Potentiation of the effects of enoximone by a dobutamine infusion

Enoximone is a new inotropic agent, which acts by the inhibition of the type III phosphodiesterase (PDE) enzyme. The present report describes a 81-year-old female patient with severe heart failure following aortic valve replacement. Her cardiac activity was paced. The addition of enoximone (two doses of 0.5 mg/kg) to an intravenous infusion of dobutamine (8 mcg/kg/min) and sodium nitroprusside significantly increased cardiac output (CO) from 3.2 to 3.9 l/min and decreased pulmonary artery occlusive pressure (PAOP) from 22 to 16 mmHg. Another dose of enoximone 12 h later had similar effects. However, another 12 h later, after dobutamine had been discontinued, two successive injections of 0.5 mg/kg of enoximone were totally ineffective (CO from 2.6 to 2.5 l/min, PAOP 23 mmHg). When the dobutamine infusion was restarted (at 8 mcg/kg/min), the positive effects of 0.5 mg/kg of enoximone were again present (CO from 3.0 to 3.6 l/min, PAOP from 19 to 14 mmHg). This observation underscores the therapeutic value of the combination of PDE inhibitors such as enoximone with adrenergic agents such as dobutamine in the management of severe heart failure.