The really crucial question which should always be asked is, Is the heart enlarged or decreased in size? The position of the apex beat alone can not determine this, neither can the limit to the right of the sternum. The distance between these two points and the depth of the dullness at a distance of 5 cm. from the midsternal line on the left side, will give the size of the heart as nearly as can be obtained in the living subject. A series of measurements in normal adults average 13 to 14 cm. and 9 to 10 cm. respectively. For women they are about 1 cm. less in each direction.
The elaborate mechanism known as the orthodiagraph is probably the best means of determining the actual limits of the heart, but few men have such an expensive instrument, and, moreover, at the bedside such an instrument could not be used. From comparative measurements I concur in the belief of those who affirm that careful percussion will furnish equally as accurate limits.
The first step in making an examination of the heart is to expose the patient's chest in a good light, and, sitting at his right side, carefully inspect the chest. The position of the apex beat, heaving, bulging, retraction of interspaces, etc., can easily be seen if visible. After careful inspection has given all the data which it is possible to obtain, one next lays the palm of the hand over the heart and attempts to palpate the apex beat. The thrust of the apex in a hypertrophied heart can readily be felt, and one can feel whether the heart is regular, irregular, intermittent, or has other change in rhythm. The shock of the closing valves, particularly the aortic, can be felt, and that and the forcible apical impulse are very suggestive signs of hypertrophy and hypertension. Thrills may also be felt and can be timed in relation to the heart cycle.
It is to percussion that we next proceed, and for the data in regard to the size of the heart, it is, for our purpose, the most valuable of all the physical methods of heart examination.
First and foremost we wish by percussion to learn the actual size of the heart, in other words what is ordinarily called the relative cardiac dullness. With the absolute dullness we are not concerned. That irregular area represents, as has been said, actually the =limits of lung resonance=. The heart may or may not be covered with lung; there may or may not be the incisura cardiaca. What I wish to insist upon is that the size of the area of absolute dullness can give us no data in regard to the size of the heart. What we must endeavor to learn is the actual size of the heart as nearly as our crude means will permit.