Hypertrophy Of The Muscular Substance Of The Heart (hypertrophia cordis) constitutes either total or partial hypertrophy, as it affects the whole, or only some portions of the heart, and is characterized by various degrees of intensity.

Total hypertrophy is, in most cases, so far unequal that it usually preponderates in one section of the heart, - commonly, although not invariably, in the left portion, - where it forms the starting-point of a morbid development of bulk.

Partial hypertrophy affects either the whole of one of the larger sections of the heart, as for instance the walls of one of the cavities, or it attacks only certain parts of that section. Thus it is very frequently limited to the true muscular wall of one ventricle, thickening it in various degrees, while the papillary muscles and the trabecule retain their normal volume, or even where they have become perceptibly thinner and fainter simultaneously with the dilatation of the affected cavity. In other cases hypertrophy principally attacks the papillary muscles and the trabeculae, whilst the true fleshy wall is only moderately increased in thickness. The former of these conditions occurs generally in the left; and the latter, that is to say, an excessive development of the trabeculae, in the right ventricle.

Hypertrophy of the muscular wall of a ventricle may present great variations; it may, in one case, affect the whole, in another it may be limited to one portion of the ventricle, as, for instance the base, the middle part or the septum, or again it may predominate in one or other of those sections.

Hypertrophy of the auricles is generally uniformly diffused over the wall, but it occasionally preponderates in the atrium towards the appendage.

The degrees of hypertrophy present still more numerous differences.

If we follow Bizot's data we must assume that ventricular hypertrophy is present when the thickness of the muscular wall of the left ventricle in men is about 6'" (Paris measure), and in women is about 5'", and when the right ventricle in men is about 3'" in thickness, and that in women 2½'" in thickness. From this point hypertrophy may pass through every varying degree, till it induces so enormous an increase of bulk, that the walls of the left ventricle attain a thickness, varying from an inch to an inch and a half; that the walls of the right ventricle vary from 6 to 9 lines, that the walls of the left auricle vary from 2 to 3 lines, or even more, and that the walls of the right auricle vary from 1½ to 2 lines.

The weight of an hypertrophied heart may range from one to two pounds, and even higher.

The most important and serviceable classification of hypertrophies of the heart is that which is based on a reference to the condition of the cavities of the heart, more especially in regard to their capacity (Bertin, Bouillaud).

1. The capacity of the hypertrophied portion of the heart may remain normal, constituting simple hypertrophy, in which the dimensions of the heart are increased.

2. The cavity of the heart may be dilated, constituting eccentric hypertrophy [hypertrophia excentrica, centrifuga); here also the dimensions of the heart are increased.

3. The cavity of the heart may be contracted, constituting concentric hypertrophy (hypertrophia concentrica, centripeta). The dimensions of the heart may here be increased, normal or diminished.

We shall treat more fully of these different forms when we take into consideration the most essential points relating to dilatation of the cavities of the heart.