Immediate ozone effects on heart rate and repolarisation parameters in potentially susceptible individuals.

ABSTRACT

OBJECTIVES: Elevated ozone levels have been associated with cardiovascular morbidity and mortality. We investigated the effects of ozone on heart rate (HR) and repolarisation parameters in potentially susceptible populations. METHODS: Between March 2007 and December 2008, 363 ECG recordings including >2000 1 h intervals were measured in 64 individuals with type 2 diabetes or impaired glucose tolerance and in 46 healthy individuals with a potential genetic predisposition on the detoxification pathways from Augsburg, Germany. Associations between 1 h averages of ozone and HR, Bazett-corrected QT-interval (QTc), T-wave amplitude and T-wave complexity were analysed using additive mixed models. A variable indicating season and participants' location during the 1 h ECG recordings (summer and outdoors vs winter or indoors) was used as a potential ozone effect modifier. RESULTS: We observed concurrent and 1-4 h lagged increases in HR of 0.5-0.7% for each 20 µg/m(3) increase in ozone. These effects were stronger (1.0-1.2%) when participants were outdoors during the summer. We detected in all participants a concurrent (-1.31%; 95% CI -2.19% to -0.42%) and 1 h lagged (-1.32%; -2.19% to -0.45%) T-wave flattening. Elevated ozone levels were associated with 1 h (2.12%; 0.81 to 3.52) and 2 h lagged (1.89%; 0.55% to 3.26%) increases in T-wave complexity. However, no effects were seen for QTc. Ozone effects were generally more pronounced in individuals with metabolic disorders than a potential genetic predisposition. CONCLUSIONS: Changes in repolarisation might contribute to underlying pathophysiological changes associated with the link between elevated ozone levels and reported adverse cardiovascular outcomes.