Triggered activities in cat heart induced by combined administration of ouabain and calcium gluconate

The pharmacological effects of i.v. a mixture of ouabain (Oua) (50 micrograms.kg-1) and calcium gluconate (Ca2+) (100 mg.kg-1) on the electric activities of the cat hearts (n = 19) were studied by using a contact electrode and a contact electrode catheter to record both epicardial and endocardial monophasic action potentials (MAP). The results showed that the 2 drugs together reduced the MAP amplitude, decreased Vmax, and lengthened the MAP duration. Ouabain induced triggered activities, eg, early afterdepolarization, early afterhyperpolarization, delayed afterdepolarization including oscillatory afterpotentials, and triggered arrhythmias, which were enhanced by calcium gluconate. Endocardium is more sensitive than epicardium to ouabain.