Objective: To evaluate cardiac function in infants with congenital adrenal hyperplasia (CAH) before and after corticosteroid replacement therapy., Study Design: This prospective, case-control study included 9 infants with CAH. Cardiac function was assessed by echocardiography at presentation and after corticosteroid replacement therapy. Six term infants underwent 2 echocardiograms each and served as the control group. Data on fractional shortening (FS), rate-corrected velocity of circumferential fiber shortening (Vcf), wall stress, tissue Doppler indices, myocardial performance index, left ventricular mass, and Vcf/wall stress were obtained., Results: The infants with CAH exhibited myocardial dysfunction at baseline and lower systolic blood pressure (SBP) compared with the control group. FS, a measure of systolic contractility, differed significantly from before to after corticosteroid treatment (mean, 32.3%±4.7% pretreatment, 39.9%±5.0% posttreatment). Vcf, a preload-independent measure of cardiac contractility, also differed significantly before and after treatment (mean, 1.23±0.16 circumferences/second pretreatment, 1.45±0.22 circumferences/second posttreatment). SBP was also lower (mean, 84±9.3 mmHg) and improved with treatment (mean, 95±4.8 mmHg). The control group demonstrated no statistically significant changes in FS, Vcf, or SBP. There was a change in left ventricular mass in the control group between the 2 studies., Conclusion: Newborns with CAH have evidence for cardiac dysfunction at baseline that reverses with corticosteroid replacement therapy. These data suggest that corticosteroids play a direct role in modulating cardiac function in the newborn., (Copyright © 2013 Mosby, Inc. All rights reserved.)