Cardiothoracic
Index
(made on upright frontal view of
chest at 72 inches during quiet breathing)
(re-drawn from Caffey J. Pediatric X-ray Diagnosis.
7th Ed. 1978, p 543)
ID = internal diameter of chest at level of right
hemidiaphragm
MRD = greatest perpendicular diameter from midline
to right heart border
MLD = greatest perpendicular diameter from midline
to left heart border
CT index = (MRD + MLD)/ID
| Age | Mean CT index | Standard Deviation X 1 | Range |
| 0-3 weeks1 | 0.55 | 0.05 | 0.65-0.45 |
| 4-7 weeks1 | 0.58 | 0.06 | 0.70-0.46 |
| 1 year1 | 0.53 | 0.04 | 0.61-0.45 |
| 1-2 years2 | 0.49 | 0.60-0.39 | |
| 2-6 years2 | 0.45 | 0.52-0.40 | |
| > 7 years3 | <0.50 | 0.50-0.40 |
Comments:
1st year of life, larger CT index due to more transverse heart position
in chest compared to older children and adults, and from data derived from
films obtained in expiratory phase of respiration.
Data in infants and young children obtained from supine films at 1.5m
distance
1. Bakwin H, Bakwin R. Body build in infants: VI.
Growth of the cardiac silhouette and the thoraco-abdominal cavity.
Am J Dis Child. 49:861, 1935
2. Maresh MM, Washburn AH. Size of the heart in healthy
children. Am J Dis Child 56:33, 1938
3. Lincoln EM, Spillman R. Studies of the hearts of normal
children: II. Roentgen ray studies. Am J Dis Child 35:791,
1928.