File:Diseases of the chest and the principles of physical diagnosis (1920) (14778273864).jpg

Identifier: diseasesofchestp1920norr (find matches)
Title: Diseases of the chest and the principles of physical diagnosis
Year: 1920 (1920s)
Authors: Norris, George William, 1875-1965 Landis, Henry R. M. (Henry Robert Murray), 1872-1937, joint author Krumbhaar, E. B. (Edward Bell), 1882-1966
Subjects: Chest Diagnosis Thoracic Diseases Diagnosis
Publisher: Philadelphia, W. B. Saunders company
Contributing Library: Columbia University Libraries
Digitizing Sponsor: Open Knowledge Commons

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osed and contracted. and in those who are the subjects of atheromatous changes in the arteries,especially the aorta. It is rare among women. Occurring as a singlelesion it is not often caused by acute rheumatic fever. Morbid Anatomy.^—The anatomical changes which take place in thesemilunar valves are precisely similar to those which occur in the intimaof the blood-vessels and ending in atheromatous degeneration. As aresult, the leaflets become fused, stiff, and rigid and obstruct the free ENDOCARDITIS 741 escape of the blood from the left ventricle into the aorta (see Fig.404). In some instances the obstruction is made worse by vegetationswhich develop during an attack of secondary endocarditis (see Fig.405). The resistance offered adds to the work of the left ventricle which,as a consequence, becomes hypertrophied. It is in this variety of val-vular lesion that the so-called concentric hypertrophy is most nearlyapproximated. Practically, however, some degree of dilatation is always
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Fig. 405.—Aortic obstruction, seen from above. The leaflets are fused together, thick-ened, and indurated. They are covered with small vegetations. present. When the heart can no longer overcome the obstruction, dila-tation and the phenomena of broken compensation ensue. Pathological Physiology.—The mechanism of aortic stenosis is quitesimple. Owing to the obstruction to the ventricular outflow, theblood-pressure in the left ventricle is increased, sometimes to twicethe normal. Another effect caused by the obstruction is to prolongthe time of emptying the ventricle and as a result the ventricular systole 742 DISEASES OF THE PERICARDIUM, HEART, AND AORTA may consume from 5 to 50 per cent, more than the normal time. Ifthe obstruction becomes too great or the muscle becomes exhausted, aninsufficient amount of blood reaches the systemic circulation and as aresult the pulse pressure becomes small and symptoms of cerebralanemia may develop. In cases of aortic stenosis the left ventricle

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