RISK OF CARDIAC ARRHYTHMIAS AMONG IMPLANTED CARDIOVERTER DEFIBRILLATOR PATIENTS ASSOCIATED WITH SIX-HOUR AIR POLLUTION EXPOSURES

Abstract

In previous analyses risk of cardiac arrhythmias in cardiac patients with implanted cardioverter defibrillators (ICD) was associated with average air pollution (PM2.5 and SO2) levels on the same day. In this analysis we investigated how the risk of arrhythmias varies during the day and associations with shorter air pollution exposures. We abstracted data of 86 New England Medical Center patients with ICD devices living in the Boston metropolitan area between June 1995 and June 2002. Date and time of ICD recorded arrhythmia and therapeutic interventions were downloaded during the patients' regular clinical follow-up (on average every 3 months). Electrocardiograms for each arrhythmia were reviewed by an electrophysiologist and classified as ventricular or supra-ventricular. We divided each day into night (0–6 AM), morning (6 AM–12 PM), afternoon (12–6 PM), and evening (6 PM-12 AM). A subject-specific episode was defined as one or more ICD detected arrhythmias in that period. Hourly fine particle and gaseous pollutant and meteorological data for the Boston area were averaged over the same 6 hour periods. Risk of arrhythmias associated with air pollution was estimated by logistic regression with adjustment for season, temperature, relative humidity, day of the week, and time period within the day. 44 patients with a mean follow-up time of 3.7 years had a total of 489 ventricular cardiac episodes. The episodes had a weak diurnal pattern with 25% 29%, 27% and 19% in the morning afternoon, evening, and night periods respectively. The risk of a ventricular arrhythmia was associated with PM2.5, SO2., NO2, and CO during the same six-hour period. (PM2.5: OR = 1.17, 95% CI 1.04,1.32 for each inter-quartile range increase [8.8 ug/m3], SO2: OR = 1.20, 95% CI 1.09, 1.32 for 4.6 ppb, NO2: OR = 1.24, 95% CI 1.08,1.41 for 4.6 ppb, CO: OR = 1.25, 95% CI 1.08,1.33 for 564 ppb). Associations between arrhythmias and air pollution during time periods 6 to 30 hours back were slightly weaker. Larger effects were found for men compared to women, and for whites compared to non-whites. These results are comparable in magnitude to previously reported associations of ICD detected arrhythmias with daily air pollution episodes, but suggest that the short air pollution episodes (less than six hours) may trigger cardiac arrhythmias in these particularly susceptible populations. This study was funded by the Health Effects Institute (98-14), and the National Institute of Environmental Health Sciences (ES-00002 and ES-09825).