EVIDENCE OF ALTERATION IN SIZE - deviations from the normal conditions which afford the most certain indications of changes in the dimensions of the heart., and ought therefore to be especially studied by the learner, are the following : When the heart beats lower down than in health; when the usual shock of its impinging on the parietes becomes diffuse, heaving, undulatory, or irregular; when the dulness on percussion is extended in an inward or an upward direction ; and when the stethoscope reveals sounds which are not heard under ordinary circumstances.
With the exception of the stethoscopic signs, all of these derive their value from their affording the most conclusive evidence which we possess of changes of size in the organ ; and this con sideration ought always to be taken into account in making a diagnosis of disease of the heart. For no important deviation from health can long persist without affecting the muscular struc ture; and alterations in thickness, in capacity, and in power are those which are really efficient in developing the secondary affec tions accompanying the advanced stages of disease.
1. Its impulse being felt at a lower point than usual, is almost a certain sign of enlargement.
2. When the action is heaving and powerful, lifting up the stethoscope, or even the head of the listener, at each impulse, the walls must necessarily be thickened : in such cases the sharpness of the stroke is lost, and its duration prolonged. In other instances the impulse is much more diffuse, and less forcible, the heart coining in contact with different portions of the chest at successive intervals during the prolonged systole, with an undulatory move ment, in which no distinct stroke is felt: we have then reason to believe that the enlargement depends more on increased site of the cavities than on thickening of the walls.
8. Irregularityof action is very important, although of some what indefinite signification. It must not be confounded with intermission when a single beat is occasionally omitted or abortive, or a short pause occurs at certain intervals. Continued irregu
larity must be regarded as a positive sign of disease, but it may coexist with almost any form of lesion. It is probably most fre quently met with in disease of the mitral valve.
4. The extension of dulness towards the sternum derives its value from the eircumstance that there the heart is uncovered by lung, and the liability to inaccuracy is not so great as when an attempt is made to measure it outwards. In enlargement of the heart the percussion dulness is, no doubt, extended in every direction, and a practitioner well versed in the physical aids to diagnosis would be able to detect the exact dimensions of the organ, in spite of interposition of resonant lung-tissue : the student cannot expect to do so with accuracy. In an upward direction diminished resonance may be distinguished with tolerable but when the sound is clear over the sternum it is probably due to some other cause than hypertrophy : it is, for example, especially marked in distension of the pericardial 'sac after pericarditis.
5. In connection with the preceding indications, the stethoscopic signs are most valuable in explaining the causes of increased or irregular action; because the abnormal sounds are produced by actual changes in the relation of solids and fluids, and enable us to assert more or less positively what is the nature of that change.
The altered position of the impulse may possibly be due to an adherent pericardium; but in this case there is very generally also hypertrophy, and the idea of enlargement is probably correct. If it can be shown that there is no enlargement, this alteration of the impulse affords the most reliable evi dence of pericardial adhesion, which after all can only be guessed at.
There ought to be no difficulty in distinguishing the heaving impulse of hypertrophy from the short sharp stroke of nervous palpitation; and yet in very many instances people are told that they have disease of the heart in consequence of the one being mistaken for the other.