Influence of heart rate on left ventricular dp/dt following 1,1,1-trichloroethane inhalation.

The effect of acute 1,1,1-trichloroethane (1,1,1-TCE) inhalation on left ventricular contractility and influence on heart rate were investigated in anesthetized dogs. In the acute inhalation experiment, a decrease in the maximum left ventricular dp/dt (peak dp/dt) was observed following inhalation of higher 1,1,1-TCE contentrations. The threshold concentration of 1,1,1-TCE that decreased peak dp/dt was approximately 0.2% in inspired air. A dose-response relationship was observed between the decrease in peak dp/dt and 1,1,1-TCE concentration. Heart rate recorded simultaneously increased with relatively low concentrations and decreased with higher concentrations. Increase or decrease in peak dp/dt was observed to be dependent on changes in heart rate induced by right atrial pacing. Thus, the degree of the decrease in peak dp/dt during pacing experiments was compared with those of nonpacing experiments. At low concentrations, peak dp/dt during pacing decreased more than in nonpacing experiments. With higher concentrations, the decreases in peak dp/dt during pacing was slightly less than in the nonpacing experiments. Heart rate may be important in regulating peak dp/dt for relatively low 1,1,1-TCE concentrations. However, the effect of heart rate on peak dp/dt is slight at higher concentrations.