The following are the most important of these Anomalies of the Vascular Trunks:

1. Those Affecting The Aorta

a. There may be a single arterial trunk, which may be regarded as an aorta sending off branches from different points to the lungs.

b. The aorta may be a vessel from which only the branches of the upper half of the body (and not all of these) are given off, whilst the pulmonary artery, through the ductus arteriosus, constitutes the descending aorta.

c. There may be different degrees of obstruction of the aorta, which may be either very narrow or quite closed from its origin to its point of junction with the ductus arteriosus, in which case it is supplied by the latter with blood from the pulmonary artery. The whole arterial trunk with its ramifications, - in short the whole arterial system, - is in this case frequently disproportionally narrow.

d. The aorta may originate from both ventricles, owing to a deficiency in the partition-wall between them, in which case it is deflected somewhat to the right. The pulmonary artery is in this case, either normal, or, as is frequently observed, it is obstructed, narrow, and even closed. The ductus arteriosus, if it be present, then remains open, and carries the aortic blood to the pulmonary artery.

2. Those Affecting The Pulmonary Artery

a. The trunk of the pulmonary artery is not only absent where the lungs are wanting, but even where these are present and are furnished with vessels from the aorta.

b. Obstruction of the pulmonary artery, which may be either too narrow or wholly closed, in which case the blood is conveyed to it through the ductus arteriosus from the aorta. This occurs when the right ventricle is imperfect, when the conus arteriosus ends in a cul de sac, and very commonly when the aorta originates from both ventricles.

To the above we may add:

3. Anomalies Of The Ductus Arteriosus. A. It Is Sometimes Wholly Absent

b. Besides sending several vessels to the head and upper extremities, as do also the branches of the pulmonary artery, it supplies the aorta descendens, or rather merges into it. In this case the aorta diminishes in calibre after giving off its branches, and merges as a thin vessel into the large ductus arteriosus after the latter has been curved into an aorta descendens (Kilian). This anomaly occurs either separately and independently, or conjointly with other anomalies of the vascular trunks and of the heart.

c. The most common anomaly is a defective involution of the ductus arteriosus after birth; it either remains open or even in some cases experiences a dilatation. It is, however, much more rarely open than the foramen ovale, whose patency is in general a necessary consequence of different anomalies of the heart and vascular trunks, although even here many exceptions present themselves. On the one hand, it may remain open without any palpable anomaly of the heart and vascular trunks, and on the other it may be contracted, and even closed, where such anomalies exist.

Its involution may be hindered either by the pulmonary artery or the aorta; thus it may either be entirely patent, or may exist as a mere opening closed in the direction of the pulmonary artery, but patent towards the aorta. To this class belong those cases in adults, where the ductus arteriosus forms a sac-like appendage to the aorta, and where the obliterated ostium arteriae pulmonalis has the appearance of having been reopened by violence.

When the ductus arteriosus remains patent, many causes combine to keep the foramen ovale open.

Finally, we also observe a deficiency in the formation of the valves. The auriculo-ventricular valves present various obstructions and malformations, generally in connection with a simultaneous malformation of the corresponding ventricle, or associated with a contraction or occlusion of the opening, and principally on the right side. In reference to the arterial valves those of the pulmonary artery are occasionally absent, while malformation and closure of the latter artery, a blind termination of the conns arteriosus, and an abnormal condition of the whole of the right ventricle, are simultaneously present. These valves not unfrequently assume an abnormally inflated annular form, and in some cases only two instead of three valves are observed in the pulmonary artery or in the aorta.

The valve of the foramen ovale is either wholly absent or, as we have already remarked, is imperfect in various ways. In rare cases the Eustachian valve has been found wanting. Its defective involution after birth is interesting, inasmuch as it gives rise to the imperfect closure of the foramen ovale. The Thebesian valve has been found wanting in a few cases.

Malformations per excessum affect the heart and vascular trunks in various modes and degrees, and may be referred either to a duplication, or to an arrest of development.

To the former belong -

Complete duplication of the heart, or the occurrence of two separate hearts in two distinct pericardia, or in one common pericardium, which is not unfrequent in double monsters, especially where there is duplication of the upper half of the body, while the observations on record regarding a double heart in a single body, are very few in number, and of doubtful character.

Duplication of one or more portions of the heart, or the presence of supernumerary, more or less perfectly separated cavities from which numerous vessels proceed, as if of very rare occurrence when there is only a single body. We observe, however, occasionally, in normally formed individuals, a rudimentary partition projecting, in the form of a band or amorphous mass of muscle, into one of the cavities of the heart.

A large heart, from which proceed double vessels, is found in double monsters.

To the latter belong -

The persistence of a double aorta ascendens, a cleft condition of that vessel, the persistence of a ductus arteriosus on the right side (Breschet), and the duplication of the upper as well as the lower vena cava.

The valves also occasionally exhibit an excess of formation; we have either an increase of the apices of the auriculo-ventricular valve of the right side, or supernumerary valves, or a multiplication of their apices, with perforation of the ventricular partition; or there may be four semilunar valves in the aorta or the pulmonary artery, or duplication of the Thebesian valve, etc.

2. Anomalies Of Form

These are of comparatively common occurrence, and may affect either the external form of the heart, or its internal arrangement; occasionally both varieties are simultaneously present, in which case the deviation from the normal type in the external form is dependent on the anomaly in the internal structure. These anomalies are, moreover, either congenital or acquired, the former comprising, more especially, original malformations depending upon arrest of development; and the latter, the numerous and various deviations of form developed at different periods of life, and even in the foetus, as consecutive anomalies, arising more particularly from hypertrophy and dilatation.

The most important original anomalies in the external form of the heart, are combined with and dependent on the already described important anomalies of the internal structure and of the vessels; the more unimportant may be present, associated with very trifling internal anomalies, as for instance, the patency of the foramen ovale, or even, where none of these exist, and where the internal structure is perfectly normal. To this class belong the retraction of the heart's apex - apex cordis bifi-dus, an arrest at an early stage of development - and the rounding of the apex of the heart, associated with predominant width of the whole heart, an arrest at a very advanced period of development.

This last-named form, which depends on an equality in the size and thickness of both ventricles, is often continued to late periods of extrauterine existence, and is maintained, together with the simultaneous patency of the foetal passages, by the defective development of the lungs, whose proper functions may be mechanically obstructed by the form of the sternum, as is observed in rachitis.

Among the unimportant and incidental anomalies depending, very frequently, on various degrees of contraction and rigor, we must reckon different forms of the heart which aproximate to the round type, and are either long, slender, wedge-shaped, pad-like, spirally curved, broad and obtuse, etc.

In order to avoid repetition, we would refer our readers to the sections on hypertrophies, dilatations, and textural diseases, for further and special notice of the acquired anomalies of the heart.