In an autopsy material of 29 cases of the hypoplastic left heart syndrome coronary fibroelastosis was found in 1 case, endocardial fibroelastosis in 8 cases. Figures for 10 cases of the hypoplastic right heart syndrome were 6 cases of coronary fibroelastosis and 1 case of endocardial fibroelastosis. Age ranged from stillborn up to 11-1/2 months. Coronary and endocardial fibroelastosis seemed to be mutually exclusive localizations of congenital fibroelastosis since in our material they did not occur together in the same hearts. In hypoplastic right hearts coronary fibroelastosis was either restricted to the right coronary artery (right circumflex and posterior interventricular branch), or it was found also in the left coronary artery (anterior interventricular branch), with the most serve affections always being situated in the right one. In the only case of coronary fibroelastosis among the hypoplastic left hearts the condition was limited to the anterior interventricular branch of the left coronary artery which communicated with the hypoplastic left ventricle by a fistula. Coronary fibroelastosis was exclusively found in branches supplying the hypoplastic right ventricle and/or in a branch connected by a fistula to the hypoplastic left or right ventricle. Endocardial fibroelastosis was generally found in hypoplastic left ventricles with either no outflow or with severe outflow obstruction. A theory concerning the aetiology of both coronary and endocardial fibroelastosis of the hypoplastic ventricles is proposed. It is argued that development of fibroelastosis may in both localizations be caused or favoured by the coincidence of two factors: abnormal haemodynamic conditions and poor oxygenation of blood and tissues. Observations made in a reference material of 35 hypoplastic left and 24 hypoplastic right hearts were in accordance with this view.

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 wasfrom 25 weeks ofgestational 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 crosssectional 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.

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After repair of coarctation of the aorta using the technique of resection and end-to-end anastomosis, the internal diameters of the aortic isthmus and descending aorta often fail to increase. Better results seem possible with aortoplasty using the left subclavian flap technique. In order to clarify this matter, we investigated the structure of the left subclavian artery comparing it with that of the descending aorta and aortic isthmus: we studied the internal diameter, the thickness of the tunica media and the packing density of its elastic fibers in these vascular elements using a postmortem material of children with a coarctation of the aorta. The ages ranged from 4 days to 13 months with one child of 8 years. All 16 cases had one or more additional cardiac lesions. Operation had been performed in 3 children: 2 end-to-end anastomoses and one subclavian bypass of the aortic arch. Data were compared with observations on autopsy cases of children without cardiovascular abnormalities. The mean findings were that the calibers of the left subclavian artery and the descending aorta were within normal limits but that the caliber of the aortic isthmus was smaller than in normal children. The measurements on the tunica media showed that although, generally, the thickness of the media of the left subclavian artery was smaller than that of the aortic isthmus and descending aorta of the same individual, it contained relatively more elastic fibers than the matching vessels. This may indicate that the structure of the left subclavian artery is well suited to grow out as a part of the aortic arch.(ABSTRACT TRUNCATED AT 250 WORDS)