PRACTICAL CONSIDERATIONS: THE HEART. 711 



tion of blood through an auriculo-ventricular valve that does not accurately close the 

 corresponding opening or (b) to an obstruction to the exit of blood from the ven- 

 tricle at the aortic or at the pulmonary orifice. 



If a heart murmur is not synchronous with the radial pulse (diastolic or pre- 

 systolic), it may be caused by {a) obstruction to the passage of blood from an 

 auricle into a ventricle (mitral or tricuspid stenosis); or \b) regurgitation from the 

 pulmonary artery or aorta into the right or left ventricle (pulmonary or aortic insuf- 

 ficiency). 



Of these various murmurs those due to mitral and aortic insufficiency are by far 



the most frequent. 



Valvular disease of the left side of th^ heart (90 per cent, of all cases) is more 

 frequent on account of the greater work required of this side and the associated 

 greater liability to strain, rarely sudden, usually trifling but oft repeated. 



1. Mitral iyisufficiency — an imperfect closure of the segments of the left auriculo- 

 ventricular valve — causes a systolic murmur, heard best {a) over the apex and super- 

 ficial cardiac area because there the ear can most nearly approach the left ventricle' 

 without the interposition of pulmonary tissue or of the right ventricle ; (<5) in the 

 axilla, because it is transmitted in the direction of the arterial blood-cui-rent ; and (r) 

 at the angle of the left scapula, or between the fifth and eighth thoracic vertebrae, for 

 the same reason, and because at that point the left ventricle is posterior. In addi- 

 tion, the pulmonary second sound is louder and sharper than natural (accentuated) 

 because of the following series of occurrences which should be studied in connection 

 with the structures and cavities involved : over-filling and distention of the left 

 auricle, imperfect emptying of the pulmonary veins, pulmonary congestion and re- 

 sistance to the systole of the right ventricle, increased fulness of the pulmonary arter- 

 ies, and corresponding increase of the backward pressure upon the pulmonary 

 valves, shutting them more sharply and forcibly (accentuation). 



Furthermore, as the distention of both ventricles results in hypertrophy, the 

 transverse diameter of the area of cardiac dulness is distinctly increased. 



2. In 7?iitral stenosis (often associated with some degree of mitral insufficiency) 

 a murmur is usually heard, preceding the pulse-beat (presystolic), — corresponding, 

 that is, to the auricular systole, and, as the left auricle is distended — from imperfect 

 emptying — and hence the pulmonary veins and arteries and the right heart are 

 in the same condition, there is again a loud accentuation of the second sound. 



3. Aortic insiifficioicy is characterized by a murmur that follows the radial 

 pulse (diastolic), occurs a^ the blood is being driven back into the ventricle by the 

 elastic aorta, is heard best over the sternal end of the second right intercostal space 

 {vide supra) , is often propagated towards the xiphoid cartilage or down the left side 

 of the sternum, and is more rarely heard in the carotid or axillary vessels, — i.e., as 

 it is a murmur primarily due to the reflux of blood from the aorta into the ventricle, 

 it is, in accordance with well-known laws of physics, transmitted in the direction of 

 the current causing it. 



The great distention and subsequent hypertrophy of the left ventricle caused by 

 its inability to empty itself result in 9, marked increase of percussion dulness. As 

 the aortic valves do not come together normally, the aortic second sound is feeble or 

 absent. 



4. Aortic stenosis (much less frequent than insufficiency) is usually accompanied 

 by a systolic murmur heard at the aortic cartilage and transmitted along the great 

 vessels to the axilla, to the neck, and along the spine, but difficult to distinguish from 

 similar murmurs caused by disease of the inner coat of the aorta or by mere 

 roughening of the valves. As the aorta receives a diminished quantity of blood, 

 one factor in the production of the apex beat is lessened in effectiveness and the 

 cardiac impulse is often also lessened. Dilatation and hypertrophy of the left ven- 

 tricle with subsequent secondary changes in the other cavities may follow, but are 

 not nearly so marked as in aortic insufficiency. 



Valvular disease of the right side of the heart may, on account of its relative 

 infrequency and to avoid repetition, be even more briefly summarized : 



I. Tricuspid insufficiency — often following pulmonary conditions obstructing the 

 circulation — is characterized by {a) a low systolic murmur heard well over the 



