B. ADVENTITIOUS SOUNDS

(a) Endocardial

1. Organic murmurs

Physical causes of

Site of production and direction of transmission
Character

Rhythm

2. Hæmic murmurs

Causes of

Site of production and direction of transmission
Character

Rhythm

(b) Exocardial

1. Friction sounds

Pericardial

Pleural

Pleuro-pericardial

2. Murmurs

Cardio-pulmonary

C. VASCULAR SOUNDS

I. Normal sounds

2. Adventitious sounds

Arterial
Venous

A. THE HEART SOUNDS AND THEIR MODIFICATIONS

The normal sounds.-The method of production of the normal sounds of the heart has already been discussed (see p. 12), and does not require any further consideration.

Before describing the position in which the sounds are heard, a brief account will be given of the mode of procedure that should be adopted in auscultating the heart.

The chest piece of the stethoscope is placed firstly over the apex beat and the region of the chest wall immediately surrounding it, which may collectively be termed the "mitral area." The instrument is then gradually advanced, obliquely upwards and outwards, into the left axilla, and thence as far as the angle of the left scapula. It is then placed upon successive points on the chest wall, in a line connecting the apex beat with the second right costal cartilage, at its junction with the sternum. The second right costal cartilage is known as the "aortic cartilage," and this region of the chest wall, with the adjacent portion of the second interspace, is called the "aortic area.' From here the stethoscope is carried upwards to the episternal notch and right side of the neck over the carotid artery,

and downwards along the right sternal edge. It is then placed close to the sternum over the second left costal cartilage, termed the "pulmonary cartilage," which with the adjacent portion of the second interspace is known as the "pulmonary area." The instrument is now carried along the left sternal edge to the base of the ensiform cartilage. The fourth and fifth left intercostal spaces, for about an inch to the left of the sternum, and the region of the chest wall immediately surrounding the base of the ensiform cartilage, are collectively termed the "tricuspid area."

FIG. 6.

M (within circle)= mitral area; A (within circle) = aortic area; T (within circle) = tricuspid area P (within circle)=pulmonary area

To distinguish between the two sounds of the heart, a finger should be put on the apex beat, or on the carotid artery in the neck, while the stethoscope is placed in the mitral area; the first sound is synchronous with the cardiac impulse or pulse wave, as the case may be.

(a) Position and Direction of Conduction of the Normal Heart Sounds

The left ventricle first sound.—The left ventricle first sound is most distinctly audible at and to the left of the apex beat. It is also heard with a variable degree of distinctness in the aortic area.

The aortic second sound.—The aortic second sound is heard best in the aortic area, but it is distinctly audible over the carotid arteries in the neck, especially on the right side, and in this situation is not liable to be confused with the pulmonic second sound. The aortic second sound can also be well heard at and to the left of the apex beat.

The pulmonic second sound.-The pulmonic second sound is heard most distinctly in the second left interspace close to the sternum. It is also plainly audible over the second left costal cartilage, and over the whole of the right ventricle. It is not normally audible at the apex of the heart.

The right ventricle first sound. -The first sound of the right ventricle is heard over the whole of the organ in relation with the chest wall, but it is most distinctly audible in the tricuspid area.

It will be noticed that the areas in which the various heart sounds are best heard do not necessarily correspond with the anatomical position of the structures producing them, and for the following reasons.

It has already been explained that the first sound of the heart is composed of a muscular and a valvular element. The muscular element of the first sound gives rise to no difficulty, as it is naturally heard most distinctly where the ventricles are in closest contact with the chest wall, and hence, in the case of the left ventricle, is most plainly audible at the apex of the heart.

The valvular element of the first sound of the left ventricle is not audible over the anatomical position of the mitral orifice, because here a considerable thickness of lung tissue, which is a bad conductor of sound, is interposed between the heart and chest wall. The valvular vibrations are, however, transmitted along the wall of the left ventricle, and are best heard at the apex of the heart, which, uncovered by lung, comes into close relation with the thoracic parietes.

For similar reasons the first sound of the right ventricle is most distinctly audible in the tricuspid area, and not directly over the site of the tricuspid valve. The left ventricle first sound is heard in the aortic area, and is conducted thither by the walls of the aorta.

