Abstract 17901: Mechanisms of Increased Arrhythmic Risk Associated With Exposure to Urban Air Pollution
Introduction: An association has been observed between elevated levels of air pollution and the occurrence of cardiac arrhythmia. However, the mechanism by which air pollution results in arrhythmia has not been defined.
Hypothesis: We tested the hypothesis that exposure to concentrated ambient fine particles (CAP) and/or ozone (O3) would increase dispersion of repolarization, a known risk factor for arrhythmogenesis, by modulation of the autonomic nervous system.
Methods: Twenty five volunteers (18–50 years of age) each had four 2-hr exposures including: 150 μg/m3 CAP; 120 ppb O3; CAP+O3; and filtered air (FA). Continuous 12-lead ECG recording was analyzed to determine exposure-induced changes (Δ=5-min epochs at end-start) in spatial dispersion of repolarization assessed by the corrected T-peak to T-end (cTp-e) interval and QT dispersion (QTd). Spectral analysis of heart rate variability (HRV) was used to identify changes in autonomic tone, with the high frequency (HF) component indicating parasympathetic heart rate modulation and the low frequency (LF) to HF ratio (LF/HF) indicating the balance between sympathetic-parasympathetic tone.
Results: The ΔcTp-e increased significantly for the CAP+O3 (0.17±0.03, p<0.0001) exposure only. The increase remained significant when factoring FA (CAP+O3 — FA) as a control exposure (0.11±0.04, p=0.013). Spatial dispersion of repolarization was further verified by a significant increase in ΔQTd for CAP+O3 compared to FA (5.7±1.4, p=0.0002). When the LF/HF ratio of HRV (sympathetic-parasympathetic balance) was included as a covariate in a mixed model analysis the effect estimate was positive for both ΔcTp-e (p=0.002) and Δ QTd (p=0.038), indicating a relative increase in sympathetic tone was associated with increasing spatial dispersion of repolarization. When the HF component was included as a covariate with ΔcTp-e, the effect estimate for HF was negative (p=0.016), thus indicating a reduction in parasympathetic heart rate modulation is associated with increasing ΔcTp-e.
Conclusions: In conclusion, dispersion of cardiac repolarization was most affected by CAP+O3 and is partly mediated by increased sympathetic tone and withdrawal of parasympathetic heart rate modulation.
- © 2010 by American Heart Association, Inc.