AMERICAN JOURNAL OF PERINATOLOGY/VOLUME 8, NUMBER 1
January 1991
ASSOCIATION OF INCREASED CARDIOTHORACIC RATIO AND INTRAUTERINE GROWTH RETARDATION Mary Ellen A. Bozynski, M.D., Fouad H. Hanafy, M.D., and Ramiro J. Hernandez, M.D.
Clinical observation suggested an association between an increased cardiothoracic ratio (CT) and growth retardation (IUGR) in the premature neonate. To investigate this hypothesis, a case-control study was performed. Study subjects included 23 cases (IUGR) and 55 control (appropriate for gestational age [AGA]) premature infants with birthweights 2000 gm or less; Apgar scores greater than 5 at 5 minutes; no congenital heart disease; no polycythemia; no toxoplasmosis, rubella, cytomegalovirus, or herpes infection. In random order, the first chest radiograph of each infant (less than 24 hours) was reviewed by a single radiologist, unaware of the infant's growth status. The CT ratio was computed after measuring the widest internal width of the bony thorax and the cardiac diameter. Mean birthweight (±1 SD) of the IUGR infants was 1161 ± 289 g and of AGA infants was 1401 ± 4 0 1 g ( p < 0.002); the mean gestational ages (±1 SD) were 33.2 ± 2 . 8 and 30.8 ± 2.5 weeks (p < 0.001). Mean CT for IUGR infants was 0.57 ± 0.07 (±1 SD) versus AGA infants, 0.51 ± 0.04 (±1 SD), p < 0.001. When the infants were stratified by growth status and CT ratio, 11 of 23 IUGR and 1 of 55 AGA infants had an increased CT ratio p < 0.0001. When birthweight and gestational age were covaried, growth status remained the best predictor of CT, p = 0.005. There is a strong association of increased CT and growth retardation in premature infants with birthweights 2000 gm or less.
Clinical observation suggested an association between intrauterine growth retardation (IUGR) and an increased cardiothoracic (CT) ratio in the neonate without congenital heart disease. A review of the literature showed that definition of the normal CT ratio in the neonate has been the subject of some controversy.1-7 Most studies have not included premature infants and have failed to differentiate between IUGR and infants appropriate for gestation age (AGA). Edwards and associates1 studied a total of 411 patients to provide normal standards for CT ratios.1 Although the majority of infants studied were term and weighed 2000 gm, a subgroup of 131 infants (mean birthweight 1584 gm and mean gestational age 31.4 wk), had clinical and radiographic evidence of respiratory distress syndrome and were radiographed within the first 24
hours of life. In this group of infants, the mean CT ratio was 0.51 (95% confidence interval: 0.45 to 0.58). No distinction was made between AGA and IUGR infants, however. To investigate the hypothesized association between an increased CT ratio and IUGR a casecontrol study was performed. SUBJECTS AND METHODS
The subjects of this study were drawn from the population of infants with birthweights equal to or less than 2000 gm because the possible association between growth retardation and increased CT ratio was first observed in neonates weighing 2000 gm or less at birth. All study subjects were admitted to the
Department of Pediatrics, Section of Newborn Services, and Department of Radiology, Section of Pediatric Radiology, University of Michigan Medical Center, Ann Arbor, MI This was a poster presentation at the meeting of the Society of Pediatric Radiology, Washington, May, 1988 Reprint requests: Dr. Bozynski, Department of Pediatrics, Section of Newborn Services, University of Michigan Medical Center, L3023 Women's Hospital, Box 0254, 200 East Drive, Ann Arbor, Michigan 48109-0254
28
Copyright © 1991 by Thieme Medical Publishers, Inc., 381 Park Avenue South, New York, NY 10016. All rights reserved.
Downloaded by: East Carolina University. Copyrighted material.
ABSTRACT
ASSOCIATION OF CARDIOTHORACIC RATIO AND lUGR/Bozynski, Hanafy, Hernandez
Table 1.
