A method for the treatment or prophylaxis of cardiac disorders in a mammal, comprising administering to such mammal a short-acting ss-blocking compound of the formula: (FORMULA) wherein R may be lower alkyl, aryl, or aralkyl; n may be an integer from 0 to about 10; x may be an integer from 1 to 3; Ar may be substituted or unsubstituted aromatic; R u may be lower alkyl, or aralkyl; and pharmaceutically accepted salts thereof. Novel compounds possessing short acting ss-adrenergic blocking activity are also disclosed.