Increased Nonconducted P-Wave Arrhythmias after a Single Oil Fly Ash Inhalation Exposure in Hypertensive Rats

Abstract

BackgroundExposure to combustion-derived fine particulate matter (PM) is associated with increased cardiovascular morbidity and mortality especially in individuals with cardiovascular disease, including hypertension. PM inhalation causes several adverse changes in cardiac function that are reflected in the electrocardiogram (ECG), including altered cardiac rhythm, myocardial ischemia, and reduced heart rate variability (HRV). The sensitivity and reliability of ECG-derived parameters as indicators of the cardiovascular toxicity of PM in rats are unclear.ObjectiveWe hypothesized that spontaneously hypertensive (SH) rats are more susceptible to the development of PM-induced arrhythmia, altered ECG morphology, and reduced HRV than are Wistar Kyoto (WKY) rats, a related strain with normal blood pressure.MethodsWe exposed rats once by nose-only inhalation for 4 hr to residual oil fly ash (ROFA), an emission source particle rich in transition metals, or to air and then sacrificed them 1 or 48 hr later.ResultsROFA-exposed SH rats developed nonconducted P-wave arrhythmias but no changes in ECG morphology or HRV. We found no ECG effects in ROFA-exposed WKY rats. ROFA-exposed SH rats also had greater pulmonary injury, neutrophil infiltration, and serum C-reactive protein than did ROFA-exposed WKY rats.ConclusionsThese results suggest that cardiac arrhythmias may be an early sensitive indicator of the propensity for PM inhalation to modify cardiovascular function.

The maladaptive effects of HIV protease inhibitors (lopinavir/ritonavir) on the rat heart

“…The ECG is routinely used in health care but rats and humans differ in terms of heart rate and ECG pattern. The heart rate of a rat is typically between 300-500 beats/min [75][76][77] while that of a human is around 60-100 beats/min. This can also be attributed to the fact that the human action potential duration is 5 times longer than that of a rat 71 .…”

Effect of physical restraint on the limits of thermoregulation in telemetered rats

“…The restraint device was a nose-inhalation tube (Lab Products, Seaford, DE, USA) constructed of acrylic, with an inner diameter of 7 cm; the length of the tube was reduced from 26.7 to 22.2 cm. These modified inhalation tubes are often used for nose-only inhalation studies in our facility (Farraj et al 2009). The rats were physically restrained and had little ability to move in the tube.…”

“…Physical restraint of rodents is often used in a variety of physiological and toxicological procedures. Longterm restraint is essential for a variety of air pollutant studies where the nose and mouth of the animal must be maintained in a fixed position within an exposure chamber (Narciso et al 2003;Farraj et al 2009). Long-term restraint may also be required for collecting a variety of physiological measurements and for the parenteral administration of drugs and other agents.…”

Update in Environmental and Occupational Medicine 2009

“…Coronary artery occlusion in this model was associated with a reduction in myocardial blood flow and an increase in coronary vascular resistance (33). Similar to the effects of DE and ambient PM, short-term (1-48 h) exposure to residual oil fly ash, an emission source particle rich in transition metals, caused the development of nonconducted P-wave arrhythmias in spontaneously hypertensive rats (34). Collectively, these studies suggest that ambient particle exposure might increase the propensity toward adverse cardiovascular outcomes through activation of the sympathetic nervous system.…”