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

by Unknown

In explaining the occurrence of a transposition of the arterial trunks in accordance with the facts of their normal development, Rokitansky says, if the septum trunci, starting from the usual point of the little swelling on the inner surface of the common trunk, turns abnormally with its concavity forward (instead of backward as normally), and thus passes through the trunk, there will be established an anterior left aorta and a posterior right pulmonary, because the septum ventriculorum in its growth conforms to the direction of the septum trunci. Thus, another than the usual portion of the common trunk is partitioned off and placed in communication with the respective ventricles. This furnishes us with examples of transposition of the arterial trunks relatively to each other, but not transposed in relation to the ventricle into which they are implanted. The great majority of specimens of this sort with which we are acquainted—and Rokitansky knew no others—show an open septum. They are usually spoken of, therefore, as instances of "both vessels arising from the same ventricle (the right usually)," or of "aorta communicating with both ventricles, the pulmonary artery normally placed." Rokitansky assigns no reason for this deviation in the line of growth of the septum trunci across the lumen of the common trunk; in fact, he never examined a malformed heart during this stage of development. The deviation of the septum trunci, the primitive factor in this malformation—since to it the septum ventriculorum conforms its development—he accounts for by chance (deviation of formative energy). It seems much more probable, as it is always the pulmonary artery which must be reduced in size when the concavity of the septum trunci presents anteriorly (the aorta occupies the smaller area when the concavity of the septum is posterior), that the deviation of the septum trunci is due to some one of the many conditions (endo-myocarditis) which have already been pointed out as the cause of pulmonary-artery narrowing or closure; hence, another malformation of the heart can be thus traced to pulmonary obstruction, the evident cause of so many other defects.

For examples of transposition of the vessels, both relatively to each other and to the ventricles, with complete closure of the septum ventriculorum, Rokitansky also gives a satisfactory explanation. It is important to note the distinction between cases of closed and open septum. Transposition of the vessels with open septum are, as already shown, doubtful instances of transposition from one ventricle to the other, although the vessels may be transposed in relation to each other; furthermore, the mechanism which explains relative transposition of the vessels does not explain the implantation of the vessels into the improper ventricle. His explanation is that the starting-point of the little swelling from which the septum trunci forms is shifted to a point farther forward on the inner circumference of the common trunk, and at the same time has its concavity anteriorly, and as in the previous case decreasing also the area of the pulmonary artery; and thus the aorta comes more forward and to the right, and the pulmonary artery passes more to the left and backward. The septum ventriculorum, in conforming itself to the abnormal starting-point and direction of the septum trunci, must consequently pass across the common ventricular cavity in such direction that the aorta comes in connection with the pulmonary side of the heart, and the pulmonary artery with the systemic heart. Consequently, Rokitansky traces both the relative and the actual transposition of the arterial trunks to the deviation either of the direction or of the starting-point of the septum trunci. The deviation of the position of the little swelling on the inner surface of the common trunk, which Rokitansky supposes, is probably not an actual transference or misplacement of this point of formative energy, but in reality a failure of the common trunk (aortic bulb) to continue its axis-rotation, as it normally does, after the other portions have become fixed. This premature cessation of the rotation of the common trunk would leave the starting-point of the septum trunci in a more anterior position than normal, since the trunk rotates normally in a direction to bring its left side, on which the starting-point of the septum trunci is situated, more posteriorly. A pericardial inflammatory adhesion, such as Meyer pointed out for certain cases of pulmonary artery obstruction, would fix the common trunk, prevent its proper rotation, and at the same time narrow the pulmonary orifice in certain instances. In other cases, in which the pulmonary artery is found of normal size, the septum trunci may be supposed to divide the vessel in the usual direction (concavity posteriorly as normal), whilst the septum trunci commenced to grow from an abnormal position, more anteriorly and to the left than normal (through failure of rotation); hence, as the septum ventriculorum conforms to its growth, the vessels become connected with the improper ventricle; the pulmonary, however, is not found permanently narrowed, and the septum ventriculorum is completely closed. Here the cause is a failure of the common trunk to rotate on its axis, probably from an external adhesion of its periphery.

Malformations affecting primarily the Right Side of the Heart.

In classifying defects in the course of the pulmonary artery we come to—

1. Closure or narrowing of the artery, with perfect ventricular septum.

Congenital obstruction of the pulmonary artery, with closed septum, although more rare than with open septum, is nevertheless a frequent defect. Unfortunately, it is very often impossible to distinguish with certainty whether the stenosis is essentially congenital or is acquired after birth. Complete closure is the least difficult to distinguish, because this defect very soon causes death; the prognosis in a merely narrowed orifice is much more favorable. The duration of life in complete closure never extends beyond a full year, while in undoubted congenital narrowing the age of sixty-five years has been attained.

From this atresia the most striking consequence is a reduction of size of the right ventricle, increasing almost to closure. This result is so common that Peacock thought it was the law that in atresia the right ventricle reduced itself to closure, while in stenosis it dilated and became hypertrophied. This is not the law, but only a rule of very common occurrence. Instances of eccentric and concentric hypertrophy are found among the records of these cases. Great reduction of the right ventricle results probably only when the obstruction comes very soon after the completion of the septum ventriculorum—thus at a time when the ventricle is yet very small. The wasting of the right ventricle can reach a very high degree, and when it becomes very great the tricuspid orifice is also defective. The foramen ovale and the ductus arteriosus Botalli are, in complete closure, usually found open. The obstruction may come in the conus or at the valvular orifice, or the artery is found converted into a cord.

In seven cases the duration of life varied from four days to nine months.

When the stenosis does not reach a high grade, positive clinical signs are often wanting for the determination of its existence, and the difficulty becomes greater as the age of the person advances.

Clinically, we find congenital blueness with palpitation, dyspnoea, together with the physical signs of pulmonary stenosis; these symptoms, however, may make their first appearance only on the advent of some acute disease. Sometimes they come in the first month or the first year of life, or even much later. If abundant congenital compensatory changes are present, the symptoms may be postponed until further compensatory alterations become impossible; or at the narrowed orifice the development of a fresh endocarditis may determine the occurrence of symptoms. The mere increase of the body and of the mass of the blood may alter the relations of the circulation, and this disproportion may show itself with suddenness. Febrile conditions may also suddenly disorder the circulation.