Definition:—A narrowing of the left auriculo-ventricular orifice, due either to the disease of the tissues composing the mitral valve, or to thickening and adhesion of the surrounding structures, thus offering an impediment to the free flow of the blood from the left auricle to the left ventricle.
Etiology:—The condition is quite common in children above six years of age, and in young adults, and which occurs more frequently in females than in males. It is dependent upon inflammatory conditions, perhaps most often following acute rheumatic endocarditis. Adhesions take place between the structures of the valves often, which result in a narrowing of this orifice. The term, buttonhole slit has been applied to one form, which is quite common. This may be so small as to admit only the tip of the finger, or too small to admit even a small button. The other form is known as the funnel variety. This is not common, but it has been found as a congenital malformation. The result of these structural changes upon these tissues is that there is thickening and sclerosis, not only of the leaflets of the valve, but of the papillary muscles, and also of the chordae tendineae, so that elasticity is entirely gone, and the parts are rigid, stiff and more or less immovable. Later, there is a deposit of calcareous matter, constituting a condition of calcification, which is in no way influenced by treatment. Mitral stenosis also occurs as a direct result of that form of Bright's disease which is known as interstitial nephritis, the small, red or contracted kidney.
Symptomatology:—The symptoms, in the early stage of the disease, before the structural changes are pronounced, and while there is yet sufficient compensatory hypertrophy, are very few, and may be readily mistaken for those of mitral incompetency. There is a stitch-like pain in the region of the apex beat, and any degree of active exercise or violent exertion, will induce at first slight palpitation; later a severe palpitation, with extreme difficulty of breathing. Later this symptom becomes pronounced, and is more or less constant, and greatly increased by extreme agitation or muscular effort. The symptoms of pulmonary congestion described under regurgitation are apparent here, which, with the hemorrhage, render it extremely difficult at times to make a differential diagnosis. Or, at this time, when there is now no longer sufficient compensation, there is greatly increased tension and sometimes severe hemoptysis, and as a final result there may be pulmonary apoplexy. Occasionally there will be mild febrile manifestations, with a small, quickened and oppressed pulse easily compressible.
In early life this condition produces a slight deformity of the chest wall—a bulging at the junction of the ribs with the sternum above the epigastrium—at which area there is well defined pulsation, which is not present in the usual place nearer to the nipple. This indicates dilatation of the right ventricle. There is upon palpitation a characteristic thrill in the chest wall, which occurs just preceding the systole, more perceptible in the fifth intercostal space, though quite plainly marked in the fourth. This sign is similar to that occurring in mitral regurgitation, which must be excluded. It is more apt to be present when the patient is erect than when lying down. Another sign which also resembles that found in mitral incompetency is a peculiar heaving of the chest with the heart impulse. In addition to these signs there is pulsation in the epigastrium, or apparently in the liver, which is usually enlarged. The area of dulness is apt to extend to the right side, with something of a corresponding reduction in the dulness of the left side. This, however, is increased as the disease progresses toward a fatal termination.
Diagnosis:—But little can be said concerning specific points in the diagnosis of this disease. So closely do the symptoms resemble ihosc of mitral regurgitation that the diagnostician is apt to be confused. He must study carefully the latter disease and exclude it in the diagnosis. The very small, rapid pulse, which is sometimes even threadlike, often irregular, and usually very feeble, is one distinctive point. Anders mentions as important diagnostic features, increased precordial dulness upward and to the right, a murmur just above the normal apex beat, distinctly localized, which terminates abruptly with the systolic shock, and which is rough and vibrating in character. Also accentuation of the pulmonic sound, which is distinctly marked.
Prognosis:—The prognosis is by no means favorable; occurring in childhood, the disease is usually fatal; occurring in young, strong adults, it may last several years before any serious impression upon the health is made. Occurring in strong middle life, with proper care, the patient may live to old age and continue to a degree in active employment. It is especially dangerous in mothers at the child-bearing period, as the greatly increased tension may result in rupture of compensation and consequent death.