§ 5. 'Valvular Lesion.—This form of disease is that which is essentially associated with endocardial murmur ; but as, in speak ing of the murmur, it has been shown how it may be produced without alteration of the structure of the valves, so here it is to be remembered that valvular lesion may be found after death, which has not been discovered by the presenee of a bruit during life. Our inquiry must, therefore, not be limited to the use of action sh spe ; we must ascertain the previous existence of examin nm, or the coincidence of ailments with which we know life w of the heart is more or less constantly associated: g these one of the most frequent is dropsy, and, as a general e, it may be said that, when not produced by albuminuria, it is seldom found with any disease of the heart of which valvular imperfection is not a prominent feature. Probably, in the first instance, valvular lesion always gives rise to bruit : it is when the circulation becomes laborious and irregular that the murmur is lost or indistinct, and then the evidence of disease is s9 clear that it is quite unnecessary as a confirmation, and its value only con sists in its giving an explanation of the circumstances which have led to the advanced changes of which other indications have ren dered us cognizant.
In diagnosis we have, therefore, to do with the fact of imperfect closure of the valves under two aspects. In its first appearance, prior to other changes, when we may be called upon to determine how it is likely to affect the duration of life or the enjoyment of health, when the presenee of the bruit is the only evidence of disease; and, at a later period, when very considerable alteration of mus cular structure has taken place, and the imperfection of the valve though in truth the cause of these changes, may or may not be revealed by any actual murmur ; in the latter, as in the former, there are many important questions with reference to the prog nosis and treatment, with which diagnosis has not anything fur ther to do than in establishing the fact.
With reference to the first class of cases, the student has to remember the three forms of endocardial murmur which we fouCd to afford the most trustworthy evidence of disease ; (1) a diastolic bruit ; (2) a systolic bruit at the apex, of very local character • (8) a systolic bruit at the base, heard loudest below the third rib: and relatively louder towards the right side of the sternum, than towards the left shoulder. With reference to the second class, the existence of a bruit is a pretty certain indication of valvular im perfection; but this may be due not so much to change in the structure of the valve, as to enlargement of the cavities of the heart, which has altered the relation naturally existing between the size and position of the aperture, and that of the valve which is designed to close it. When no bruit is present, we must be guided by the general symptoms of the case; venous congestion and a weak pulse, while the heart is acting powerfully, must, for example, be taken as conclusive proof of valvular lesion, whether we hear a bruit or not.
At the risk of some repetition, let us for a moment consider the progress of the blood through the central organ. It passes onward through the mitral valve during the diastole, beginning its movement directly after the shock of the apex against the rib ; it is performed slowly and silently, with but little force; and for a diastolic bruit to be produced, there must be very considera ble roughness or change in the form of the orifice, to throw the blood into vibration. An anemic condition is never sufficient to develop sonorous
vibrations with a healthy mitral valve. As soon as the systole begins, the valve-flaps ought to come together, to prevent any blood from escaping in that direction ; and a systolic bruit can only be produced by their imperfect closure : but as the force with which the ventricle contracts is considerable, a very slight defect is sufficient to produce this regurgitation, which, se it en counters the opposing current, very easily produces a bruit. It is not the rough ness that occasions the murmur in this case, because it is just as distinct when the valves cannot close perfectly from any other cause, such as dilatation of the heart, when the flaps are too small for the aperture, shortening or rupture of any of the chordie tendineie, &c. Its position is remarkably local, most com monly between the same ribs where the apex-beat is felt, and somewhat nearer the sternum ; sometimes in the interspace above : and, though localized to a certain extent, by tbe sound being more readily heard through the interspace, still it has a distinctnese at one spot which no other endocardial murmur pre sents. From the latter point it is that the diastolic mitral murmur also pro ceeds ; but it can be traced onwards towards the centre of the heart.
Following the course of the blood, we find it passing through the ventricle ; and now commence the vibrations in mimic subjects which are heard in the praicordial space or in the aorta ; next it passes the portal of the aorta, and if the valves be roughened or stiff, even healthy blood is thrown into vibration, and a bruit is developed which has for its point of greatest intensity the third interspace, commencing before the apex impinges against the thorax, and terminating after it : if the blood be at all altered by mem* this bruit crosses the sternum, and can be heard on its right side. As soon as the systole is completed, the aortic valves fall backwards and close in health : in disease the adaptation may still be perfect, and the 2d sound of the heart dis tinct, though a syatolic aortic bruit exist ; but their adaptation may be imper fect, or a perforation may exiiit ; and then the blood, in place of being held back by the valves, repasses into the ventricle, in consequence of the pressure exerted by the resiliency or contractility of the aorta. It may have to pass over stiff and rough valves, and be thrown into vibration as it passes, or it may pass through a smooth opening and no bruit be developed at the valve ; but it very soon encounters the current entering in the opposite direction from the auricle, and vibration must result, and a bruit be formed. A diastolic aortic murmur is therefore always audible at the centre, and even onwards to near the apex of the heart, increasing in distinctness as we descend ; but it may also be traced from the third interspace.