Sept. 8, 2008 -- After a heart attack, it might be best to
steer clear of traffic for a while. New research shows that traffic pollution
can be dangerous for people with heart
In people with serious coronary artery disease, tiny particles of air
pollution and black carbon from traffic exhaust fumes may cause ST-segment depression, an EKG finding that usually signals an
inadequate supply of oxygen and nutrients to the heart muscle, according to a
report in Circulation: Journal of the American Heart Association.
For the study, 48 heart patients in the Boston area wore special monitors
that checked for ST-segment depression intermittently over the course of a
year. When the particles and black carbon in the air increased, so did the
instances of ST-segment depression. Effects were greatest within the first
month after hospitalization and for patients who had been hospitalized for a
heart attack or had diabetes.
Authors note that previous studies have shown exposure to road traffic can
trigger heart attacks and that air pollution increases the risk for cardiac
The American Heart Association and the American College of Cardiology
already recommend that some heart patients, particularly those who have had
heart attacks, avoid driving for several weeks, especially in heavy traffic,
because of the 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," Diane R.
Gold, MD, the study's senior author and an associate professor of medicine and
environmental health at Harvard University, says in a news release.
The study participants were between 43 and 75 years old. Researchers visited
them several times at three-month intervals, hooking them up to a monitor for
24-hour stretches. The participants had all been hospitalized for a heart
attack, unstable angina, or worsening symptoms of stable coronary artery
disease, and had all undergone angioplasty or stent implantation. Most were
male, and 25% had diabetes.
It is not known how the carbon and air particles cause ST-segment
"Further research is needed to evaluate whether the pollution-related
ST-segment depression that we see is related to increased heart muscle
inflammation, reduced oxygen flow, oxidative stress, or increased risk of
arrhythmias," Gold says.