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Gregory A. Wellenius,¹ Brent A. Coull,² John J. Godleski,^1,3 Petros Koutrakis,¹ Kazunori Okabe,^1,4 Sara T. Savage,¹ Joy E. Lawrence,¹ G. G. Krishna Murthy,¹ and Richard L. Verrier^1,3,5

¹Department of Environmental Health and ²Department of Biostatistics, Harvard School of Public Health, Boston, Massachusetts, USA; ³Harvard Medical School, Boston, Massachusetts, USA; ⁴Thoracic Surgery Division, Brigham and Women's Hospital, Boston, Massachusetts, USA; ⁵Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA

Abstract

Short-term increases in ambient air pollution have been associated with an increased incidence of acute cardiac events. We assessed the effect of inhalation exposure to concentrated ambient particles (CAPs) on myocardial ischemia in a canine model of coronary artery occlusion. Six mongrel dogs underwent thoracotomy for implantation of a vascular occluder around the left anterior descending coronary artery and tracheostomy to facilitate particulate exposure. After recovery (5-13 weeks) , pairs of subjects were exposed for 6 hr/day on 3 or 4 consecutive days. Within each pair, one subject was randomly assigned to breathe CAPs on the second exposure day and filtered air at other times. The second subject breathed CAPs on the third exposure day and filtered air at other times. Immediately after each exposure, subjects underwent 5-min coronary artery occlusion. We determined ST-segment elevation, a measure of myocardial ischemia heart rate, and arrhythmia incidence during occlusion from continuous electrocardiograms. Exposure to CAPs (median, 285.7 ; range, 161.3-957.3 µg/m³) significantly (p = 0.007) enhanced occlusion-induced peak ST-segment elevation in precordial leads V₄ (9.4 ± 1.7 vs. 6.2 ± 0.9 mm, CAPs vs. filtered air, respectively) and V₅ (9.2 ± 1.3 vs. 7.5 ± 0.9 mm) . ST-segment elevation was significantly correlated with the silicon concentration of the particles and other crustal elements possibly associated with urban street dust (p = 0.003 for Si) . No associations were found with CAPs mass or number concentrations. Heart rate was not affected by CAPs exposure. These results suggest that exacerbation of myocardial ischemia during coronary artery occlusion may be an important mechanism of environmentally related acute cardiac events. Key words: air particles, air pollution, cardiovascular disease, ECG, myocardial ischemia. Environ Health Perspect 111:402-408 (2003) .