Abstract Body (Do not enter title and authors here): Background:
Subclinical arrhythmias such as atrial high-rate episodes (AHREs) and ventricular high-rate episodes (VHREs), detected by cardiac implantable electronic devices (CIEDs), are established predictors of future cardiovascular events. While ambient air pollution has been linked to various adverse cardiovascular outcomes, limited evidence exists regarding its association with subclinical arrhythmias, especially in CIED patients. This study is the first to assess this relationship using real-time cardiac monitoring and high-resolution exposure data.

Objective:
To evaluate the association between exposure to ambient air pollutants and subclinical arrhythmias, with a specific focus on VHREs, in patients with CIEDs.

Methods:
We conducted a nationwide retrospective analysis of 225 CIED patients enrolled across eight tertiary hospitals in South Korea between 2017 and 2019. Daily exposures to PM2.5, PM10, NO2, SO2, CO, and O3 were estimated using Air Korea monitoring stations located near patient residences. Generalized Estimating Equations (GEE) were used to assess associations between pollutant exposure and the occurrence of AHREs and VHREs.

Results:
Out of 93,881 monitored episodes, 1,210 arrhythmia events were identified, comprising 1,065 AHREs and 173 VHREs. No air pollutant showed a significant association with AHREs. However, VHREs were significantly associated with NO2 exposure (OR 1.174, 95% CI 1.027–1.341). A sensitivity analysis excluding 14 patients assigned exposure based on proxy addresses due to long distances from monitoring stations showed a strengthened association (OR 1.180, 95% CI 1.030–1.351). No significant associations were observed for PM2.5, PM10, NO2, SO2, CO, and O3.
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Conclusion:
NO2 exposure was associated with an increased risk of VHREs in CIED patients. As this study was conducted prior to the COVID-19 pandemic, it provides a valuable reference for cardiovascular risk assessment under typical, unmasked air pollution conditions. These findings emphasize the importance of managing environmental risk factors and highlight the value of continuous cardiac monitoring in vulnerable populations.

Keywords: particulate matter, air pollution, arrhythmia, cardiovascular disease, AHRE, VHRE, CIED