Controlled Exposure Study of Air Pollution and T-Wave Alternans in Volunteers without Cardiovascular Disease

Background: Epidemiological studies have assessed T-wave alternans (TWA) as a possible mechanism of cardiac arrhythmias related to air pollution in high-risk subjects and have reported associations with increased TWA magnitude. Objective: In this controlled human exposure study, we assessed the impact of exposure to concentrated ambient particulate matter (CAP) and ozone (O(3)) on T-wave alternans in resting volunteers without preexisting cardiovascular disease. Methods: Seventeen participants without preexisting cardiovascular disease were randomized to filtered air (FA), CAP (150 μg/m(3)), O(3) (120 ppb), or combined CAP + O(3) exposures for 2 hr. Continuous electrocardiograms (ECGs) were recorded at rest and T-wave alternans (TWA) was computed by modified moving average analysis with QRS alignment for the artifact-free intervals of 20 beats along the V2 and V5 leads. Exposure-induced changes in the highest TWA magnitude (TWA(Max)) were estimated for the first and last 5 min of each exposure (TWA(Max)_Early and TWA(Max)_Late respectively). ΔTWA(Max) (Late–Early) were compared among exposure groups using analysis of variance. Results: Mean ± SD values for ΔTWA(Max) were –2.1 ± 0.4, –2.7 ± 1.1, –1.9 ± 1.5, and –1.2 ± 1.5 in FA, CAP, O(3), and CAP + O(3) exposure groups, respectively. No significant differences were observed between pollutant exposures and FA. Conclusion: In our study of 17 volunteers who had no preexisting cardiovascular disease, we did not observe significant changes in T-wave alternans after 2-hr exposures to CAP, O(3), or combined CAP + O(3). This finding, however, does not preclude the possibility of pollution-related effects on TWA at elevated heart rates, such as during exercise, or the possibility of delayed responses.