Dilatation of the pulmonary artery from primary disease of its walls is of so rare occurrence that it may be merely mentioned. It depends on chronic endarteritis, just spoken of. Where, on the other hand, there is great pressure in the pulmonary circulation, as in marked mitral stenosis, or insufficiency, collapse, or emphysema of the lung, with great hypertrophy of the right ventricle, general dilatation of the pulmonary artery may take place. The artery has been found to be six and a half inches in circumference in a case of emphysema, the normal average being three and a half inches; the semilunar valves were insufficient, and the walls of the artery very much diminished in thickness. From this as a maximum all degrees of dilatation have been recorded, with sometimes thickening and degeneration of the coats, at others thinning with or without degeneration.
A systolic murmur has been observed over the artery when the dilatation was considerable. The second pulmonary sound is usually strengthened (unless the elasticity of the pulmonary artery is very much diminished or the blood-pressure lowered in the right ventricle by changes of its walls, or the pulsation is very quick and irregular). A circumscribed dulness on percussion has been found in a few cases at the left edge of the sternum, when the position of the heart was normal, between the second and third cartilages. Sometimes there is a double impulse, a systolic thrill, or more often a systolic pulsation, felt in this position without any perceptible dulness, the edge of the lung being retracted and the dilated artery taking its place. It is to be borne in mind, however, that this sign (impulse, thrill, or pulsation) may be present without any dilatation of the pulmonary artery or hypertrophy of the ventricle, when inflammatory contraction of the lung has occurred or the respiration is superficial, as may happen in phthisical subjects, women, feeble and anæmic individuals, pregnant women, convalescents, and persons afflicted with acute rheumatism. In such persons the pulmonary second sound frequently seems to be unusually loud when compared with the aortic second sound, without any evidence of hypertrophy of the right ventricle being present. The determination of the position of the lung establishes the diagnosis in such cases. On the other hand, a lung dilated by emphysema may interpose and completely cover the heart and pulmonary artery, which, though dilated, may thus be masked.
Aneurism of the trunk or primary branches of the pulmonary artery, on the other hand, is an exceedingly rare disease. But few cases are on record. Aneurisms may be spindle-shaped or sacculated, of moderate size, and are usually situated on the trunk. Lividity of the face, dyspnoea, cough, dysphagia, headache, pain in the chest and epigastrium, are the principal symptoms; and a systolic pulsation (sometimes also diastolic) between the second and third left ribs near the sternum, more or less prominence here, a superficial rough systolic murmur propagated to the left and upward, a purring thrill, and flatness on percussion in the same region and a little above it, are the principal physical signs which have been recorded.
But the physical signs and symptoms above enumerated are not all present in each case, nor are they when present distinctive of pulmonary aneurism. Dysphagia is mentioned in but a single case, dyspnoea is not constant, and cyanosis was at times absent. Also, the physical signs were not constant. Even if all were present they might be produced, as has been the case, by aneurism of the left wall of the aorta, infiltrated lung-tissue, or by a solid tumor lying over the vessels. The locality of the cardiac hypertrophy and dilatation aids in establishing the diagnosis. If it is on the left side of the heart, aneurism of the aorta is indicated; if it is on the right side, pulmonary aneurism. These aneurisms tend to rupture into the pericardium sooner or later.
Dissecting aneurism of the pulmonary artery has been observed once. It was of small extent.1
1 Bul. de la Soc. Anat. de Paris, 1881, pp. 589–591.
Stenosis of the Trunk or Main Branches of the Pulmonary Artery.
Narrowing of the trunk or of one of the main branches of the pulmonary artery is of very rare occurrence. It may follow compression by an aneurism of the ascending or transverse portion of the aorta, compression by tumors in the mediastinum, as from new growths or enlarged glands; it may be caused by cicatricial contraction following mediastinitis, inflammation of a portion of lung or of the bronchial glands, or it may follow disease of the coats of the artery (endarteritis).
The phenomena produced by stenosis of the trunk of the pulmonary artery are similar to those found in stenosis at the orifice, which are treated of in another place. They are anæmia of both lungs, accompanied by persistent dyspnoea with occasional exacerbations (the patient assumes a horizontal position either habitually or during the paroxysm—a fact of true diagnostic importance [Chevers], as in all other forms of disease of the heart and great vessels the patient breathes easier when the shoulders are raised. But in this the dyspnoea results from insufficiency of the supply of blood to the lungs and system generally, and hence the recumbent posture affords relief by removing the impediment of gravity, and thus promotes the supply of blood to the brain), congestion, dilatation and hypertrophy of the right side of the heart, cardiac palpitation, and finally general venous congestion. Hypertrophy of the right ventricle is shown by increase in the transverse measurement of the cardiac area of flatness and increase in the force of the cardiac impulse. The artery up to the point of constriction is dilated; the second sound is abnormally loud and accentuated. Pulsation may be felt and a systolic murmur heard in the second left intercostal space (observed in the right once), propagated upward to the neck at the left of the sternum, or heard in the interscapular space close to the spinal column.
PROGNOSIS is unfavorable.