title: Concentrated ambient particles alter myocardial blood flow during acute ischemia in conscious canines.
abstract: BACKGROUND
  Experimental and observational studies have demonstrated that short-term exposure to ambient particulate matter (PM) exacerbates myocardial ischemia.
  
  
  OBJECTIVE
  We conducted this study to investigate the effects of concentrated ambient particles (CAPs) on myocardial blood flow during myocardial ischemia in chronically instrumented conscious canines.
  
  
  METHODS
  Eleven canines were instrumented with a balloon occluder around the left anterior descending coronary artery and catheters for determination of myocardial blood flow using fluorescent microspheres. Telemetric electrocardiographic and blood pressure monitoring was available for four of these animals. After recovery, we exposed animals by inhalation to 5 hr of either filtered air or CAPs (mean concentration+/-SD, 349.0+/-282.6 microg/m3) in a crossover protocol. We determined myocardial blood flow during a 5-min coronary artery occlusion immediately after each exposure. Data were analyzed using mixed models for repeated measures. The primary analysis was based on four canines that completed the protocol.
  
  
  RESULTS
  CAPs exposure decreased total myocardial blood flow during coronary artery occlusion by 0.12 mL/min/g (p<0.001) and was accompanied by a 13% (p<0.001) increase in coronary vascular resistance. Rate-pressure product, an index of myocardial oxygen demand, did not differ by exposure (p=0.90). CAPs effects on myocardial blood flow were significantly more pronounced in myocardium within or near the ischemic zone versus more remote myocardium (p interaction<0.001).
  
  
  CONCLUSIONS
  These results suggest that PM exacerbates myocardial ischemia by increased coronary vascular resistance and decreased myocardial perfusion. Further studies are needed to elucidate the mechanism of these effects.
authors.affiliation: Molecular and Integrative Physiological Sciences Program, Department of Environmental Health, Harvard School of Public Health, and Department of Pathology, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA.
authors.forename: Carlo R
authors.initials: CR
authors.lastname: Bartoli
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Wellenius
authors.forename: Brent A
authors.initials: BA
authors.lastname: Coull
authors.forename: Ichiro
authors.initials: I
authors.lastname: Akiyama
authors.forename: Edgar A
authors.initials: EA
authors.lastname: Diaz
authors.forename: Joy
authors.initials: J
authors.lastname: Lawrence
authors.forename: Kazunori
authors.initials: K
authors.lastname: Okabe
authors.forename: Richard L
authors.initials: RL
authors.lastname: Verrier
authors.forename: John J
authors.initials: JJ
authors.lastname: Godleski