orders are prolific sources of muscular incompetence of the mitral valve, they are also associated, either directly or indirectly, with the conditions under which organic valvular disease may arise.

Thus the differential diagnosis of mitral incompetence which is observed in a patient who presents a definite rheumatic history, and is also the subject of well-marked anæmia, or who is suffering from acute rheumatism, scarlet fever, or measles, etc., may give rise to considerable difficulty.

The recognition of the cause of the mitral insufficiency in cases of this kind rests, for the most part, on the history and general condition of the patient, taken in conjunction with the cardiac physical signs.

For instance, in the case of a patient suffering from anæmia, the differential diagnosis of incompetence of the mitral valve depends on the following considerations:

1. The history and general condition of the patient.-A history of acute rheumatism would be evidence in favour of organic disease of the mitral valve. On the other hand, well-marked pallor of the skin and mucous membranes, with no emaciation, and the absence of the signs of congestion in the pulmonic and systemic venous circulations, would point to incompetence of the valve from myocardial enfeeblement.

2. The condition of the heart and the characters of the murmur, pulmonic second sound, and pulse.—In anæmia the apex beat is seldom displaced to any great extent, the ventricular systole is not forcible, and the signs of cardiac enlargement, when present, are those of dilatation, and not of hypertrophy.

Generally speaking, a murmur due to muscular incompetence of the mitral valve follows, and does not replace, the first sound of the heart. Moreover, the bruit is usually soft and blowing in character; it is not well conducted, and is seldom heard in the left axilla, or at the angle of the left scapula. Furthermore, a murmur at the apex, due to anæmia, is almost invariably preceded and accompanied by a venous hum in the neck, and a pulmonic systolic bruit.

Accentuation of the pulmonic second sound is rarely well marked in the absence of organic disease.

The tension of the pulse is increased in many cases of anæmia, especially in the early stages of the disorder, and this is never observed in organic disease of the heart productive of incompetence of the mitral valve.

3. The effects of treatment.-Cardiac murmurs, due to anæmia, disappear under the administration of hæmatinics, so soon as the blood is restored to its normal condition, and the healthy nutrition of the cardiac muscle is re-established.

The diagnosis of the cause of the mitral insufficiency which is frequently observed during the course of an acute febrile disorder,

N

such as acute rheumatism, enteric fever, measles, etc., has already been considered under the head of "Acute Endocarditis” (see p. 146).

It turns on the period of the attack at which the apical systolic murmur is developed, and on the presence or absence of the signs and symptoms of mechanical disturbance of the circulation. In many instances, however, the solution of the problem is impossible until some time has elapsed after the subsidence of the acute process. The differentiation of the cause of the incompetence of the mitral valve, which is commonly associated with chorea, is based on considerations similar to those already indicated.

In exophthalmic goitre, again, a like method of reasoning is applicable.

The muscular and relative incompetence of the mitral valve which attends dilatation of the left ventricle from long-continued strain in cases of aortic disease and protracted high arterial tension hardly come within the scope of the present discussion, and are considered elsewhere.

Prolonged high arterial tension is a cause both of organic valvular disease and of myocardial overwork, hence it plays an important rôle in the production of mitral insufficiency. In cases of this kind it is almost impossible to determine whether the valvular incompetence is due to organic disease, or to muscular enfeeblement, or to a combination of these conditions.

A similar difficulty is frequently experienced in the differential diagnosis of the mitral insufficiency which comes on insidiously during and after middle age.

THE ESTIMATION OF THE AMOUNT OF
REGURGITATION IN MITRAL INCOMPETENCE

The estimation of the extent of the valvular lesion, or rather of the amount of blood which regurgitates into the left auricle during each systole, is based on the information derived from the following sources :—

1. The characters of the pulse.—Attention in this respect should be directed chiefly to the size and strength of the pulse and to the condition of the artery between the beats.

A small, weak and short pulse of low tension, associated with a forcible ventricular contraction, is, for obvious reasons, indicative of a considerable amount of regurgitation. On the other hand, if the artery can be felt between the beats, and the pulse is regular and of fair size, length and strength, the inference is that the amount of leakage into the auricle is slight.

2. The degree of enlargement of the left side of the heart. The position of the apex beat, the force of the impulse and the outline of dulness will enable the observer to gauge fairly accurately

the size of the left auricle and ventricle, and the strength of the ventricular contraction.

Dilatation of the auricle and ventricle is, to a certain extent, a conservative process, and provided it is not excessive, and is accompanied by adequate hypertrophy, as shown by the downward displacement of the apex beat and the force of the ventricular contraction, the lesion is probably slight.

Great enlargement of the left ventricle, especially in an outward direction, is indicative of serious regurgitation.

