and black smoke concentrations declined by 70 percent within the next 72 months, cardiovascular deaths fell by 10 percent," said Gold, citing a study published in 2002.
The ST-segment changes Gold observed were not associated with symptoms in these patients, all of whom had experienced in-hospital procedures to examine or open up their coronary arteries.
Nevertheless, the findings expand the evidence that air pollution can affect heart health, either through inflaming the heart muscle or through reducing blood flow to the heart. It suggests the need for greater vigilance by physicians and heart patients in the weeks after discharge from the hospital, researchers said.
