Constriction of the pulmonary artery with deficiency in the septum of the ventricles, so that the aorta communicates with the right ventricular cavity, is the commonest form of congenital malformation of the heart. Whether in such a case the foramen ovale and ductus arteriosus are closed or not depends, as has been said, upon the freedom with which the blood can escape from the right side of the heart through the displaced aorta. If the right ventricle is not unduly distended, and the pulmonary artery allows enough blood to get away, both these channels may become closed. In the other case, where the aorta and pulmonary artery are transposed, the septum of the ventricles is usually imperfect, and the foramen ovale and ductus arteriosus still remain open.
Sometimes the descending aorta is found to arise from the pulmonary artery, being apparently a continuation of the ductus arteriosus. In this case a small ascending aorta springs from the left ventricle to supply the head and neck by the usual vessels. The pulmonary artery communicates through an opening in the ventricular septum with the left ventricle. The foramen ovale is usually closed.
In contradistinction to the class of cases where the foetal openings re main pervious after birth is another class in which these orifices close too early, before uterine life has reached its term. If the foramen ovale is obliterated prematurely, the whole quantity of blood has to pass through the pulmonary artery and ductus arteriosus. Consequently, the right side of the heart is enormously hypertrophied while the left side is smaller than natural. In cases where the ductus arteriosus has undergone early obliteration, the aorta usually springs from the right ventricle, and this vessel commonly gives branches to the lungs, the pulmonary artery being very small and rudimentary.
Besides the varieties which have been mentioned, the congenital disease may also consist in defects in the valves, or in narrowing of the orifices of the large vessels which spring from the heart. Sometimes, as in the pre ceding cases, the defect may arise from malformation, as when the num ber of the valves is deficient or otherwise abnormal ; but it may also. be due to intra-uterine endocarditis. Inflammation, when it attacks the foetal heart, almost invariably affects the right side, which at this period of life is more active than the left. The tricuspid valve may be beaded, or the pulmonary semi-lunar valves may be more or less adherent. In many cases the three pulmonary valves are found united into a funnel-shaped dome with a small orifice at the apex, through which the blood is pro pelled with difficulty. A similar atresia of the aortic orifice is much less frequently met with. When the latter malformation exists, the arteries of the head and upper limbs are probably filled through the pulmonary artery by the ductus arteriosus.
It is possible that these inflammatory lesions may be occasionally ex cited, as Dr. Von Hoffman suggests, by extravasation into the placenta, from which limmorrhagic foci, pathological products, may be introduced through villous absorption into the foetal circulation.
Morbid Anatomy.—In addition to the malformations which have been described, the heart is always found to be greatly enlarged, especially on the right side. Moreover, morbid conditions are usually seen in other organs. There is often more or less atelectasis of the lungs, and the ex panded portions have a dark, congested appearance. The liver and spleen are not unfrequently swollen and congested ; and effusions may be found in the pleura and peritoneum. Also, morbid conditions of the brain are common. There may be congestion or inflammation or effusion ; or an abscess may be formed in its substance.
The congenital imperfections of the heart may be complicated by in flammation in or around the organ, for the original malformation, far from guarding the patient from subsequent inflammation, appears rather to prepare the way for it. We may therefore find the anatomical charac ters of endocarditis or inflammation of the pericardium.
Symptoms.—In cases of congenital heart disease the most striking symptom is the purplish or livid tint of the skin which, if the child sur vive its birth many months, rarely fails to be developed. Indeed, from this peculiarity of colour such cases are often spoken of as cases of cyano sis or " morbus cceruleus." The depth of the purple tint varies greatly in different subjects. In some it merely gives a dusky or swarthy hue to the skin. In others the eliscolouration may reach a deep purple or even almost a black colour. It is distinguishable in all parts of the body ; but is most noticeable in the cheeks, lips, and eyelids, and also in the ends of the fingers and toes. Even in the same subject the symptom is liable to variation. While the child is completely at rest the tint most nearly ap proaches the normal colouring ; but movement, especially fretfulness or anger, makes the skin darker at once. The cause of the cyanotic tint has been the subject of discussion. By Morgagni it was attributed to intense general congestion, and by Hunter to great contamination of the arterial current with unoxygenized blood. The latter view has been shown to be untenable. Cyanosis may exist without any admixture of venous and arte rial blood ; and in many cases where such admixture occurs the depth of tint is not in proportion to the amount of venous blood which is poured into the aorta. Dr. Peacock gives his support to the theory of Morgagni, and attributes the cliscolouration to stasis of blood in capillaries dilated by long-standing congestion, aided by imperfect aeration of the whole mass of the circulating fluid.