MITEAL STENOSIS. 257 



heart. Its outline, as projected on the surface, has already been 

 defined. Its inferior wall rests on the diaphragm. The results 

 of hypertrophy of this chamber are the appearance of pulsation 

 in the epigastrium and an increase of cardiac dulness in two 

 directions, namely transversely to the left and upwards on the 

 left side of the sternum. The upward extension of dulness is 

 due to an increase in size of the conus arteriosus, which is that 

 part of the right ventricle from which the pulmonary artery 

 springs. The appendix of the left auricle normally lies in the 

 position occupied by the upward extension of dulness, but as a 

 rule the enlarging conus completely displaces the auricle. The 

 enlarging right ventricle, pushing its way to the left, ultimately 

 may completely separate the left ventricle from the anterior wall 

 of the chest, and also takes the place of the latter cavity in 

 producing the cardiac impulse. As a result the impulse is 

 displaced mainly to the left and not so much downwards as in 

 hypertrophy of the left ventricle. 



The increasing pressure in the pulmonary circuit ultimately 

 affects the right auricle. The outer limit of this auricle normally 

 extends an inch and a half to the right of the sternum. It is 

 covered by the anterior part of the right lung, and consequently 

 takes no part in the superficial cardiac dulness. The presence of 

 a wedge of lung tissue in front of the auricle, and the close 

 approximation of the costal cartilages in this situation are 

 obstacles to the satisfactory examination of this cavity of the 

 heart. Increase in the size of the cavity causes the superficial 

 cardiac dulness to extend up to or beyond the right margin of 

 the sternum. Only when the auricle is much distended and the 

 lung retracted is actual dulness obtained to the right beyond the 

 sternal edge. Earely the auricle may be seen to pulsate in this 

 situation. 



From what has been stated it will be gathered that the area of 

 cardiac dulness is increased in three directions by mitral stenosis. 

 The main increase is transverse to right and left, but there is also 

 an extension upwards, consequently the percussion outline of 

 pericardial effusion is in some instances very closely simulated. 



C.A.A. 17 