Birthweight (gm ± 1 SD) Gestational age (wk ± 1 SD) Agpar 1 minute (median [range]) Apgar 5 minutes (median [range]) Intubated Lung disease None Respiratory distress syndrome Transient tachypnea of the newborn *t(76) = 2.41. +t(76) = 4.6.
study. All tests were two tailed and p < 0.05 was assumed to be significant. RESULTS
Twenty-three IUGR and 55 AGA infants were studied. Patient characteristics are given in Table 1. Case and control infants differed for birthweight and gestational age; however, there were no differences in Apgar scores at 1 and 5 minutes. There were no significant differences between the groups in the proportions of infants who were intubated or who had radiographic evidence of lung disease at the time the radiographs were obtained. The mean CT ratios for IUGR and AGA infants were significantly different (Table 2). Eleven of the 23 IUGR infants, but only 1 of the 55 AGA infants had CT ratios >0.58 (Table 2). Thus, there was a strong association between IUGR and an increased CT ratio (odds ratio = 49.5). Because there were no clinical signs of congenital heart disease, echocardiographic studies were not performed in these infants during the first 24 hours of life. Three of the 11 IUGR infants with increased CT ratios were examined using echocardiography at greater than 1 week of age because a heart murmur was noted. One patient had a patent ductus arteriosus, one was normal, and one had a patent ductus arteriosus in association with mild tricuspid insufficiency. When cases and controls were stratified according to CT ratio, less than 0.58 versus equal to or greater than 0.58, the difference persisted (Table 1). Moreover, no AGA infant had a CT ratio greater than 0.6, whereas six IUGR infants had CT ratios that exceeded this value. The radiologist described all infants with CT of less than 0.58 as normal, between 0.58 and 0.60 as mildly enlarged, and greater than 0.60 as enlarged. Since the cases and controls differed for birthweight and gestational age, an analysis of covariance was performed with CT as the response variable, group as the predictor, and birthweight and gestational age as covariates. Growth status remained the best predictor of CT ratio. All IUGR infants with an increased CT ratio were symmetrically growth re-
Patient Characteristics
Cases (IUGR) (n = 23)
Controls (AGA) (n = 55)
1161 ± 289 33.3 ± 2.8 6 (1-9) 9 (5-9) 10 (43.5%)
1401 ± 401 30.8 ± 2.5 5 (1-9) 7 (5-9) 15 (27.3%)
12 (52.2%) 8 (34.8%) 3 (13%)
22 (40%) 26 (47.3%) 7 (12%)
January 1991
ASSOCIATION OF INCREASED CARDIOTHORACIC RATIO AND INTRAUTERINE GROWTH RETARDATION Mary Ellen A. Bozynski, M.D., Fouad H. Hanafy, M.D., and Ramiro J. Hernandez, M.D.
Clinical observation suggested an association between an increased cardiothoracic ratio (CT) and growth retardation (IUGR) in the premature neonate. To investigate this hypothesis, a case-control study was performed. Study subjects included 23 cases (IUGR) and 55 control (appropriate for gestational age [AGA]) premature infants with birthweights 2000 gm or less; Apgar scores greater than 5 at 5 minutes; no congenital heart disease; no polycythemia; no toxoplasmosis, rubella, cytomegalovirus, or herpes infection. In random order, the first chest radiograph of each infant (less than 24 hours) was reviewed by a single radiologist, unaware of the infant's growth status. The CT ratio was computed after measuring the widest internal width of the bony thorax and the cardiac diameter. Mean birthweight (±1 SD) of the IUGR infants was 1161 ± 289 g and of AGA infants was 1401 ± 4 0 1 g ( p < 0.002); the mean gestational ages (±1 SD) were 33.2 ± 2 . 8 and 30.8 ± 2.5 weeks (p < 0.001). Mean CT for IUGR infants was 0.57 ± 0.07 (±1 SD) versus AGA infants, 0.51 ± 0.04 (±1 SD), p < 0.001. When the infants were stratified by growth status and CT ratio, 11 of 23 IUGR and 1 of 55 AGA infants had an increased CT ratio p < 0.0001. When birthweight and gestational age were covaried, growth status remained the best predictor of CT, p = 0.005. There is a strong association of increased CT and growth retardation in premature infants with birthweights 2000 gm or less.
