Dobutamine stress echocardiography (DSE) is increasingly used in patients with moderate and severe left ventricular (LV) dysfunction. However, its effect on central and peripheral hemodynamics and LV function in this patient population is not known. This study investigates the effect of dobutamine stress on LV systolic and diastolic performance and peripheral hemodynamics in 177 consecutive patients undergoing DSE. Sixty-five patients with an LV ejection fraction (EF) of < or =40% were compared with 112 patients with an EF of >40%. Compared with those with EF > 40%, patients with EF < or =40% had a faster heart rate(76 +/- 13 vs 70 +/- 13 bpm, p < 0.001), lower systolic blood pressure (127 +/- 18 vs 133 +/- 20 mm Hg, p < 0.05), lower stroke volume (60 +/- 20 vs 74 +/- 36, p = 0.01), longer LV isovolumic relaxation time (118 +/- 37 vs 108 +/- 25 msec, p < 0.05) and larger LV end-diastolic (57 +/- 9.6 vs 49 +/- 7 mm, p < 0.0001) and end-systolic (46 +/- 10 vs 32 +/- 7.9 mm, p < 0.0001) diameters. They also had a lesser increment in cardiac output (1.5 +/- 1.6 vs 3.2 +/- 4.8 L/min, p = 0.02), a smaller reduction of systolic LV size (-5.3 +/- 4.1 vs -7.0 +/- 4.3 mm, p < 0.05) and a lower propensity to LV cavity obliteration with dobutamine infusion. In conclusion, patients with an EF < or =40% have lower baseline stroke volume, systolic blood pressure, higher heart rate, and longer LV isovolumic relaxation time. They also have a smaller increase in cardiac output, a smaller reduction of LV size, and a lower propensity to LV cavity obliteration with dobutamine stress.