DPI 201-106 is a new positive inotropic agent. The cardiac electrophysiology of 16 patients was studied before and during DPI 201-106 administration (loading dose of intravenous DPI 201-106, 1·8 mg kg−1 h−1 administered over 10 min, followed by a maintenance dose of 0·2 mg kg−1 h−1). DPI 201-106 had no effect on the sinus node. The AH interval during fixed-rate atrial pacing became prolonged during DPI 201-106 infusion. There was a significant prolongation of the QT interval [QT (corrected), 417 ± 22 to 502 ± 35 ms, P<0·05; QT (atrial pacing at 600 ms), 374 ±17 to 419 ± 23 ms, P<0·05; QT (ventricular pacing at 600 ms), 409 ± 37 to 449 ± 30 ms, P<0·05]. The ventricular effective refractory period significantly prolonged during DPI 201-106 administration (242 ± 21 to 287 ± 56 ms, P < 0·05), but the supernormal-period duration decreased. The atrial effective refractory period was shortened in four patients and prolonged in one (261 ± 67 to 240 ± 53 ms, NS). The corrected atrial repolarization time (PTac) shortened significantly during DPI 210-106 infusion (479 ± 26 to 445 ± 22 ms at 20 min of the maintenance dose, P<0·05). Atrial fibrillation was initiated in five patients during DPI infusion, but no ventricular arrhythmia was provoked. These findings suggest that DPI 201-106 has novel differential electrophysiological effects on atria and ventricle
