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A single exposure to diesel exhaust increases the risk of triggered cardiac arrhythmias in conscious rats during dobutamine cardiac "stress" test.
Citation:
HAZARI, M. S., D. W. WINSETT, C. LAMB, N. HAYKAL-COATES, AND A. FARRAJ. A single exposure to diesel exhaust increases the risk of triggered cardiac arrhythmias in conscious rats during dobutamine cardiac "stress" test. Presented at Society of Toxicology (SOT) Annual Meeting, Washington, DC, March 06 - 10, 2011.
Impact/Purpose:
This study examines the heart rate response and arrhythmogenicity of SH rats following a single exposure to diesel exhaust during a dobutamine cardiac stress test. This methodology could potentially be applied to study the effects of air pollutants on the cardiovascular system.
Description:
Mild-to-moderate exercise is often used to stress the cardiovascular (CV) system of patients while monitoring them for electrocardiogram (ECG) abnormalities that may indicate underlying CV disease. We previously used dobutamine, which increases heart rate (HR) and contractility, to reveal exercise (stress)-induced cardiac electrical dysfunction in rats exposed to acrolein. In this study, we hypothesized that a single inhalation exposure to diesel exhaust (DE) would increase the risk of arrhythmia during the dobutamine "stress" test. Wistar-Kyoto (WKY) and spontaneously hypertensive (SH) rats were surgically implanted with radiotelemeters and a chronic intravenous (iv) catheter in the left jugular vein. After recovery, rats were exposed whole-body to either air or 150 ug/m3 whole DE for 4hr. One day later, intravenous dobutamine (20, 40, 80, 160 and 320ug/kg) was administered to conscious rats while ventilatory parameters and ECG were monitored continuously. Dobutamine caused a dose-dependent increase in HR in air-exposed rats, this response was potentiated in WKY and SH rats exposed to DE. DE caused an increase in baseline HR and during challenge prevented recovery of resting HR. Exposure to DE significantly increased the number of atrial premature beats, ventricular premature beats, and non-conducted P-waves triggered by the challenge in both strains relative to their controls. ST-depression was observed in all DE-exposed SH rats, but not WKY rats. In conclusion, the dobutamine stress test shows that rat strains with compromised cardiovascular systems are prone to elevated HR and arrhythmic events when compared to the healthy strain. A single exposure to a toxic air pollutant may increase the risk of triggering cardiac arrhythmias during exercise-like stress conditions. (This abstract does not reflect EPA policy)