Air Pollution Can Spur Arrhythmias Soon After Exposure

Exposure to air pollution can trigger an immediate uptick in heart arrhythmias, new data from China show.

The relationships between exposure and risk, found for numerous air pollutants, were so strong that they could be seen even when calculated at an hourly level. Importantly, there were no apparent thresholds for how much exposure led to harm, meaning that even small amounts were linked to excess risk.

This “emphasizes the need for addressing air pollution as a public health concern and incorporating air pollution reduction into the prevention and intervention strategies for arrhythmia patients,” senior author Renjie Chen, PhD (Fudan University, Shanghai, China), told TCTMD in an email.

“Although the adverse effects of air pollution on arrhythmia have been reported, we were still surprised at the very prompt effects,” he added. As previously reported by TCTMD, acute exposure from air pollution also seems able to trigger MI-related death.

Chen stressed that better understanding the connection between air pollution and cardiovascular health is crucial, both to develop effective policies and to raise public awareness. “Cardiovascular disease is the leading cause of death globally, and air pollution is one of the most important modifiable risk factors for cardiovascular diseases worldwide. Due to the ubiquitous exposures, the relevant disease burden could be considerable,” he noted.

This burden is only expected to grow in tandem with climate change, predicted Chen, with rising temperatures and worsening pollution levels thanks to more wildfires, dust storms, and other extreme weather.

Rajesh Vedanthan, MD, MPH (NYU Langone Health, New York, NY), commenting on the results for TCTMD, highlighted both the size of the study—whose reach spanned nationwide across China—and its design, which enabled researchers to home in on the timing of exposure to specific pollutants and the subsequent risks of specific arrhythmias.

“It’s a really nice addition to the growing literature on the impact of air pollution on cardiovascular health,” he said.

Vedanthan, while noting that the levels of pollution in this study were “fairly high,” also highlighted the lack of a threshold effect. “Even at lower levels, there was still a demonstrable impact,” he pointed out. That’s “not to say there’s ‘no safe level,’” he added, but rather goes to show that even regions with less-severe levels than China should still take heed.

Led by Xiaowei Xue, MS (Fudan University), the study was published online today in CMAJ.

Strongest Links Seen for Nitrogen Dioxide

The researchers conducted a nationwide case-crossover study in China including 190,115 patients (mean age 64 years, with 47.1% younger than 65) who experienced acute onset of symptomatic arrhythmia (atrial fibrillation, atrial flutter, atrial and ventricular premature beats, and supraventricular tachycardia) between 2015 and 2021. The timing of onset for these events was available at an hourly level from the Chinese Cardiovascular Association Database — Chest Pain Center, which tracks 2,025 hospitals across 322 cities. For each patient, the researchers matched the case period of their arrhythmia to three or four control periods of the same hour, day of week, month, and year.

Hourly concentrations of six air pollutants, obtained from the nearest monitors to patients, also were available: fine particles (PM_2.5), coarse particles (PM_2.5-10), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), carbon monoxide (CO), and ozone (O₃). Average 24-hour concentrations of these pollutants were 34.4, 25.5, 27.5, 8.9, 0.7, and 59.0 μg/m³, respectively.

The relationships between the various arrhythmia and pollution types varied but were strongest for NO₂. Atrial flutter overall saw the greatest increases with exposure.

Risk of arrythmia generally spiked within the first few hours after exposure and then attenuated after 24 hours. The link between fine particles and atrial flutter was an exception, however, showing the strongest association at 2 days.

Atrial fibrillation was significantly increased in the first 24 hours after exposure to PM_2.5, NO₂, and CO, with percent changes of 1.7%, 3.4%, and 2.0%, respectively. Atrial flutter was significantly increased by all of the pollutants except O₃, with percent changes ranging from 8.1% to 11.4%. Premature beats rose only with NO₂, by 3.7%. All of the pollutants were linked to increases in supraventricular tachycardia, with percent changes ranging from 3.4% to 8.9%.

“Although our study was conducted in China, where exposure levels are very high, the results may still be relevant to other countries because of the ‘no threshold’ findings we observed in the exposure–response relationships,” which were “approximately linear,” the investigators note.

It is possible at the micro patient level, as well as potentially even at the macro advocacy level, to try and do what you can. Rajesh Vedanthan

Cardiologists can apply these findings in day-to-day practice, said Chen. “They can alert their patients against the potential harmful effects of air pollution on cardiovascular health, and recommend patients to take precautions on high-pollution days. These precautions may include staying indoors or limiting outdoor activity during peak pollution hours, using air filters, wearing masks, or taking prescribed medications as directed.”

For Vedanthan, the current study sparks his curiosity about exactly how the individuals were exposed to pollutants (indoor versus outdoor), what activities they were doing at the time of exposure, and whether the results could be reproduced in locales outside of China.

With an issue as large as air pollution, he said, for clinicians “it sort of feels like it’s out of our control,” with some asking: “What can we actually do?”

A sense of helplessness “is very reasonable,” Vedanthan continued. “On the other hand, it is possible at the micro patient level, as well as potentially even at the macro advocacy level, to try and do what you can.” As he and his colleagues describe in a 2018 Circulation review article, clinicians can ascertain their patients’ exposures and come up with strategies to mitigate them, and they also can try to control patients’ other CV risk factors like dyslipidemia, hypertension, and diabetes that make them more susceptible to pollution-triggered events.

Chen suggested that research can help investigators find methods to more precisely quantify exposure to air pollution, clarify how air pollution can have such a prompt effect on heart rhythm, and explore how climate change and air pollution interact to impact cardiovascular health.