Electrophysiological effects of intravenous MDL 17.043.

MDL 17.043, a nonglycoside, noncatecholamine imidazolone derivative with phosphodiesterase inhibiting activity, has been shown to possess both positive inotropic and vasodilator properties. In the present study, the electrophysiological effects of intravenous MDL 17.043 were assessed in 10 patients undergoing programmed right atrial stimulation for diagnostic purposes. MDL 17.043 was administered as a single intravenous bolus injection of 1.5 mg/kg body weight over 4 min followed by an intravenous infusion of 0.75 mg/kg body weight over 20 min. With the dosage schedule used, the MDL 17.043 plasma levels achieved were similar to those previously reported to be associated with significant hemodynamic improvement of congestive heart failure. Electrophysiological measurements were performed before and during MDL 17.043 administration. MDL 17.043 consistently shortened basic sinus cycle length, sinus node recovery time and sinuatrial conduction time and decreased Wenckebach cycle length, atrioventricular and atrial refractoriness leading to positive chronotropic and dromotropic effects.