A specific cardiac glycoside for cardiac failure and another for atrial fibrillation?

Ouabain produces a greater degree of prolongation of the P-R interval than digitoxin in rats when dosages which produce similar inotropic responses are used. When digitoxin is administered after pretreatment with propranolol, it produces prolongation of the P-R interval comparable to that produced by ouabain. Indications in the literature that these findings may apply to human beings suggest that in some situations atrial fibrillation may be better controlled with a hydrophilic digitalis preparation (e.g. ouabain), whereas cardiac failure with a tendency to atrioventricular block may be better controlled with a lipophilic preparation (e.g. digitoxin).