Further studies on the antiarrhythmic effect of iloprost

The effect of iloprost on cardiac dysrhythmias induced by G-strophanthin and aconitine was studied in the isolated perfused whole heart, spontaneously beating right atria from rabbits and isolated whole heart, spontaneously beating atrial and ventricular strips from frog (Rana Ridibunda). The effect of iloprost on rhythm disturbances induced by warming of the bathing medium was also studied in the isolated spontaneously beating ventricular strips. Addition of iloprost to the bathing medium at the concentrations below 10(-8) M completely abolished the ectopic beating induced by different arrhythmogens used and caused a prolongation of the time for the occurrence of fibrillation. The antidysrhythmic effect of the iloprost was still continued after withdrawal of the drug from bathing medium. Iloprost itself had positive inotropic and chronotropic effects on the frog but not rabbit heart preparations with relatively higher concentrations. These concentrations of the drug produced a dysrhythmic effect which terminated within a few min after the withdrawal from the medium. A possible mechanism of action of iloprost was discussed and the validity of prostacyclin to be an endogenously occurring antiarrhythmic substance in the myocardium was emphasized.