SIGNS SIMULATING THOSE OF MITRAL STENOSIS

Abstract

The duplicated 2d sound is best heard with the patient lying on his left side, as in mitral stenosis. It seemed probable that this might have been due to change in the axis of the mitral orifice, with the change in position, and with this in mind a series of cadavers were examined. It was found that, relative to the long axis of the body, the blood stream issuing through the mitral orifice was directed mainly forward with an inclination of about 20[degree] downward and slightly toward the left. Therefore, with the patient lying supine, the stream flowing through the mitral orifice is projected almost directly against gravity; when he turns on his left side, it flows horizontally. The latter position would tend to accelerate blood flow from auricle to ventricle. The 2d element of the duplicated 2d sound corresponds in time to the physiological 3d heart sound, and the 2 appear to be identical. In these individuals, the duplicated 2d heart sound was generally associated with frank apical systolic murmurs or with an impure 1st sound. It is possible the systolic murmur is a "safety-valve," mitral incompetence associated with overfilling of the ventricle being comparable to the murmur heard in normal persons immediately after strenuous exertion. A murmur will only be produced when the blood, flowing through an opening of reduced size, attains a certain critical velocity. When a high degree of mitral stenosis is present, a murmur will be heard at rest, but when the stenosis is mild there may be no murmur unless the rate of blood flow is increased by exercise. Even when the mitral orifice is normal, an obstructive murmur may be produced if the rate of blood flow be sufficiently increased. In the routine examination of athletes, the 1st sound might be so modified as to be indistinguishable from the presystolic murmur and accentuated 1st sound of mitral stenosis. The sign was present in 12 out of 192 athletes examined. In athletes the auricles become hypertrophied along with the ventricles and project blood into the ventricles with sufficient speed to give rise to the presystolic murmur. An analogous situation is observed in some cases of thyrotoxicosis. In both types of individual, the erroneous diagnosis of mitral stenosis is apt to be made. When mitral stenosis is pronounced, there may be a duplicated 2d sound followed by a rumbling dias-tolic murmur, the duration of which varies with the degree of stenosis. The 2d element of the duplicated 2d sound (le claquement d''ouverture de la mitrale) in mitral stenosis has been ascribed to the vibrations of the thickened mitral valve set up by the first rush of blood from auricle to ventricle. In this respect, its mode of production is similar to that of the normal 3d heart sound. In the former, the phenomenon is due to the stenosis; in the latter, it is due to the increased rate of blood flow through a normal mitral orifice.