The cardiothoracic ratio in AGA and SGA very low birth weight newborn infants

Abstract

Cardiothoracic (CT) ratio is a common measurement used to assess heart size in chest radiographs of pediatric patients, but no recent studies have analyzed the standards for CT ratios in very low birth weight (VLBW) infants. The aim of this study was to provide improved standards for CT ratios measured from chest radiographs of VLBW (<1500 g) infants, and to compare CT ratios between small for gestational age (SGA) and appropriate for gestational age (AGA) infants in this population. Among VLBW infants admitted to the Jacobi Medical Center NICU from 2002 to 2004, CT ratios were calculated from anteroposterior supine chest radiographs taken of 54 VLBW infants (18 SGA and 36 AGA group-matched on the basis of birthweight and sex) during the first 24 h of life. There were no significant differences between the two groups with respect to birthweight, sex, 1-min Apgar score, 5-min Apgar score, intubation status and degree of inspiration. Median GA of the SGA infants was significantly greater than the AGA infants (30 and 27 weeks, respectively; P<0.001). CT ratios among SGA infants were significantly larger than those among AGAs. Using the widest internal width of the bony thorax, the mean CT ratio among SGA and AGA infants was 0.523 and 0.479, respectively (P=0.00102). VLBW SGA infants have larger CT ratios than VLBW AGA infants, suggesting that existing standards for normal CT ratios may be inappropriate for use among SGA infants.