(E) Effects On The Heart

Aneurysms affect the heart somewhat variously. The organ is frequently depressed by the mere presence of the aneurysm at its base. Room must be afforded for the increasing tumour, and as the position of the aorta forbids much movement upwards, the heart is pushed somewhat downwards. The extent of displacement will, of course, depend on the position and size of the aneurysm. Besides this, the heart often undergoes enlargement, especially the left ventricle. It is clear that in distending the aneurysm a considerable amount of the force of the left ventricle is wasted, and on principles already considered the ventricle must act more powerfully; the hypertrophy is therefore compensatory.

(F) Effects On Parts Around

The effects of the aneurysm on other parts will depend on the amount of pressure exercised, and the nature of the structures involved. An aneurysm often presses on nerves, causing primarily irritation of them and sometimes ultimately interruption and consequent loss of function. Thus aneurysms often produce violent pains, and even symptoms of angina pectoris when the nerves of the heart are pressed on. By irritation of the recurrent laryngeal nerve they may cause spasm of the laryngeal muscles, or by destroying the nerve lead to their paralysis. The various canals within the chest - the trachea, bronchi, oesophagus, veins - are often narrowed or completely obstructed, so that a great variety of symptoms is produced. When an aneurysm meets with a firm structure such as bone, it erodes it, as we have already seen. Cartilage resists more than bone, and in the case of an aneurysm coming against the vertebrae, we often find the bodies of the vertebrae deeply eroded, while the intervertebral cartilages stand prominently out between them (see Fig. 253). We may find also in an aneurysm advancing to the front of the chest the sternum and osseous ribs much eroded, while the cartilaginous ribs, almost isolated, are very little destroyed. In these cases it will be seen that as the dense structures are exposed inside the aneurysm, the proper wall of the latter is, by so much, deficient, and the sac of the aneurysm joins on to the bone round the edges of the eroded portion.

Fig. 253. - Aneurysm of aorta eroding vertebra:. The intervertebral cartilages are seen to remain prominent.

(G) Terminations Of Aneurysms

Aneurysms have somewhat various terminations, much the commonest being unfortunate. Sometimes, although very rarely, a cure results. This takes place only when the aneurysm gets completely filled with thrombus, in which case organization of the thrombus occurs with subsequent conversion of the aneurysm into a solid nodule of connective tissue. The formation of thrombi is brought about or encouraged in various ways. By acupuncture the internal surface may be so injured as to promote thrombosis. Occlusion of the artery by preventing the rapid renewal of blood encourages thrombosis. The occlusion may be brought about by ligaturing the vessel. Again the artery is sometimes pressed on by the bulging aneurysm itself, and obliterated. Or the aneurysm having burst, the blood collecting outside, by its pressure, obliterates the aneurysm.

But the majority of aneurysms are beyond the reach of surgical interference, and for the most part they continue enlarging till they lead to a fatal issue. This may be from the effects of Pressure on parts around, or upon the heart, so that death may result from hyperemia and oedema of the lungs, from general venous engorgement and oedema, from marasmus, and so on.

The aneurysm sometimes ends by Rupture, which occurs in various directions according to the circumstances of the aneurysm. It may here be said that the probability of.rupture is by no means in proportion to the size of the aneurysm A large aneurysm, by the amount of pressure it exercises, will probably, by its irritation, and by causing counter-pressure from displaced organs, produce sufficient support. When rupture occurs it is either into a cavity of the body, as the sae of the pericardium, the pleura, an auricle of the heart, etc.; or into a canal, as the trachea, bronchus, or another blood-vessel, such as the pulmonary artery; or into the substance of an organ, as the lung or brain; or among the muscles or connective tissue of a part. The mode in which the rupture comes about varies somewhat. The aneurysm may rupture into a cavity or on the surface of the body for want of support to its wall, a tear occurring by and by in the sac. Or the aneurysm may undermine a mucous membrane or the skin, and produce a necrosis, rupture occurring on the separation of the slough (as in Fig. 254). Or the aneurysm may induce inflammation of the mucous membrane, and the softened tissue may give way. Again, in the case of an aneurysm meeting an osseous structure a gap occurs in the wall of its proper sac, as mentioned above, and the edge of the sac may become detached from the bone, and so occasion a rupture. The rupture is not usually at the very first fatal; there is, to begin with, a slight leakage of blood through irregular apertures which get occasionally closed with blood-clot. But from some accidental increase of blood-pressure or other cause the aperture is enlarged, and a fatal haemorrhage is the result. Or death comes from exhaustion due to the prolonged drain and the interference with function that the aneurysm otherwise produces.

Fig. 254. - Aneurysm rupturing into bronchus. To the left and above is aorta with aneurysmal aperture exposed. To the right and below is trachea bifurcating. In right main bronchus (left in figure) is an aperture with a flap at its lower edge. This directed the blood upwards.

Aneurysms of the Ascending aorta are most liable to burst into the pericardium, but they also rupture into pleura, lung, oesophagus, vena cava superior, pulmonary artery, auricle, ventricle, or externally. Those of the Arch of the aorta rupture into the trachea or bronchi most frequently, but also into pericardium and on other neighbouring surfaces. The aneurysms of the Thoracic aorta rupture chiefly into the pleurae, but also into the oesophagus, bronchi, and lungs. Those of the Abdominal aorta mostly rupture behind the peritoneum, and enormous quantities of blood may accumulate beneath that membrane, bulging it and the abdominal contents forwards. There may be a subsequent tear of the peritoneum, and blood is, in that case, present in the abdominal cavity. Abdominal aneurysms also rupture into the left pleura, inferior vena cava, lungs, colon, pelvis of kidney, and posterior mediastinum.