Dose-response effects of dobutamine infusion on the LV dimensions and ejection fraction (protocol #2). A: Heart rate, B LV diameters, C: septal wall, (SW). D posterior wall, (PW) E: Ejection fraction (EF) and F: relative wall thickness (RWT). Closed circles: diastolic measurements; Open circles: systolic measurements*: p > 0.05 vs. baseline. Data are presented as mean ± SEM.