Patients who have suffered a heart attack should avoid driving in heavy traffic for at least two to three weeks after leaving hospital, say US researchers.
Driving in heavy traffic exposes patients to high levels of pollution, which was found to damage the heart either by inflaming the heart muscle or by reducing blood flow to the organ.
Traffic was also found to increase stress levels, which can be detrimental to the heart.
For this latest study, the researchers examined ECGs from 48 patients, living in an area of Boston, who had been hospitalised for a heart attack, unstable angina or worsening symptoms of coronary artery disease.
They focused on identifying the presence of a conductivity change called ST-segment depression, a marker for inadequate blood flow to the heart or inflamed heart muscle.
They then examined the relationship between these ST-segment changes using data on levels of traffic pollutants.
Overall, the researchers found that patients living in areas with high levels of traffic pollution showed greater signs of ST-segment depression.
Patients recovering in the first two to three weeks after leaving hospital had the highest risk of changes in ST-segment depression, compared with patients who had been recovering for months after being discharged.
Lead researcher Dr Diane Gold, from Harvard University in Boston, said: 'Our study provides additional rationale to avoid or reduce heavy traffic exposure after discharge since traffic exposure involves pollution exposure as well as stress.'
- Circulation Online 2008