ARRHYTHMOGENESIS IN HUMAN RESPONSE TO PARTICULATE AIR POLLUTANTS

Abstract

ISEE-16 Introduction: Epidemiologic studies have shown that exposure to particulate matter (PM) increased arrhythmia-related mortality and morbidity. Patients with arrhythmia are also found to be more sensitive to the PM-mediated acute cardiac effects. Although these epidemiologic observations are supported by results of many animal studies, direct human data so far have only provided evidence supporting the contribution of arrhythmia to population susceptibility. Methods: We investigated whether particulate pollutants result in arrhythmogenesis in a short-term prospective study of 10 male boilermakers (age 34.3±8.1 years) with no overt cardiac diseases. They were exposed to high levels of metal particulates in their workplace. Episodes of extrasystoles within each 5-minute epoch were determined by validated algorithms across 24-hour Holter recordings. The PM2.5 (PM with aerodynamic diameter ≤2.5 um) levels were monitored concurrently using personal air samplers. Information on the time profile of daily activities was retrieved from detailed diary records. We used autoregressive logistic regression to model the probability of extrasystoles, and employed autoregressive Poisson regression to estimate the average counts of premature complexes. Supraventricular and ventricular extrasystoles were analyzed separately. Results: The cross-shift average PM2.5 level was 1.78 ± 1.25 mg/m3. Of all the recorded 5-min epochs, 7.6% (95% CI: 6.3, 9.1) had supraventricular extrasystoles and 23% (95% CI: 19, 28) had ventricular extrasystoles. Within each positive recording, the average number of extrasystoles was 1.6 (ranging from 1.3-1.9) per 5-min for supraventricular beats and 5 (ranging from 4.0 to 6.5) per 5-min for ventricular beats. We found a statistically significant association between exposures to PM2.5 and the increased extrasystole frequency. For each 1-mg/m3 increase in the preceding 4-hour average concentration of PM2.5, the associated OR was 1.82 (95% confidence interval [CI]: 1.52, 2.17) for having supraventricular extrasystoles, and the frequency of supraventricular premature beats increased by 72% (95% CI: 52, 94). For each 1-mg/m3 increase in the preceding 6-hour average concentration of PM2.5, the associated OR was 1.58 (95% CI: 1.18, 2.12) for having ventricular extrasystoles, and the frequency of ventricular premature beats increased by 21% (95% CI: 10, 32). After adjusting for circadian rhythm (morning, afternoon, evening, night), sleeping, smoking, alcohol use, coffee drinking, 5-min average heart rate, and personal coronary risk profiles, we observed a consistently positive association between PM2.5 and supraventricular extrasystoles. The adjusted analyses revealed a slightly stronger association between PM2.5 and the probability and frequency of ventricular premature complexes. Discussion: These results provide significant evidence indicating that high levels of metal particulates may induce extrasystoles in healthy working men without overt heart diseases.