Clinical observation suggested an association between intrauterine growth retardation (IUGR) and an increased cardiothoracic (CT) ratio in the neonate without congenital heart disease. A review of the literature showed that definition of the normal CT ratio in the neonate has been the subject of some controversy.1-7 Most studies have not included premature infants and have failed to differentiate between IUGR and infants appropriate for gestation age (AGA). Edwards and associates1 studied a total of 411 patients to provide normal standards for CT ratios.1 Although the majority of infants studied were term and weighed 2000 gm, a subgroup of 131 infants (mean birthweight 1584 gm and mean gestational age 31.4 wk), had clinical and radiographic evidence of respiratory distress syndrome and were radiographed within the first 24
hours of life. In this group of infants, the mean CT ratio was 0.51 (95% confidence interval: 0.45 to 0.58). No distinction was made between AGA and IUGR infants, however. To investigate the hypothesized association between an increased CT ratio and IUGR a casecontrol study was performed. SUBJECTS AND METHODS
The subjects of this study were drawn from the population of infants with birthweights equal to or less than 2000 gm because the possible association between growth retardation and increased CT ratio was first observed in neonates weighing 2000 gm or less at birth. All study subjects were admitted to the
Department of Pediatrics, Section of Newborn Services, and Department of Radiology, Section of Pediatric Radiology, University of Michigan Medical Center, Ann Arbor, MI This was a poster presentation at the meeting of the Society of Pediatric Radiology, Washington, May, 1988 Reprint requests: Dr. Bozynski, Department of Pediatrics, Section of Newborn Services, University of Michigan Medical Center, L3023 Women's Hospital, Box 0254, 200 East Drive, Ann Arbor, Michigan 48109-0254
28
Copyright © 1991 by Thieme Medical Publishers, Inc., 381 Park Avenue South, New York, NY 10016. All rights reserved.
Downloaded by: East Carolina University. Copyrighted material.
ABSTRACT
ASSOCIATION OF CARDIOTHORACIC RATIO AND lUGR/Bozynski, Hanafy, Hernandez
Table 1.
Birthweight (gm ± 1 SD) Gestational age (wk ± 1 SD) Agpar 1 minute (median [range]) Apgar 5 minutes (median [range]) Intubated Lung disease None Respiratory distress syndrome Transient tachypnea of the newborn *t(76) = 2.41. +t(76) = 4.6.
study. All tests were two tailed and p < 0.05 was assumed to be significant. RESULTS
Twenty-three IUGR and 55 AGA infants were studied. Patient characteristics are given in Table 1. Case and control infants differed for birthweight and gestational age; however, there were no differences in Apgar scores at 1 and 5 minutes. There were no significant differences between the groups in the proportions of infants who were intubated or who had radiographic evidence of lung disease at the time the radiographs were obtained. The mean CT ratios for IUGR and AGA infants were significantly different (Table 2). Eleven of the 23 IUGR infants, but only 1 of the 55 AGA infants had CT ratios >0.58 (Table 2). Thus, there was a strong association between IUGR and an increased CT ratio (odds ratio = 49.5). Because there were no clinical signs of congenital heart disease, echocardiographic studies were not performed in these infants during the first 24 hours of life. Three of the 11 IUGR infants with increased CT ratios were examined using echocardiography at greater than 1 week of age because a heart murmur was noted. One patient had a patent ductus arteriosus, one was normal, and one had a patent ductus arteriosus in association with mild tricuspid insufficiency. When cases and controls were stratified according to CT ratio, less than 0.58 versus equal to or greater than 0.58, the difference persisted (Table 1). Moreover, no AGA infant had a CT ratio greater than 0.6, whereas six IUGR infants had CT ratios that exceeded this value. The radiologist described all infants with CT of less than 0.58 as normal, between 0.58 and 0.60 as mildly enlarged, and greater than 0.60 as enlarged. Since the cases and controls differed for birthweight and gestational age, an analysis of covariance was performed with CT as the response variable, group as the predictor, and birthweight and gestational age as covariates. Growth status remained the best predictor of CT ratio. All IUGR infants with an increased CT ratio were symmetrically growth re-
Patient Characteristics
Cases (IUGR) (n = 23)
Controls (AGA) (n = 55)
1161 ± 289 33.3 ± 2.8 6 (1-9) 9 (5-9) 10 (43.5%)
1401 ± 401 30.8 ± 2.5 5 (1-9) 7 (5-9) 15 (27.3%)
12 (52.2%) 8 (34.8%) 3 (13%)
22 (40%) 26 (47.3%) 7 (12%)
