Groups of 12 rats with or without monocrotaline treatment (MT)-induced pulmonary inflammation were exposed by inhalation to either filtered air (FA) or concentrated urban air particles (CAPs) for five hours per day on three consecutive days. Continuous electrocardiograms (EKGs) were recorded on three members of each group during exposures. CAPs concentrations were approximately 200, 600, and 150 microg/m3, respectively, on day 1, 2 and 3 of exposure. During the exposure period, one MT, FA-exposed (8.3 %) and three MT, CAPs-exposed (25%) animals expired. Continuous EKG was recorded on one of the MT rats which succumbed on the third day of CAPs exposure. Death occurred 90 minutes (min) into exposure and was preceded by an initially steady heart rate (HR) for 15 min followed by a 1inear reduction in HR from 340 to 290 beats per min over the next 60 min. Concomitant increases in PR interval, QRS duration, HR standard deviation, low frequency HR variability power, and low-to-high frequency ratio were observed. QT interval contemporaneously decreased accompanied by a decrease in T wave height, deepening of the S wave, and emergence of possible U waves. Numerous premature ventricular contractions and other dysrhythmias were noted prior to demise. To our knowledge, this is the first continuous recording of cardiac death apparently induced by inhalation of CAPs. A similar mode of death (bradycardia and dysrhythmill followed by asystole) was reported in MT animals instilled with residual oil fly-ash particles (Watkinson et al, Tox Sci 4] :209). Canines exposed to CAPs in our laboratory have also exhibited HR slowing. Furthermore, analysis of human data obtained from implantable cardiac defibrillators has associated bradycardic events with PM2.5 elevation. Cardiac conduction system dysfunction may be an important mechanism of death associated with fine particle exposure in the MT rat.
Animal-studies; Laboratory-animals; Statistical-analysis; Analytical-methods; Analytical-chemistry; Cardiovascular-function; Cardiovascular-function-tests; Cardiovascular-system-disorders; Cardiovascular-system; Particulate-dust; Particulates; Airborne-particles; Airborne-dusts; Airborne-fibers; Exposure-assessment
The Toxicologist. Society of Toxicology 38th Annual Meeting, March 14-18, 1999, New Orleans, Louisiana