Boston, MA - Particulate and gaseous air pollution is positively associated with an increased risk of ventricular tachyarrhythmias among patients with an implantable cardioverter defibrillator (ICD), according to the results of a new study [1]. Although the association did not achieve significance, the investigators did find a statistically significant association between air pollution and an increased risk of ventricular arrhythmia among patients with an arrhythmia within the previous three days.

Publishing their findings in the June 2005 issue of the Environmental Health Perspectives Journal, lead investigator Dr Doug Dockery (Harvard Medical School, Boston, MA) and colleagues write that "these observations suggest that air pollution may act in combination with a cardiac electrical instability to increase the risk of ventricular tachyarrhythmias."

In their paper, the investigators note that a large number of epidemiologic studies have found an association between short-term episodes of increased air pollution and cardiovascular morbidity and mortality. Pollution has been implicated in the triggering of MI, arrhythmias, decompensation of heart-failure patients, and the exacerbation of myocardial ischemia. Other studies have demonstrated particulate-related changes in autonomic tone, which might increase the risk of ventricular arrhythmias in vulnerable patients, Dockery and colleagues write.

Following up on an earlier pilot study that showed an increased risk of an ICD discharge on days after elevated air-pollution concentrations, the investigators examined the effects of air pollution on the incidence of tachyarrhythmias in 203 ICD patients clinically followed between July 1995 and July 2002 at the Tufts New England Medical Center. Patients were predominantly men with an average age at implantation of 64 years.

Investigators found positive associations between ventricular-arrhythmic-episode days and mean air pollution on the same and previous days, but these associations were not statistically significant. When the analysis was restricted to approximately one quarter (164) of the 670 ventricular arrhythmias that followed a previous ventricular arrhythmia within three days, there was a significant association between air pollution and the ventricular-arrhythmic episode. For these ventricular arrhythmias within three days of a prior event, there were significant positive associations for fine particulate matter, black carbon, nitrogen dioxide, carbon dioxide, and sulfur dioxide.

The association of ventricular tachyarrhythmias with carbon monoxide, nitrogen dioxide, and black carbon suggest a link with motor-vehicle pollutants, according to investigators. They point out that sulfur oxides, indicators of pollution from power plants and other fossil-fuel combustion sources, might also play a role.