Heart-disease patients should limit their time outdoors if they live in a highly polluted city, new research suggests, as microscopic air pollution particles may lead to decreased heart function.
Researchers in Boston, Mass., found that pollution particles impair the heart's signalling pathways, which may lead to inadequate blood flow to the heart and inflammation of the heart muscle.
The findings are published in Circulation: Journal of the American Heart Association.
Researchers studied 48 people who had been hospitalized for heart-disease symptoms or heart attack and monitored their hearts' electrical impulses with a 24-hour monitoring device.
They then compared the results to air pollution measures taken at a Harvard School of Public Health monitoring site.
The pollution measures were taken an average of 18 kilometres from the patients' homes.
The findings showed that an increase in fine particles of air pollution was associated with the decreased ability of the heart to send electrical signals.
The research adds to previous studies that have linked exposure to air pollution to an increased risk for heart attack and stroke.
"When coal sales were banned in Dublin, Ireland, and black smoke concentrations declined by 70 per cent within the next 72 months, cardiovascular deaths fell by 10 percent," senior study author Dr. Diane R. Gold said in a statement, citing a 2002 study.
As well, a study published in May in the Archives of Internal Medicine found that long-term exposure to air pollution led to an increased risk of developing a blood clot in the leg known as deep vein thrombosis.
In this study, the changes in heart function did not cause symptoms in the patients.
However, the findings suggest that patients and their doctors should be more aware of the risk factors that will exacerbate heart disease.
Recommendations from the American Heart Association and the American College of Cardiology suggest that heart patients, especially those who have had heart attacks, refrain from driving in heavy traffic because of the stress it can cause.
These new findings give further weight to those guidelines, the researchers suggest.
"Our study provides additional rationale to avoid or reduce heavy traffic exposure after [hospital] discharge, even for those without a heart attack, since traffic exposure involves pollution exposure as well as stress," Gold said.
Gold said researchers will next have to determine the effect of pollution-related impaired heart function on inflammation, reduced oxygen flow or risk of heart arrhythmias.
