“While some studies have examined acute air pollution effects on arrhythmias, few have explored both acute and long-term effects in a mixture of components,” explains Adjani A. Peralta, PhD. “And while studies tend to focus on fine particulate matter, few have examined which specific elements of fine particulate matter can contribute to cardiovascular toxicity.”

A First-of-Its-Kind Study

Dr. Peralta and colleagues conducted the first study to investigate the association between cardiac arrhythmias and short-term exposures to fine particulate matter (PM2.5) and particle radioactivity. Results were published in Circulation. For the study, adult patients with prior implantation of a dual (atrial and ventricular) chamber ICD—but without chronic atrial fibrillation or a terminal disease—were recruited between September 2006 and March 2010. “The ICD implant provided us with an arrhythmia logbook and electrograms, which could be directly downloaded during a follow-up visit at the clinic or wirelessly via trans-telephonic transmission,” explains Dr. Peralta. “These records included information of any detected atrial or ventricular arrhythmic event and classified each episode as sustained or non-sustained.”

Study participants were assigned pollution exposures based on residential addresses, with daily PM2.5 levels estimated at 1-km×1-km grid cells from a previously validated prediction model. The association of the onset of ventricular arrhythmias (VA) with 0- to 21-day moving averages of PM2.5 and particle radioactivity (2 single-pollutant models and a 2-pollutant model) before the event was examined using time-stratified case-crossover analyses, adjusted for dew point and air temperatures.

Higher Odds of VA With Increasing Exposure

“We applied a time-stratified case-crossover analyses to demonstrate that intermediate (21-day) PM2.5 exposure was associated with higher odds of a ventricular arrhythmia event onset among patients with known cardiac disease and indication for ICD implantation independently of particle radioactivity,” says Dr. Peralta. Indeed, in a single-pollutant model of PM2.5, each interquartile range increase in daily PM2.5 levels for a 21-day moving average was associated with 39% higher odds of a VA event. Dr. Peralta adds that in models including both PM2.5 and particle radioactivity, “only the 21-day moving average of PM2.5 remained statistically significant for any of the time windows (Table). For each 3.37 µg/m3 increase in daily mean PM2.5 levels for a 21-day moving average, the odds of a VA event were 48% higher when adjusted for particle radioactivity, dew point and air temperature.”

Higher exposure to particle radioactivity was associated with higher odds of any VA event with same-day exposure and 2-day moving average prior to the event, in models adjusted for dew point and temperature. “For the 0, 2, and 3-day moving average, the increased odds were similar, except the 3-day moving average did not meet the threshold for statistical significance,” Dr. Peralta notes. “Specifically, for the 2-day moving average, there was a 13% higher odds of ventricular arrhythmic events (95% CI: 1% to 26%) for each IQR (0.08 mBq/m3) increase in particle radioactivity.”

Discussing the Association With Patients

Dr. Peralta recognizes that further studies are needed to explore if the associations seen in this study persist in healthier, younger, and more diverse populations across different regions of the US. “Studies could focus on improving models of personal exposure to different components of air pollution,” she notes. “It would be interesting to explore how multiple PM2.5 components could impact the risk of ventricular arrhythmias among ICD patients.”

In the meantime, Dr. Peralta suggests cardiovascular patients and those at high risk for cardiovascular events be informed about the risks associated with air pollution and the onset of arrhythmias, adding that physicians should talk with patients about their home environment. “For patients living near a busy road, other high-traffic zones, or industrial sites that increase exposure to air pollution, physicians can suggest an air purifier for the home or office to reduce exposure levels,” she says. “I would also suggest that cardiologists, in particular, ask their patients with ICDs about their home environment and suggest ways to reduce air pollution exposure. It is also important to consider pollution levels around the home as possible risk factors for those who do not have an ICD but do experience arrhythmias. A more aggressive treatment might be necessary for patients residing in highly polluted areas.”