Background: In patients with dilated cardiomyopathy and heart failure (HF) the high-dose dobutamine (DOBU) test is useful to differentiate between ischemic and non-ischemic etiology, to identify candidates for revascularization and to assess the inotropic reserve. However, HF patients are at risk of ventricular arrhythmias (VA) and the arrhythmogenic effect of DOBU may limit the test. The present study investigates whether high-dose DOBU induces VA and, if so, whether they can be predicted by 24-hour Holter and Autonomic Nervous System activation.Methods: 52 patients (age: 53 +/- 6 years) with HF and dilated cardiomyopathy (left ventricular ejection fraction: 27 +/- 5%) underwent DOBU tests because of suspected myocardial ischemia, 24 h Holter recording, baroreflex sensitivity (BRS) and RR variability (RR) analysis.Results: The mean dose was 25 +/- 8 μg/kg/min. The test was stopped because of ischemia in 14 patients; VA, in 25, bradycardia/hypotension in 2; target dose in 3; target heart rate in 2 and side effects in 6. No sustained VA occurred. VA (ventricular tachycardia, >12 ventricular couplets) were detected by 24-hour Holter in 22 patients. DOBU-induced and Holter recorded VA were significantly associated (figure) A reduced BRS and RR were not correlated with VA Conclusions: in patients with HF DOBU frequently induces non-sustained VA. There is a significant association between ''spontaneous'' VA and DOBU-induced VA. Due to the prudent interrupting criteria we used it is unknown whether VA could herald sustained VA.