There are three characteristic points about the enlarged area of dullness: (a) The apex-beat, as determined either by palpation or auscultation, is found to lie an inch or two within the left border of dullness. (b) The cardiac impulse is feeble and difficult of appreciation, which would not be the case if the ex tensive dullness were due either to hyper trophy or dilatation of the heart itself. (c) The normal heart-sounds are feeble and distant, while perhaps the radial pulse is comparatively strong.
A large collection of fluid may affect the pulse in a peculiar way, which, al though not pathognomonic, is of consid erable value. The "paradoxical" pulse, as it is called, varies with the cycle of respiration, becoming weaker or imper ceptible during inspiration.
The distinctive auscultatory sign of pericarditis is the friction-sound. This may be heard over any part of the heart, more frequently, however, at the base than at the apex. It is near the ear, in creased by gentle pressure with the stethoscope, and is described in various cases as rubbing, grating, or creaking; it is apt to be somewhat harsh and it may be interrupted, or "jerking." It may be systolic or diastolic in time, more often it is a double murmur, and it may be triple. In any case it is not apt to be exactly synchronous with the systole and diastole of the heart. In this respect, as well as in its nearness to the ear, it differs from the endocarditic murmurs, and it also differs in the limited area over which it may be heard.
The pericarditic friction is not trans mitted so far as are valvular murmurs. Friction may not be heard when the pa tient is lying horizontally, and become audible when he sits or bends forward. Sometimes it is heard inside the angle of the left scapula. The intensity of the friction is influenced by respiration, be ing usually louder during inspiration.
The heart-sounds proper are feeble and distant, or they may be drowned by the friction-murmur. Cases which present both endocardial and pericardial mur murs are naturally perplexing.
Certain accessory signs in the lung re main to be mentioned. In the case of large effusions the percussion-sound in the left axilla at about the level of the nipples is a muffled tympany; poste riorly below the angle of the left scapula the compressed lung may give a slight dullness on percussion and bronchial breathing.
The rapidity of the process varies greatly. Sometimes a dry pericarditis lasts but few days; a rheumatic pericardi tis may cause a rapid effusion of sero fibrin, so that in forty-eight hours the sac will be much distended; and in other instances there is a gradual increase of fluid for several weeks.
In septic cases pus develops rapidly, and death may ensue in three or four days. Rheumatic cases usually pursue a favorable course, and seldom demand active interference. On the other hand, when the pericarditis complicates pleu risy, pneumonia, valvular disease of the heart, or chronic nephritis, life is in great danger. Tubercular pericarditis is al most absolutely hopeless, although it may pursue a chronic course.
Diagnosis. — From what has already been said it follows that in some instances pericarditis cannot be diagnosticated, subjective and objective symptoms both failing. Other cases are self-evident. In a third class of cases we have the possibil ity of confusion with endocarditis; hy pertrophy, or dilatation of the heart; myocarditis; and localized pleurisy.
The endocarditic murmurs are apt to be localized at places corresponding with the valves of the heart, and to be trans mitted farther than friction-sounds. They are, moreover, synchronous with the heart's movements, and they usually have a softer, blowing, and distant char acter, which contrasts with the harsher sound, near the ear, of pericarditis.
The hypertrophied heart is usually easily distinguished from pericarditis; the impulse is vigorous, the heart-sounds loud, and the outline of dullness is, al though greater than in health, yet ap proximately normal in shape.
Certain cases of dilatation of the heart are perplexing, especially where the peri cardial friction-sound has been heard within a short time previous. The ob server is obliged to consider carefully whether the enlargement of the cardiac area of dullness and the feebleness of the heart-sounds are due to change in the heart-wall or to an effusion outside of it.
In dilatation the heart-sounds are clear, and the first sound of the heart may be, although valvular, quite strik ingly distinct. The apex of the heart is never displaced upward by mere dilata tion.