With respect to the aortic second sound, it is heard most distinctly in the aortic area, where the vessel comes nearest to the surface. The vibrations due to the sudden tension of the semilunar valves are transmitted along the course of the aorta by means of the arterial wall and the contained column of blood. A similar mechanism explains the conduction of the aortic second sound into the neck, and it is transmitted to the apex of the heart by the wall of the left ventricle.

The reason that it is not heard over the site of the aortic orifice is that here the vessel is covered, not only by lung, but also by the infundibulum of the right ventricle, which interferes with the transmission of vibrations to the surface of the chest.

The pulmonary second sound is heard most distinctly over the exact anatomical position of the orifice, viz. at the upper border of the third left costal cartilage close to the sternum. The sound is transmitted upwards along the course of the vessel, as high as the second costal cartilage, and downwards by the wall of the right ventricle, to the base of the ensiform cartilage, and to within an inch of the apex beat.

(b) Character of the Normal Sounds of the Heart

The sounds of the heart are usually represented by the familiar syllables "lubb-dup," which correspond to the first and second sounds respectively. They convey the idea of sudden tension, and can be imitated by the more or less rapid stretching of longer and shorter pieces of string or membrane. The border of an ordinary pockethandkerchief answers the purpose perfectly well.

The first sound is duller, longer, and louder than the second, which is short and sharp. Normally the left ventricle first sound is duller and longer than that of the right, which is relatively short and sharp. This difference is in all probability explained by the relative preponderance of the muscular element in the production of the left ventricle first sound.

The pulmonary second sound at the base of the heart is under normal conditions louder than the aortic, but, according to some observers, this statement is open to doubt. The relative intensity of the two sounds is apparently determined largely by the age of the individual (Cabot).

(c) Rhythm of the Normal Sounds of the Heart

The relative time duration of the events composing the cardiac cycle may be stated approximately as follows:

The first sound occupies nearly three-tenths of a second. The interval between the first and second sounds one-twentieth of a second. The second sound occupies one-tenth of a second. The long silence, or in other words the diastole of the ventricles, occupies five-tenths of a second.

Under normal conditions the relative lengths of the interval between the first and second sounds, and second and first, are preserved, though the rate of the heart beats per minute may vary within very wide limits.

Position and direction of conduction.-In order to avoid subsequent repetition, it may be stated generally that the degree of distinctness with which the sounds of the heart are heard depends not only on the character of the sound, but also on the thickness of the thoracic wall, and the extent to which the organ is overlapped

etc.

by lung tissue, or by other material, such as air, fluid, solid tumours, For example, the first sound of the heart is more or less indistinct in cases of emphysema of the lungs, and of pericardial effusion or growths.

On the other hand, the sounds of the heart become more distinct in those conditions in which the organ comes nearer to the chest wall, as in retraction of the lungs, etc. Thus the pulmonary second sound may appear to be accentuated in retraction of the left lung, and similar effects are observed as regards the other sounds of the heart, under like circumstances.

These conditions are mentioned in order that due allowance may be made for them in estimating the character of the various cardiac sounds.

The left ventricle first sound.-In hypertrophy of the left ventricle, and in cases of high systemic tension, the first sound of the heart becomes less distinct, and may be quite inaudible in the aortic

area.

On the other hand, it becomes more distinct in this situation, in conditions of low arterial tension and in dilatation of the left ventricle. Apparently the character of the left ventricle first sound largely influences the degree of its conduction along the aorta.

The aortic second sound.-The aortic second sound becomes inaudible at and to the left of the apex beat, when, owing to enlargement of the right heart, the left ventricle, and with it the apex, is displaced from its normal position. This occurs in cases of mitral stenosis, though probably in this disease the weakness of the second sound also affects its conduction.

The absence of the aortic second sound over the carotid arteries in the neck depends on damage to the semilunar valves, the result of injury or disease, whereby these structures are unable to offer sufficient check to the backflow of blood towards the ventricle to produce vibrations of the aortic walls.

It will be seen, therefore, that the absence of the second sound in the neck is indicative of a considerable amount of regurgitation into the left ventricle.

The pulmonic second sound. This sound, in cases of enlargement of the right heart, may be heard as far to the left as the normal position of the apex beat, and is transmitted there by the walls of the right ventricle, which has usurped the place of the left.

In some instances of consolidation of the left upper lobe of the lung, the pulmonary second sound may be heard over a large area of the left chest.

The right ventricle first sound.-In cases of enlargement of the right ventricle, the first sound may be heard further to the left than usual.