Triggering of myocardial infarction by ambient fine particle concentration, differences in response by MI severity and presence of chronic obstructive pulmonary disease

David Q. Rich, ScD,1,2 Howard M. Kipen, MD, MPH,2,3 Junfeng Zhang, PhD,1,2

Leena Kamat, MBBS, MPH,1 Alan Wilson, MD,3 John Kostis, MD,3

1.  University of Medicine and Dentistry of New Jersey, School of Public Health, Piscataway, NJ

2.  Environmental and Occupational Health Sciences Institute - Robert Wood Johnson Medical School and Rutgers University, Piscataway, NJ

3.  Robert Wood Johnson Medical School, Piscataway, NJ

Previous studies have reported increased risk of MI associated with acute increases in particulate air pollution (PM) concentrations in the hours or days before MI onset. With conflicting results, they have examined whether pre-existing diabetes or chronic obstructive pulmonary disease (COPD) confer increased susceptibility to the adverse effects of PM. However, none have evaluated whether any response to PM differs between non-subendocardial (transmural) MI’s versus subendocardial MI’s. We studied all emergency room (ER) admissions for first MI’s (2004-2006) to residents of New Jersey living within 10km of a pollutant monitoring site (N=6808). Using a time-stratified case-crossover design and conditional logistic regression models, we estimated the rate of MI associated with increased air pollutant concentrations (PM2.5, CO, NO2, SO2, and O3) in successive 24 hour periods before ER arrival, adjusting for apparent temperature. Each 10.8 ug/m3 increase in PM2.5 concentration in the 24 hours before ER arrival for MI was not associated with an increased rate of MI. However, each 10.8 µg/m3 increase was associated with an increased rate of non-subendocardial MI’s (OR=1.10; 95% CI = 1.01, 1.20; 35% of all n=6808 MI’s), but not subendocardial MI’s (OR=0.99; 95% CI = 0.94, 1.05; 65%). Moreover, this acute PM2.5 association (within 24 hours of ER arrival) was independent of previous lagged PM2.5 concentrations and other gaseous pollutant concentrations. For non-subendocardial MI’s, subjects with COPD had larger rate estimates associated with the 24 hour moving average PM2.5 concentration than those without COPD, but there was no difference between diabetics and non-diabetics. Given the changing clinical presentation of MI over the last 10 or 20 years (increasing proportion of subendocardial versus non-subendocardial MI’s over time), these findings are consistent with previous epidemiologic studies using MI data from 10-20 years ago, human panel studies reporting ST-segment depression, and animal models demonstrating decreased arterial blood flow associated with PM exposure/concentrations. Future studies should explore these and other mechanistic explanations, as well whether specific PM species are individually responsible for these findings.

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