A system of practical medicine. By American authors. Vol. 3

by Unknown

C. Ring-formed narrowing of the conus, due to a muscular band. Peacock reports this defect from a girl æt. nineteen, cyanotic from birth; the constriction was situated at the bases of the valves, and was formed by a muscular band covered by fibrous tissue, and the edges of the opening were studded with warty vegetations. The pulmonary valves were two in number, probably resulting from fusion of two of the cusps; were thickened and opaque, but smooth. The index finger could be passed between the valves. The artery was of small size, but much wider than the constriction. The aorta was dilated, and arose from both ventricles through a perforation of the septum ventriculorum. The foramen ovale was closed. The ductus art. Botalli gave free passage to a crowquill. The right side of heart showed dilatation and hypertrophy of both its cavities, and the tricuspid valve was thickened and had vegetations on its auricular aspect.

3. Simple stenosis and atresia of the pulmonary artery, with open septum ventriculorum.

This class includes malformations, with stenosis or atresia of the pulmonary artery, in which the defects occur before the completion of the ventricular septum, as the result of engorgement already described, but in which no other primary congenital defect exists; thus the separation of the pulmonary artery from the truncus arteriosus communis is completed; the auricles and ventricles are marked out by their septa, though not completely divided; the position of the aorta in relation to the pulmonary artery is either normal or more to its right; and there are no primary defects of any consequence in the other orifices of the heart. The simple stenosis or atresia of the pulmonary artery as thus defined is by far the most frequent malformation of the heart. Kussmaul has found about 90 described; among these are 26 cases of atresia.

As a rule, in partial obstruction the entire length of the artery, as far as the bifurcation, shows narrowing, but the greatest narrowing exists at the orifice of the pulmonary artery; only rarely are the orifice and the tube equally narrowed. Exceptionally, the tube has been found narrower just without the orifice, and later resumed its normal circumference. The walls are very often thin, like those of veins, and at times the vessel is shrunken. The valves are variously altered, often to a greater or less degree united, thickened, and opaque.

In complete closure two different conditions are seen; in some the artery itself to its bifurcation changes to a firm cord or thread; in others the tube is more or less narrowed and the orifice alone is closed.

As a rule, in stenosis and atresia of the pulmonary artery the conus is only moderately narrowed and its walls hypertrophied, while the sinus of the right ventricle is dilated and hypertrophied. The right auricle is dilated and hypertrophied. The tricuspid leaflets are clouded and thickened. The left ventricle is commonly small, and the wall not thicker than the dilated right ventricle. Sometimes the aortic and mitral valves suffer alterations of an inflammatory sort, probably of foetal origin. The shape and position of the heart are changed, but the size, as a whole, may not be much altered. The aorta may be widened, often to double the normal size. As to the origin of the aorta, it is often difficult to speak with certainty; its relative position to the pulmonary artery and to the body and axis of the heart is, as a rule, unchanged. Whether it is to be described as arising from one or both ventricles, or from the right one alone, depends on the posture which the septum ventriculorum assumes beneath its orifice. As a matter of fact, this relationship makes little difference to the flow of blood from the right ventricle, whose normal orifice is obstructed; provided the septal opening is sufficient, the flow of blood is secured and the hindrance to the circulation precluded. The opening in the septum ventriculorum may be only at the membranous portion, or it may also involve the adjacent muscular septum; the defect may be round or triangular, with its apex above and with smooth margins.

The foramen ovale has been found open in 39 cases out of 53. Its condition in this respect shows very great proportional variation in the different collections of cases. The open or closed condition of the foramen does not seem to depend on the degree of stenosis of the pulmonary artery itself. It depends, probably, more on the freedom of escape for the blood from both the ventricles through the aorta—probably also on the condition of the ductus arteriosus Botalli. The foramen ovale and ductus art. Bot. have been found closed much more frequently in stenosis than in atresia of the pulmonary artery, and the ductus is deficient or absent oftener in stenosis than in atresia. This absence of the ductus occurs in 13 per cent. of the cases, and tends to support Peacock's theory that narrowing of the pulmonary artery is the consequence of the defective development of that branchial arch out of which the ductus art. Botalli is formed.

It is of great interest to note the collateral circulation by which blood reaches the lungs when the pulmonary artery is closed. When the ductus arteriosus is open, the blood passes from the aorta into the ductus and the branches of the pulmonary artery become branches from it. When the ductus arteriosus is closed or very narrow, the bronchial arteries become the means of supply for the lungs, and through them the blood passes to be aërated. Branches from the coronary arteries have been found supplying a partial channel for the blood to the lungs, as well as the oesophageal, pericardial, internal mammary, and intercostal arteries.

The duration of life is often very considerable. Thirty-seven years have been attained.

4. Combined Stenosis and Atresia of the Pulmonary Artery.—Under this division are arranged other primary defects of the heart, which are found combined with stenosis and atresia of the pulmonary artery. It is very striking how frequently this artery is narrowed or closed in defects of the heart which date from the early period of foetal life, before the division of the truncus art. comm. and of the ventricles has occurred. It is only very rarely that defects from this early period show a normal width in this vessel; in the great majority it is narrowed or closed. The aorta is rarely affected in this manner. Changes in the aorta may come also, but a complete failure or great narrowness of this circulation is so difficult to overcome by a collateral circulation—more difficult than the pulmonary circulation—that life must cease in the foetus, or at least the conditions are incompatible with extra-uterine existence.