When the blood becomes dammed back into the lungs, there is an extra strain upon the pulmonary semi-lunar valves, and then the second sound will be accentuated over these valves on account of the sharp shock which they sustain during diastole. With this accentuation of the second sound over the pulmonary orifice, the first pulmonic sound may be feeble or absent. A subdued or absent first sound shows tension of the artery.
Reduplication of the second sound in a mitral endocarditis is probably due to the difference in time occupied by the ventricles in emptying themselves. A tricuspid murmur occurs in 50 per cent. of the cases of acute mitral endocarditis—a pulmonic in about one-third of the cases. They are superficial and scratchy in character, and indicate a relaxed condition of the vessels and a thin condition of the blood. These murmurs are never permanent. Mitral endocarditis is accompanied by aortic murmurs in about 16 per cent. of cases. Acute mitral endocarditis occurring with chorea is as apt to become interstitial as when it is of rheumatic origin.
Aortic murmurs are usually soft and blowing, but they may be musical, whistling, or twangy. In aortic endocarditis the second sound is usually lost over the carotids. Incompetency of the aortic valves is met with only in the interstitial form of endocarditis.
In about 12 per cent. of the cases of exudative endocarditis arising from rheumatism a regurgitant murmur will be heard at the tricuspid orifice, but such murmurs are not the result of endocarditis of the right heart.
Tricuspid murmurs are present in 50 per cent. of all cases of recent mitral murmurs, in about 40 per cent. of recent aortic murmurs, and in about one-fourth of mitro-aortic murmurs. Such tricuspid murmurs are due to an increase in the slight normal insufficiency existing at the tricuspid orifice. They are of short duration, and are heard over the body of the heart over the right ventricle. Sometimes they are vibrating in character.
In children aortic endocarditis is rare; at this period obstruction at and regurgitation through the mitral orifice commonly occur together.
The physical signs of interstitial endocarditis are such as are due to those changes in the valves which will be considered under the head of Cardiac Murmurs, and their Relations to Valvular Diseases.
DIFFERENTIAL DIAGNOSIS.—Acute exudative endocarditis may be mistaken for pericarditis, and its murmur may be mistaken for the murmur produced by aortitis and for those that develop during the course of fevers.
The friction sounds of pericarditis are superficial in character, and are limited to the præcordial space, while the murmurs of endocarditis are distant, and each murmur will have its area of diffusion beyond the præcordial space. A pericardial sound is distinctly a friction, creaking, or rubbing sound; it has a to-and-fro character, while the murmur of endocarditis is soft and blowing.
Endocardial murmurs accompany the heart-sounds, while pericardial friction sounds are not always rhythmical with the heart-sounds.