PH\'SIOLOGIC CONSEQUENCES OF CONGENITAL HEART DISEASE 423 



of paroxysmal tachycardia. Approximately 12 per 

 cent of these cases are associated with congenital 

 heart disease. 



Abnormalities of Position 



DEXTROCARDIA. WlicH dextrocardia is associated with 

 complete situs inversus or the mirror picture of normal 

 organ arrangement, the heart is usually functionally 

 normal and anatomically a mirror image of the 

 normal. It is generally recognized that dextrocardia 

 with a mirror image of the atria and ventricles without 

 an associated situs inversus usually is a.ssociated with 

 serious intracardiac malformations. Also, the rare 

 isolated levocardia with an otherwise complete situs 

 inversus is often associated with intracardiac defects. 

 There are patients, however, without associated 

 situs inversus in whom the heart functionally is nor- 

 mal. In these instances, although the heart is on the 

 right, the relationships of the atria and ventricles are 

 normal, that is, the right atrium and right ventricle 

 are to the right of the left atrium and left ventricle, 

 and the venae cavae enter the heart on the right side. 

 In these cases the condition is usually termed "dex- 

 troversion of the heart"; the term "dextrorotorsion" 

 also has been suggested. 



COMPLETE TRANSPOSITION OF THE GRE-^iT .'ARTERIES. 



Complete transposition of the great vessels is charac- 

 terized bv origin of the aorta from the right ventricle 

 and origin of the pulmonary artery from the left 

 ventricle. The two great vessels lie parallel to each 

 other, the aorta in front of the pulmonary artery. 

 This creates a narrow vascular shadow^ in the roent- 

 genogram when the great vessels are viewed from 

 the front. 



The venous connections of the heart are normal; 

 therefore, the abnormal arterial connections lead to 

 a profound circulatory disturbance in that venous 

 blood does not have a direct route to the lungs. Un- 

 less there is some communication between the two 

 circulations, life after the umbilical cord is divided 

 is not possible. The usual communication is in the 

 form of a patent foramen ovale, a ventricular septal 

 defect, a patent ductus arteriosus, or combinations 

 of these. The bronchial arteries mav also ser\'e as a 

 route by which venous blood is carried to the lungs. 

 This malformation has a tendency to occur in males. 

 Survival beyond infancy is uncommon. 



CORRECTED TRANSPOSITION OF THE GREAT VESSELS. 



In corrected transposition of the great vessels the 



aorta communicates with the left ventricle and the 

 pulmonary artery with the right ventricle, but the 

 aorta is anterior to the pulmonary artery as it is in 

 complete transposition of the great vessels. The trans- 

 position may thus be considered as "corrected" since 

 there is no functional disturbance in spite of the 

 anatomic abnormalit\-. A ventricular septal defect 

 is usually present in corrected transposition of the 

 great vessels. In rare instances the ventricular septum 

 may be intact and there may be no other cardiac 

 abnormality; when such is the case, the patient has 

 no cardiac disability. The anatomic and hemody- 

 namic alterations found in the various forms of this 

 condition have recently been reviewed in detail by 

 Schiebler and co-workers (210). 



METHODS OF STUDY 



Clinical Methods 



The rapid increase in understanding of the pathol- 

 og\ and hemodynamics of the various forms of con- 

 genital heart disease has, in recent years, permitted a 

 much more accurate appraisal of the clinical findings 

 obtained by observation with the aid of the stetho- 

 scope, the electrocardiogram, the roentgenogram, 

 and the fiuoroscope. As a result, physicians have 

 developed to a much higher degree their ability to 

 assess, on the basis of clinical findings alone, the physi- 

 ologic and pathologic situation in patients with con- 

 genital heart disease and frequenth' are able to 

 arrive at an accurate diagnosis without recourse to 

 detailed hemodynamic studies. 



Cardiac murmurs can give insight into the presence 

 and nature of various shunts or malfunction of various 

 heart valves. The quality of the heart sounds may 

 give information concerning intracardiac and great- 

 vessel pressures; for example, an abnormally split 

 and accentuated pulmonary second sound is usually 

 due to delayed and forceful closure of the pulmonary 

 valve associated with pulmonary hypertension. In 

 some instances it is of value to study the heart sounds 

 and murmurs with a phonocardiogram, and to relate 

 the sequence of various sounds and murmurs to the 

 electrical activity of the heart by means of the simul- 

 taneously recorded electrocardiogram. The recent 

 development of intracardiac phonocardiography (161 ) 

 permits even better evaluation of the known hemo- 

 dynamic aberrations that occur in congenital heart 

 disease and provides some indication as to the site of 

 origin and hence possible causes of these murmurs. 

 Electrocardiographic studies have also proved in- 



