A Single Exposure to Particulate or Gaseous Air Pollution Increases the Risk of Aconitine-Induced Cardiac Arrhythmia in Hypertensive Rats

Abstract

Epidemiological studies demonstrate an association between arrhythmias and air pollution. Aconitine-induced cardiac arrhythmia is widely used experimentally to examine factors that alter the risk of arrhythmogenesis. In this study, Wistar-Kyoto (WKY) and spontaneously hypertensive (SH) rats acutely exposed to synthetic residual oil fly ash (s-ROFA) particles (450 mug/m(3)) were "challenged" with aconitine to examine whether a single exposure could predispose to arrhythmogenesis. Separately, SH rats were exposed to varied particulate matter (PM) concentrations (0.45, 1.0, or 3.5 mg/m(3) s-ROFA), or the irritant gas acrolein (3 ppm), to better assess the generalization of this challenge response. Rather than directly cause arrhythmias, we hypothesized that inhaled air pollutants sensitize the heart to subsequent dysrhythmic stimuli. Twenty-four hour postexposure, urethane-anesthetized rats were monitored for heart rate (HR), electrocardiogram, and blood pressure (BP). SH rats had higher baseline HR and BP and significantly longer PR intervals, QRS duration, QTc, and JTc than WKY rats. PM exposure caused a significant increase in the PR interval, QRS duration, and QTc in WKY rats but not in SH rats. Heart rate variability was significantly decreased in WKY rats after PM exposure but increased in SH rats. Cumulative dose of aconitine that triggered arrhythmias in air-exposed SH rats was lower than WKY rats and even lower for each strain postexposure. SH rats exposed to varied concentrations of PM or acrolein developed arrhythmia at significantly lower doses of aconitine than controls; however, there was no PM concentration-dependent response. In conclusion, a single exposure to air pollution may increase the sensitivity of cardiac electrical conduction to disruption. Moreover, there seem to be host factors (e.g., cardiovascular disease) that increase vulnerability to triggered arrhythmias regardless of the pollutant or its concentration.