Complete Text (Part 4)

and a less sudden development of tension in the curtains, as compared with normal, gives rise to a note which is of lower pitch, more lengthy duration, and is dull or muffled, as compared with the normal first sound. The thickened ventricular wall probably aids further in the production of this dull sound by hindering con- duction of the valve tension element of the sound. 2. Thinning of the wall, as in dilatation of the ven- tricle, on the other hand, owing to the quicker and less efficient contraction of the heart muscle and more in- elastic production of curtain tension, causes a note which is more abrupt and slapping and of higher pitch than the normal sound. The unusually thin walls of the ventricles probably facilitate the hearing of the valve tension element of the sound. In marked cases of dilatation of the ventricles the sound heard is probably mostly one of valvular tension, . FIRST SOUND 35 the papillary muscles contributing to this effect by losing their elastic pull on the valve curtains. 3. Any structural changes in the walls of the ventricle which (a) diminish the force of contraction, such as myo- carditis, fatty degeneration or infiltration, will diminish the loudness of the first sound; or (b) Any changes which diminish its elasticity, such as fibroid degeneration, will accentuate the sound. I1I.—Changes in blood-pressure also have an effect on the heart sounds. A high pressure, generally asso- ciated with some muscle hypertrophy or increased force of heart-beat causes a more vigorous ventricular con- traction and a louder sound than a low blood-pressure, which tends to weaken the sounds. IV.—An association of two or more of the above- mentioned factors which modify the first sound of the heart, a’ condition frequently met with in heart disease, will cause more marked changes in it. A weak or absent first sound will result from— 1. Changes in the valve curtains which interfere with, or do away with altogether, the development of tension in them at the onset of vs. The valve curtains may become so thick and stiff, forming a permanent funnel- shaped passage, that they are immovable, and cannot be closed or thrown into tension. No valve sound is then heard, a murmur of regurgitation or incompetence taking its place; a murmur of obstruction is also generally heard during the passage of blood in the proper direction through the valve. 2. Feeble action of the heart, as in debilitated states, after continued fever, or during faintness, 86 HEART DISEASE 3. Pericardial effusion, when there is a fair amount of fluid present. 4, Diminution of the blood-pressure. Accentuation of the first sound.—The term azcen- tuation is generally applied to the first sound heard in abnormal conditions, in which, however, the valve curtains are either normal, or not diseased enough to affect their mobility. 1. The tone is clearer, sharper, shorter than normal. Such an accentuated sound is heard with dilated ven- tricles, in which there is a more sudden stretching of the valve curtains owing to the weak, inelastic condition of the papillary muscles. It is also heard when the blood-pressure is increased. 2. The dull, prolonged, and thudding note of ven- tricular hypertrophy is much mufiled in its conduction to the surface by the thickened ventricular wall. 3. When the thickened, almost cartilaginous valves of a.-v. stenosis come together, they produce an abrupt and accentuated sound: which is characteristic of this form of valvular disease. 4. When a heart is lying in contact with a stomach distended with air or gas, the sounds may have a peculiar “tympanitic” ring, which disappears when the flatulent distension passes off. Reduplication of the first sound.—Normally the ventricles contract synchronously, and give rise syn- chronously to the sounds which blend into what we hear as the single first sound. We often hear, however, the single first sound replaced by two sounds—that is, by reduplication or doubling. An excellent imitation of the single or double first sound can be made by striking on the forehead by two fingers synchronously, and then FIRST SOUND 37 with varying interval between the contact of the two fingers with the forehead. The distinctness of the double first sound may vary from a slight degree which has been imitated by the sound frwp to one in which the two component sounds are quite separate (¢er-up). ‘These variations can be well imitated with the fingers on the forehead. The explanation of a double first sound which is usually given is want of synchronism of ventricular contraction generally due to abnormalities of blood- pressure in the two circulations. If one ventricle has more work to do than in the normal condition of affairs, it is said that it will reach that part of its systolic phase at which the first sound is produced earlier than does the other ventricle, and so produce the double first sound. This explanation of reduplication of the first sound of the heart is not without objection. To begin with, the blood-pressure in the left ventricle and the aortic circulation is two or three times as great as that in the right ventricle and pulmonary circulation ; but, on the other hand, the wall of the left ventricle is correspondingly thicker, and there- fore more powerful than that of the right ventricle. If the blood-pressuré in one of the circulations is increasel, one of two things results : 1. More muscle is developed — compensatory hypertrophy—to deal with this increased pressure, and therefore this ventricle is enabled to start on level terms with the contraction of the other ven- tricle ; or— 2. Dilatation of the ventricle and muscle in- capacity results, with dilatation of the valve and consequent regurgitation. ‘This safety-valve action 38 HEART DISEASE relieves the increased pressure on the overworked muscle, and again takes away any handicap as between the ventricles. Physiology teaches us that normally the left side of the heart commences its contraction about one- fiftieth of a second before the right, but this difference is imperceptible to the human ear. It seems to me that we may have another explana- tion of the double first sound when it occurs with actual or relative weakness of the papillary muscles of one or both ventricles. The intraventricular blood-pressure is at its highest after the contraction of the papillary muscles, which occurs at the earliest phase of v.s.; but whilst the papillary muscles maintain their systolic contraction as long as that of the ventricle persists, in the normal condition of affairs, it seems quite possible in disease of the ventricle muscle, or in abnormal pressure in the ventricles—such as is met with in an increased arterial tension—for the papillary muscles to fail after their initial contraction, but before the systole of the ventricle is completed, and allow the valves to fly back and to be put suddenly into a state of secondary tension hy the stretching of the musculi papillares and the chord tendinew. At any rate, it is in conditions which cause increased arterial pressure, and in muscle failure of the ventricle with or without abnormal blood-tension that we get the double first sound. Clinical significance of double first sounds.— 1. Bunetional causes—Doubling of the first sound may not have any pathological significance—that is, it may be heard with no orgame lesion, It may occur at