Programmed electrical stimulation was performed in 12 patients with moderate to severe congestive heart failure and ventricular tachycardia (VT) to study possible arrhythmogenic properties of ibopamine, a new orally active dopamine agonist. Ibopamine induced no significant changes in spontaneous cycle length, PR, QRS, QTc, AH or HV intervals, and also right ventricular effective refractory periods were unaffected (for paced cycle lengths of 600 and 430 ms, respectively, using 1 extrastimulus: 287 ± 16 ms at baseline vs 283 ± 27 ms after ibopamine and 270 ± 23 ms during the control study vs 262 ± 19 ms after ibopamine). In 6 of the 8 patients with coronary artery disease but in none of the 4 patients with dilated cardiomyopathy, sustained VT was induced before and after ibopamine. Proarrhythmia was present in 1 patient, who became inducible after ibopamine. However, 1 patient had sustained VT only at baseline but not after ibopamine. The number of extrastimuli required for VT induction was equal (2.7 ± 0.2 vs 2.7 ± 0.2). Holter monitoring showed no changes in ventricular premature complexes, ventricular couplets and runs of VT after 1 week of ibopamine therapy. The signal-averaged electrocardiogram was abnormal in 11 and showed late potentials in 5 patients, but no changes occurred after ibopamine. During hemodynamic evaluation, increases in cardiac (32%) and stroke volume (34%) indexes were seen after administration of 100 mg of ibopamine, accompanied by a decrease in vascular resistance and filling pressures. Plasma norepinephrine decreased significantly after ibopamine (p = 0.02) but plasma epinephrine was unaffected. In conclusion, ibopamine has no significant proarrhythmic effects in patients with congestive heart failure and VT, presumably because of its favorable influence on hemodynamics and plasma norepinephrine levels.