3. The degree of enlargement of the right ventricle. —A moderate degree of hypertrophy and dilatation of the right ventricle is com patible with an inextensive mitral lesion, provided dyspnoea is not easily excited and there is an absence of the signs of pulmonic congestion.

Great increase in the size of the right side of the heart, especially when associated with shortness of breath and other evidence of pulmonic engorgement, is indicative of serious incompetence of the mitral valve.

4. The character and conduction of the murmur and its relation to the first sound of the heart.-Neither the intensity nor the quality of the systolic apical bruit affords any criterion of the severity of the lesion, though, generally speaking, a loud or long murmur denotes that the ventricle is acting vigorously, whereas a soft or short one may indicate impending failure of the heart Nor can the manner in which the murmur is conducted be said to have much significance with respect to the estimation of the severity of the lesion. A bruit audible in the axilla and at the angle of the left scapula may accompany either slight or extensive regurgitation, but, as a rule, the greater the amount of regurgitation, the better is the murmur propagated towards the left.

It is to the effect of the murmur on the first sound of the heart that attention should be mainly directed. The more the first sound is replaced by the systolic bruit, or, in other words, the less capable the auriculo-ventricular curtains are of giving rise to the sound of tension, the more serious is the incompetence of the mitral valve.

Thus a systolic murmur heard at the apex, which follows and does not obscure the first sound and is not audible at the angle of the left scapula, denotes that the leakage through the mitral opening is slight.

On the other hand, if the first sound is totally obscured by the murmur, which is conducted into the axilla and is heard at the angle of the left scapula, the inference is that the amount of regurgitation is very considerable.

5. The degree of accentuation of the pulmonic second sound.— So long as the tricuspid valve is competent, the amount of accentuation of the pulmonic second sound forms one of the most reliable

indications of the degree of tension in the blood vessels of the lungs, and hence of the extent of the leakage through the mitral valve.

6. The severity of the symptoms.-Provided there are no complications or other extraneous exciting cause, and there is evidence on physical examination of the heart of well-developed compensatory changes, the occurrence of severe symptoms is significant of serious mitral incompetencc.

To recapitulate, the signs of an inconsiderable amount of regurgitation through the mirtral valve are: (a) a pulse of fair size, length and strength, and an artery that can be felt between the beats; (b) moderate enlargement of the left and right sides of the heart; (c) apical systolic murmur which follows and does not obscure the first sound, and is not audible at the angle of the left scapula; (d) slight accentuation of the pulmonic second sound; and (e) the absence of habitual dyspnoea, cough, etc., and of the signs of pulmonic and systemic venous congestion.

On the other hand, the signs of a large amount of leakage through the mitral opening are: (a) a small, weak, short, irregular pulse of low tension; (b) great enlargement of both sides of the heart, but more especially of the right ventricle; (c) an apical systolic murmur which wholly or partially obscures the first sound; (d) well-marked accentuation of the pulmonic second sound; and (e) habitual dyspnoea, and the signs of pulmonic and systemic venous congestion.

CHAPTER XII

MITRAL STENOSIS

Pathogenesis-Morbid anatomy-Pathological effects on the Heart and Circulation -Symptoms-Complications-Physical signs-Diagnosis-Estimation of the degree of Stenosis.

ÆTIOLOGICAL PATHOLOGY

In a large proportion of the cases, obstructive disease at the mitral orifice is the result of chronic endocarditis of rheumatic origin. Moreover, this variety of mitral disease appears to arise much more commonly in connection with the slighter manifestations of rheumatism than with the more acute forms of the disorder, a fact which goes far to explain the comparative frequency of its occurrence in childhood and early life.

Mitral stenosis has also been ascribed to congenital causes, but the weight of evidence, both pathological and clinical, is largely against this mode of origin.

In a considerable number of instances, narrowing of the mitral orifice, among adults, has been found in association with chronic renal disease and arterio-sclerosis. The relation between the valvular affection and the renal and arterial changes has not yet been satisfactorily determined.

Narrowing of the mitral aperture has been attributed to anæmia, by reason of the high systemic tension and consequent irritation to which the mitral valve is exposed in some cases of this disease.

A more likely cause of irritation of the valvular segments is the more or less constant vibration of these structures that is maintained by the to-and-fro flow of blood, which accompanies the mitral insufficiency so commonly associated with anæmia. Moreover, it is to be expected that an overgrowth of fibrous tissue in the valvular curtains and basal ring would be more readily excited in young anæmic subjects than in adults by irritation of this kind.

The more common occurrence of mitral stenosis among women than men may, in part at least, be accounted for by the fact that girls suffer from chorea and anæmia so much more frequently than boys.

The morbid process which results in narrowing of the mitral