Ultrafine particles induce rapid changes in repolarization in individuals with impaired glucose metabolism

摘要

Background: Considerable evidence from numerous studies has led to the consensus that particulate matter (PM) mass concentrations are associated with adverse cardiovascular effects. However, for particle number metrics such as ultrafine particles (UFP, diameter ＜0.1μm) the role is still not clear. Aims: We investigated the effects of different ambient particle mass and number metrics on repolarization parameters on an hourly basis. Methods: Sixty-four individuals with type 2 diabetes and impaired glucose tolerance participated in a panel study in Augsburg, Germany, between Mar 2007 and Dec 2008. Ambulatory ECG measurements were conducted on up to 4 occasions over up to 6 hours. Repolarization parameters (corrected QT-interval (QTc), T-wave amplitude (Tamp) and T-wave complexity (Tcomp)) were determined on an hourly basis. Hourly measurements on different particle mass and number size fractions were available from a central measurement site. Additive mixed models with a first-order autoregressive covariance structure adjusting for meteorology were applied. Effects are presented as %-change of outcome mean per interquartile range increase of the respective pollutant together with a 95%-confidence interval. Results: We observed decreases in QTc with UFP [-0.16 (-0.32; 0.00)] and especially with particle number counts of size classes 10-30nm and 30-50nm after 3 hours. Tamp also showed a decrease after 3 hours for the same size classes [for UFP: -0.92 (-1.65; -0.19)] as well as for size class 50-100nm. Moreover PM2.5 (diameter ＜2.5μm) and PM10 (diameter ＜10μm) were associated with decreases in Tamp within 3 hours. With a delay of 6 hours Tcomp increased in association with UFP [1.77 (0.26; 3.31)], as well as with particle number counts of size classes 30-50nm and 50-100nm. Conclusions: This study provides evidence suggesting very immediate effects of ultrafine particles on repolarization duration and morphology, key factors in the mechanisms of cardiac death.