The effect of CT 1341, a new steroid anesthetic, on the isolated heart muscle.

IWATSUKI, N. The Effect of CT 1341, a New Steroid Anesthetic, on the Isolated Heart Muscle. Tohoku J. exp. Med., 1973, 109 (1), 69-75 A direct inotropic effect of CT 1341, a new steroid intravenous anesthetic, upon the myocardium was studied in isolated heart muscles of dogs by measurements of force-velocity relation. CT 1341 at the concentrations over 0.139 ml/100 ml caused a dose-dependent leftward shift of the force-velocity curve. The maximum velocity of muscle shortening at zero load (Vmax) was decreased progressively with increasing concentration of CT 1341. The values of Vmax at the concentrations of 0.139 ml/100 ml, 0.279 mg/100 ml and 0.556 ml/100 ml were 94.2%, 86.5% and 67.9% of the control, respectively. Peak force, maximum rate of force development and time to peak force during isometric contraction also showed a dose-dependent decrease. Isotonic net shortening, power and work on the heart muscle were decreased dose-dependently at any given load levels. These results suggest that CT 1341 exerts a direct negative inotropic effect on the myocardium. However, the values of Vmax were 98.6% and 94.2% of the control at the concentrations of 0.056 ml/100 ml and 0.139 ml/100 ml, which were considered approximately to be the range of blood concentration at the clinically recommended induction doses (0.04-0.1 ml/kg). Therefore, the negative inotropic effect of CT 1341 upon the myocardium seems to be minor when it is used within the range of these doses. CT 1341; steroid anesthetic; isolated heart muscle; force-velocity relation; inotropism