[Electrophysiologic effects of enoximone]

Most inotropic agents risk aggravating atrial and ventricular hyperexcitability associated with cardiac failure by their catecholergic-like effects. The aim of this study was to evaluate the electrophysiological effects of a powerful inotropic agent, enoximone, and to determine whether it had any arrhythmogenic effects. Endocavitary electrophysiological studies of conduction, induction of supraventricular tachycardia (SVT) by programmed atrial stimulation up to two extrastimuli and induction of ventricular tachycardia by programmed ventricular stimulation using up to 3 extrastimuli were undertaken before and 15 minutes after an injection of 1 mg/kg of enoximone in 10 minutes followed by an infusion of 0.75 mg/kg over 20 minutes. The studies were undertaken in 14 patients with severe cardiac disease (average ejection fraction: 26%): all had complex ventricular arrhythmias on Holter monitoring but only 7 had inducible sustained VT less than 270/mn under basal conditions. The following effects were observed with enoximone: significant shortening of all parameters of conduction; no aggravation of supraventricular excitability; no significant inducible ventricular arrhythmias in subjects without inducible sustained VT under basal conditions; facilitation of induction and acceleration of VT induced in 6 of the 7 patients with inducible sustained VT under basal conditions (VT cycle shortening from 307 +/- 13 to 240 +/- 34 ms). In conclusion, enoximone has no supraventricular arrhythmogenic effects and does not facilitate the induction of ventricular arrhythmias in subjects without inducible sustained VT under basal conditions. However, it can accelerate the VT rhythm in patients who have inducible sustained VT under basal conditions.