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 mu g/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). Delta TWA(Max) (Late Early) were compared among exposure groups using analysis of variance. RESULTS: Mean +/- SD values for Delta TWA(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.