Assessment of the effect of hemodialysis on myocardial contractility is complicated by variations in loading conditions that can occur during hemodialysis and by the prevalence of coronary artery disease among patients with chronic renal failure. Therefore, we used a load-independent index of left ventricular contractility, derived from analyses of the rate corrected velocity of circumferential fiber shortening (Vcfc)-end systolic wall stress (ESWS) relationship, to study the acute effects of hemodialysis on left ventricular function in the cases of 15 pediatric patients with end-stage renal disease. Prior to dialysis, Vcfc was appropriate for ESWS (102% +/- 16% of predicted) and did not differ significantly from values obtained from a group of nine normal control subjects of similar ages (103% +/- 9% of predicted), indicating that the patients' left ventricles were functioning in a normal inotropic state. After dialysis, Vcfc increased to levels beyond those expected for ESWS (118% +/- 20% of predicted, P < .05 versus control; P < .001 versus predialysis levels), indicating that dialysis was associated with enhancement of the left ventricle's inotropic state. A statistically significant increase in plasma norepinephrine levels was also observed. However, the increase in the percentage of the predicted Vcfc did not correlate with observed changes in this inotropic agent or with dialysis-induced variations in body weight or levels of electrolytes, urea nitrogen, or creatinine, and firm conclusions regarding the identity of the factors responsible for the positive inotropic effect of hemodialysis could not be drawn.