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HANDBOOK OF PHYSIOLOGY -^ CIRCULATION I 



It is the purpose of this chapter to describe cur- 

 rently available information and concepts concerning 

 the physiologic consequences of congenital cardio- 

 vascular anomalies and to point out some of the 

 problems that remain. In addition, the techniques 

 used to carry out hemodynamic studies in these 

 patients will be discussed. First, however, a brief 

 review of the various types of congenital cardiac 

 defects will l)e presented. 



TYPES AND ANATOMY OF CONGENITAL CARDIAC DEFECTS 



No attempt will be made to discuss the embryologic 

 basis for congenital defects or to discuss in detail the 

 anatomic alterations that result. There are a number 

 of excellent books and reviews of these subjects 

 (89, 90, 150, 186). A classification of the various 

 defects with a brief discussion of their anatomic 

 alterations follows. 



The true incidence of congenital heart disease in 

 the general population at birth is not known. Fontana 

 (106) found that the average incidence of congenital 

 heart disease from necropsy material of all age groups 

 from eight institutions was i per cent. This, however, 

 may represent some degree of selection, and the true 

 incidence is probably less than this. MacMahon and 

 colleagues (171) reported that congenital heart 

 disease is found in about 0.35 per cent of all live 

 births. 



Anomalies of the Great Vessels 



ARTERIAL ANOMALIES. Coarctation. Coarctation of the 

 aorta occurs as a single malformation in approxi- 

 mately 6 per cent of congenital cardiac malformations. 

 It is characterized by a deformity of the aortic media 

 causing narrowing, usually severe, of the aortic 

 lumen. In the majority of instances the coarctation 

 is downstream to the junction of the ductus arteriosus 

 with the aorta, the ductus oijliterates normally, and 

 there is no abnormality of the pulmonary circulation. 

 A well-developed collateral circulation bypasses the 

 coarctation. Occasionally the ductus arteriosus re- 

 mains patent and may join the aorta either proximal 

 or distal to the coarctation. Occasionally the coarcta- 

 tion may occur proximal to the origin of the left 

 subclavian artery, and in tiiis instance there would 

 be a pressure difference in the two arms. Rarely 

 the coarctation may be in the usual location but with 

 the right subclavian artery arising anomalously 

 distal to the coarctation. Eighty per cent of patients 



with coarctation have a congenital i)icuspid aortic 

 valve. 



Patent ductus arteriosus. Normally the ductus arterio- 

 sus, a channel that short circuits blood from the 

 pulmonary artery to the aorta during fetal life, be- 

 comes obliterated shortly after birth. Sometimes this 

 fails to occur, giving rise to the clinical entity, patent 

 ductus arteriosus. This malformation is found in 

 approximately 8 per cent of congenital cardiac mal- 

 formations. As a consequence of the shunt from the 

 aorta to the pulmonary arterial system, there usually 

 is dilatation of the pulmonary arteries and the left 

 side of the heart. As previously mentioned, a patent 

 ductus may be associated with coarctation of the 

 aorta, the coarctation occurring either proximal or 

 distal to the ductus. Another of the more common 

 combinations of defects is patent ductus arteriosus 

 associated with a ventricular septal defect. 



J'ascular rings. Vascular rings are anomalies of the 

 aortic-arch system. A vascular ring is of consequence 

 if it interferes with the function of the trachea or the 

 esophagus; it may result in death if the obstruction 

 is not relie\'ed surgically. This is a rare anomaly, 

 which occurs in less than i per cent of all types of 

 congenital cardiovascular defects. 



The commonest types of vascular rings are a) 

 anomalous origin of the right subclavian artery as 

 the fourth branch of an otherwise normal aorta; 

 to reach its destination it must cross the midline 

 Ijehind the esophagus from left to right; b) functioning 

 double aortic arch; and c) single functioning right or 

 left aortic arch passing behind the esophagus to reach 

 the descending aorta which is on the contralateral 

 side. 



Persistent truncus arteriosus. Persistent truncus ar- 

 teriosus is a relatively uncommon defect comprising 

 less than 2 per cent of all congenital cardiovascular 

 defects. It is characterized by a single functioning 

 arterial vessel leaving the heart, and this vessel re- 

 cei\es the blood above a ventricular septal defect 

 from both ventricles. This vessel gives origin to the 

 coronary, systemic, and pulmonary circulations. The 

 pulmonary arteries may arise independently and 

 directly from the truncus arteriosus, or secondarily 

 from a main pulmonary artery that arises from the 

 truncus. In one type no pulmonary arteries as such 

 exist, the lung being supplied by bronchial arteries. 

 Fifty per cent of patients with trimcus arteriosus have 

 a right aortic arch. 



An aorticopulmonary septal defect is a variation ol 

 persistent truncus arteriosus in which only a small 

 communication exists between the ascending aorta 



