Renormalization of high cardiac output and of left ventricular size following long-term recombinant human erythropoietin treatment of anemic dialyzed uremic patients. To obtain information on the effects of the correction of uremic anemia on cardiac function and size, nine normotensive dialyzed patients were studied before, during and six months after the start of i.v. treatment with recombinant human erythropoietin (rHuEPO). Pulsed-doppler echocardiographic determinations of the cardiac index (CI) and M-Mode echocardiographic estimations of the indexed left ventricular end diastolic diameter (LVEDDi), interventricular septum (IVSi), left ventricular posterior wall (LVPWi), with calculations of the left ventricular mass index (LVMi), were made on every occasion. Mean (+/- SD) hemoglobin (Hb) concentration before rHuEPO was 5.9 +/- 1.3 g/dl and rose significantly (p less than 0.0001) up to the third month, then remained constant. Baseline CI (3.4 +/- 0.6 l/min/m2bsa) was significantly higher (p less than 0.0001) than in healthy subjects (2.5 +/- 0.5 l), and decreased after the third month to a value (2.8 +/- 0.5 l) no longer different from that of controls. From pooled baseline and third month data, an inverse relationship between Hb and CI was found (p less than 0.0001). Baseline LVEDDi (32.7 +/- 4.3 mm/m2bsa), IVSi (6 +/- 1.1 mm/m2bsa) and LVPWi (5 +/- 0.8 mm/m2bsa) were all significantly higher than in controls. After three months of therapy, the only change was a decrease in LVPWi while after six months all indices, including the LVMi, decreased to values no longer higher than in controls. From pooled baseline and six months data, an inverse relationship between Hb and LVMi was found (p less than 0.0001). We conclude that treatment of uremic patients by rHuEPO is able to renormalize their already increased cardiac output soon after correction of the anemia. 