Normal internal calibres of ostia of great arteries and of aortic isthmus in infants and children.

In order to obtain reference data, useful in paediatric cardiology and paediatric cardiovascular surgery, internal diameters of the ostia of the great arteries, of the aortic isthmus, and of the descending aorta were determined with the aid of calibrated probes in 46 necropsy specimens of normal hearts with great vessels. Age range was from 25 weeks of gestational age up to 9 years post partum. The method used proved to be as accurate as echocardiography in vivo. The data revealed linear correlations between body length and calibres of aortic and pulmonary ostia. The correlation between the calibres of the pulmonary and the aortic ostia was also a linear one with the pulmonary ostium being slightly larger than the aortic ostium. From the cross-sectional areas of the aortic isthmus and of the descending aorta an isthmus index was calculated which indicates the presence (and degree) or absence of a narrowing (tubular hypoplasia) of the aortic isthmus. Results show that narrowing of the aortic isthmus is inconstantly present in infants younger than 10 weeks, whereas it is always absent in infants and children older than 10 weeks. No dependence of narrowing of the aortic isthmus on developmental age attained at birth has been found.