Researchers from the Harvard School of Public Health and colleagues from Boston area medical institutions have linked short term high pollution concentrations with an increased incidence of irregular and very dangerous heart arrhythmias among a group of cardiac patients from the greater Boston area who had implanted cardioverter defibrillators (ICD).
The findings appear in the June 1, 2005 issue of Environmental Health Perspectives.
"Particulate pollution and gaseous pollution from automobiles, diesel engines and power plants have long been associated with causing serious problems for people with heart conditions," said Doug Dockery, lead author of the study and professor of environmental epidemiology at the Harvard School of Public Health. He continued, "In this study we wanted to see if there's an increased risk of ventricular tachyarrhythmias, a very dangerous and rapid beating of the heart which can lead to sudden cardiac arrest. We monitored a group of Boston area residents at high risk of sudden cardiac death if not for their implanted defibrillators."
Between 1995 and 2002 the researchers monitored 203 Boston area patients from the Tufts University New England Medical Center who had implanted cardioverter defibrillators for episodes of tachyarrhythmias. Information on arrhythmias was recorded in the ICDs and retrieved during the patients' regular clinical follow-up visits. Air pollution levels were measured at up to10 sites in the Boston metropolitan area for ozone, carbon monoxide, sulfur and nitrogen dioxide and at the Harvard School of Public Health for fine particles.
The researchers found a significant association of air pollution with an increased risk of ventrical tachyarrhythmias among patients who had experienced any kind of arrhythmia three days prior to the episode, particularly when levels of particulate air pollution, black carbon, nitrogen dioxide (all linked with motor vehicle emissions) and sulfur dioxide (linked to power plants) were present. The finding suggests that air pollution provokes ventricular tachyarrhythmias among people with acutely predisposed conditions. The researchers calculated that the ICD patients had a risk of potentially life threatening ventricular tachyarrhythmias linked with fine particulate pollution five times higher for risk of cardiovascular death than the people in the general public. For the highest risk patients, those with a recent ventricular arrhythmia episode, the increased risk for a new ventricular tachyarrhythmias was 97 percent for each 10 microgram per cubic meter increase of particulate pollution.
Dockery added, "What we found suggests that air pollution may act in combination with electrical instability of the heart to increase the risk for ventricular tachyarrhythmias. The data that ICDs collect on episodes of arrhythmias provides a significant resource for understanding the role of air pollution in triggering these events."