Signs Simulating Those of Mitral Stenosis.

Duplication of the second heart sound at the apex, especially when this is associated with a systolic murmur, is apt to be regarded by recruiting medical boards as evidence of an organic mitral lesion. The purpose of this paper is to suggest that this sign is physiological, and to put forward a hypothesis to account for it and for certain other signs that are apt to lead to a mistaken diagnosis of mitral stenosis. In a group of 835 recruits referred to the writer by medical boards of the Ministry of Labour and National Service, a duplicated second heart sound at the apex was heard in 157; this series does not include any case in which an early diastolic murmur would be heard or a presystolic murmur could be elicited by exercise. The duplicated second sound, like the presystolic murmur of mitral stenosis, is best heard with the patient lying on his left side. As it seemed probable that this was due to the change in the axis of the mitral orifice with change of posture, the writer sought the help of Professor Wood Jones, who kindly examined a series of cadavers hardened in formalin and found that, relative to the long axis of the body, the blood stream issuing through the mitral orifice was directed mainly forwards with an inclination of about 20° downwards and slightly towards the left. Thus, with the patient lying on his back, the blood stream is flowing almost directly against gravity, whereas when he turns on his left side it is flowing horizontally. The latter position would tend to accelerate the blood flow from auricle to ventricle, and so, as will be shown later, would render conditions more favourable for duplication of the second heart sound. The second element of the duplicated second heart sound follows the closure of the semilunar valves by about 0-1 sec. It therefore corresponds in time to the physiological third heart sound; in fact the two appear to be identical. Thayer (1908) found that a third heart sound could be heard in 65 per cent of healthy young persons. He also demonstrated, experimentally in dogs, a similar sound which corresponded in time to the sudden distension of the ventricle that occurs early in diastole, and he suggested that the third heart sound was due to sudden tension of the A-V valves produced by the first rush of blood from auricle to ventricle. The physiological third heart sound is much more commonly heard in young than in older subjects. The same is true of the duplicated second sound in recruits. Table I gives the age incidence of the 157 cases in the present series as compared with the age incidence of the whole group of 835 cases among which they occurred.