Effects of Mitral Disease 177 



left axillary line : when the right ventricle is enlarged the impulse 

 extends to the right of the sternum. Displacement of the apex-beat 

 downwards and outwards at once suggests hypertrophy of the left 

 ventricle ; but an extensive impulse within the normal site does not 

 necessarily imply enlargement, it may be due to recession of the lung 

 as in phthisis. 



The extent of the hypertrophy cannot always be made out by 

 percussion, as the heart, instead of pushing the lung aside, may hide 

 beneath it. 



Though the hypertrophied left ventricle labours and hurries to 

 force the blood onwards, it never gets complete mastery over the situa- 

 tion. The result is that when any extra demand is made it becomes 

 embarrassed, and the pulmonary veins, and the vessels of the lungs 

 generally, are over-filled, and aeration is retarded. Thus, shortness of 

 breath is a prominent sign of hypertrophy. 



When the mitral valve is narrowed, also when it is incompetent, the 

 left ventricle has but a small quantity of blood to force into the aorta ; 

 thus, in mitral disease the left ventricle is the only part of the heart 

 which is not hypertrophied. 



In valvular disease of the heart the prejudicial effects pass always 

 in the direction opposite to that of the normal blood-stream. 



The auricles are dilated and their walls thickened when their labour 

 is increased by a narrowing of the gateway into the ventricle, or when, 

 from incompetence of that valve, the ventricle is able to pump some 

 of its blood the wrong way. In mitral regurgitation the left auricle 

 first enlarges, then the right auricle, on account of the obstruction in 

 the lungs, and then the right ventricle. 



The dilatation of the left auricle may cause so much pressure upon 

 the left bronchus (which is close behind it, p. 194) as to obstruct the 

 flow of air through it. 



With mitral insufficiency the hypertrophied and embarrassed heart 

 beats with such vigour against the chest-wall that recognition of the 

 exact murmur may be difficult. A thin layer of lung, however, acts 

 as a cushion and does away with the local excitement, and thus it is 

 that in these cases the murmur is often most distinct towards the 

 axilla. Sibson used to demonstrate this effect of the layer of lung on 

 the heart-sound by placing a piece of blotting-paper between the chest 

 and the stethoscope, and so diminishing the impulse-noise and bringing 

 out the murmur. ' A mitral murmur is a proof of mitral regurgitation, 

 but not of disease of the mitral valve ; it having been noticed in cases 

 in which post mortem examination revealed a healthy mitral valve.' 



The effects of mitral disease. Catarrhal bronchitis, and, later 

 on, cedema of the lung, haemoptysis, and pulmonary apoplexy, may 

 be caused by valvular disease of the heart, the pulmonary veins, and 

 the bronchial veins which open into them, being engorged, and the 

 lung ' splenified.' This condition occurs both when the mitral valve is 



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