title: Controlled exposure study of air pollution and T-wave alternans in volunteers without cardiovascular disease.
abstract: 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 (O3) 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/m3), O3 (120 ppb), or combined CAP + O3 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 (TWAMax) were estimated for the first and last 5 min of each exposure (TWAMax_Early and TWAMax_Late respectively). ΔTWAMax (Late-Early) were compared among exposure groups using analysis of variance.
  
  
  RESULTS
  Mean ± SD values for ΔTWAMax were -2.1 ± 0.4, -2.7 ± 1.1, -1.9 ± 1.5, and -1.2 ± 1.5 in FA, CAP, O3, and CAP + O3 exposure groups, respectively. No significant differences were observed between pollutant exposures and FA.
  
  
  CONCLUSIONS
  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, O3, or combined CAP + O3. 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.
authors.affiliation: Division of Cardiology, Toronto General Hospital, Toronto, Ontario, Canada.
authors.forename: Marjan
authors.initials: M
authors.lastname: Kusha
authors.forename: Stephane
authors.initials: S
authors.lastname: Masse
authors.forename: Talha
authors.initials: T
authors.lastname: Farid
authors.forename: Bruce
authors.initials: B
authors.lastname: Urch
authors.forename: Frances
authors.initials: F
authors.lastname: Silverman
authors.forename: Robert D
authors.initials: RD
authors.lastname: Brook
authors.forename: Diane R
authors.initials: DR
authors.lastname: Gold
authors.forename: Iqwal
authors.initials: I
authors.lastname: Mangat
authors.forename: Mary
authors.initials: M
authors.lastname: Speck
authors.forename: Krishnakumar
authors.initials: K
authors.lastname: Nair
authors.forename: Kwaku
authors.initials: K
authors.lastname: Poku
authors.forename: Chris
authors.initials: C
authors.lastname: Meyer
authors.forename: Murray A
authors.initials: MA
authors.lastname: Mittleman
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Wellenius
authors.forename: Kumaraswamy
authors.initials: K
authors.lastname: Nanthakumar
mesh_terms: D000293:Adolescent; D000328:Adult; D000397:Air Pollution; D002318:Cardiovascular Diseases; D004781:Environmental Exposure; D005260:Female; D006801:Humans; D008297:Male; D012016:Reference Values; D055815:Young Adult