The researchers found that particles, particularly those associated with traffic fumes, can affect the heart’s ability to conduct electrical signals in people with serious coronary artery disease.

Writing in Circulation: Journal of the American Heart Association, the scientists described their study of patients with coronary artery disease in the Boston area.

They visited patients over several weeks following their discharge from hospital to measure a change in the electrical conductivity of their hearts known as an ST-segment depression.

The average levels for all pollutants included in the analysis were below accepted or proposed National Air Quality Standard thresholds, but the researchers found an increase in the amount could cause problems with the heart’s electrical function.

“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 Gold, the study’s senior author and an associate professor of medicine and environmental health at Harvard University in Boston.

“Effects were greatest within the first month after hospitalisation, and for patients who were hospitalized for a heart attack or had diabetes.”

The researchers said their evidence suggests that people who have recently had heart attacks – and even healthy people – should avoid being around heavy traffic after being discharged from hospital.

The American Heart Association and the American College of Cardiology recommend that some heart patients should avoid driving for two to three weeks after leaving the hospital in order to avoid stress.

“Our study provides additional rationale to avoid or reduce heavy traffic exposure after discharge, even for those without a heart attack, since traffic exposure involves pollution exposure as well as stress,” Ms Gold said.

Increased levels of PM2.5, black carbon and sulfur dioxide were associated with ST-segment depression, according the study, but no significant link was found with increased levels of carbon monoxide.

Kate Martin

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