ESSAY III.
Morbid Anatomy of the Muscular Substance of the Heart.
Dr. Baillie, speaking of inflammation of the substance of the heart, says, "When the pericardium covering its surface is inflamed, the inflammation sometimes passes a little way into the substance of the heart:" and then he gives these as the characteristic marks of such inflammation—that "it (the substance of the heart) becomes much more crowded with small vessels than in its natural state, and there are sometimes to be seen a few spots of extravasated blood." Now, this undue vascularity, and these few extravasated spots, where inflammation unquestionably belongs to a contiguous structure, may be deemed sufficient evidence of the muscular substance of the heart participating, or beginning to participate, in the same disease; but, absolutely and exclusively, it may be doubted whether more is not required to give a certain assurance of its inflammation. Here, as elsewhere, we must look for some of the proper products of inflammation; or for some of the permanent changes of texture which naturally result from it, according to its several modes of disorganizing.
It is a very rare event to find pus among the products of inflammation of the substance of the heart: yet this event has occurred twice to my observation. In one instance the whole heart was deeply tinged with dark-coloured blood, and its substance softened; and here and there, upon the section of both ventricles, innumerable small points of pus oozed from among the muscular fibres. This was the result of a most rapid and acute inflammation, in which death took place after an illness of only two days. In another instance, after death, which terminated an illness of long duration and characterized by symptoms referable to the heart, a distinct abscess was found in the substance of the left ventricle, closed externally by a portion of adherent pericardium, and connected internally with an ossified portion of the lining membrane.
This diffusion of pus, or rather its formation in innumerable separate points, throughout the muscular structure of the heart, by a rapid and acute inflammation, is a singular occurrence. No such case has ever fallen within the knowledge of the most experienced in morbid anatomy, of whom I have made inquiry; neither has any such (as far as I can learn) been recorded in books[10].
A single collection of pus[11], constituting an ulcer or abscess of the heart, and resulting from chronic inflammation, is also a rare occurrence, yet not so rare but that a specimen of it may be found in most collections of morbid anatomy[12].
But independent of the formation of pus, softening and attenuation, as well as induration and thickening of the muscular substance of the heart, do, in different cases, according to the circumstances under which they are found, both bespeak inflammation.
Together with the unequivocal evidence of inflammation in other parts of the heart, the muscular fibres have at the same time been found very soft and loose, and easily torn; and with this looseness of texture the heart has sometimes presented a dark and almost black appearance, and sometimes it has been almost blanched and colourless. The deep dark tinge shews that the muscular substance is unnaturally loaded with blood; whereas the absence of colour shews that it is destitute of its natural quantity. These different appearances do, in fact, belong to different stages of the same disease. The first indicates inflammation of the muscular substance in its present state of activity; the second, an irreparable disorganization of the muscular substance left by inflammation, when it has been unarrested in its earliest stages. The first is found when death takes place in a few days after the accession of the disease; the second, when the patient survives the first attack, and dies at a remoter period.
The inflammation, which produces softening and attenuation of the muscular structure, is, I believe, always of an acute kind.
But induration and thickening of the muscular substance of the heart is also the result of inflammation. This must be distinguished from hypertrophy, or mere augmentation of bulk, of which we shall speak hereafter. In this induration, which proceeds from inflammation, there is, besides increase of bulk and firmness, a manifest alteration of texture. A substance[13] is produced offering a peculiar resistance to the knife. This condition unquestionably must result from an interstitial deposition of new matter among the muscular fibres. From concomitant circumstances, as well as from its own character, I presume that it proceeds from chronic, not from acute inflammation. I confess that I never saw a specimen of what I now allude to. It is described with some minuteness by Corvisart; but it may be presumed to be very rare, since Laënnec admits that it never fell under his observation.
These opposite states of softening and attenuation in one case, and induration and thickening in another, are known to those conversant with morbid dissection as the evidences of inflammation in other parts of the body besides the muscular substance of the heart.
But there are changes of structure incident to the muscular substance of the heart which are independent upon inflammation, or, perhaps, upon any process which can properly be called morbid. They consist of simple augmentation and simple diminution of bulk and consistence. This simple augmentation of bulk and consistence is owing exclusively to a more ample development of natural structure. The muscular substance is more red than natural, its carneæ columnæ are increased in thickness, and its proper fibrous texture is every where more strikingly manifest; but there is no interstitial deposition of matter new in its kind. It has been called hypertrophia of the heart, and the name conveys a tolerably just idea of its actual condition.
The simple diminution of bulk and consistence is a condition the exact opposite of the former. The muscular substance is less red than natural; its proper fibrous texture less distinguishable; but there is still the appearance of muscle shrunk and withered, as if from an insufficient supply of nourishment. It may be called atrophia of the heart.
Conjoined with augmentation, as well as with diminution of strength and bulk in the walls of the heart, there is almost always an increase in the capacity of its cavities; and in whichsoever part of the heart the walls are thus augmented or diminished, it is the cavity appertaining to the same part which undergoes the increase of capacity. Hence it appears either that one of these conditions is the immediate and necessary consequence of the other, or that both are the simultaneous effects of the same causes.
Dilatation of any cavity of the heart, with thickening of its walls, is called active dilatation; and dilatation of any cavity, with attenuation, is called passive[14].
Active dilatation may appertain to every cavity of the heart simultaneously; and so may passive dilatation. But such occurrences are very rare: for one cavity being naturally more liable to this species of dilatation, and another to that, it most frequently happens that specimens of both conditions are found in the different cavities of the same heart.
The left ventricle is much more liable to active dilatation than the right; and the right ventricle more so than either of the auricles; and of the auricles unquestionably the left. Upon the whole, perhaps, the fact may be truly stated thus—that the left ventricle commonly gains an increase of bulk and strength, with an increase of capacity; and that all the other cavities, at the time that they expand, are rather apt to become attenuated.
It sometimes (though rarely) happens, that, with an increase of strength and bulk in its muscular structure, the left ventricle suffers a diminution of capacity in its cavity. In a case reported by Laënnec, the left ventricle was an inch and a half thick at its broadest, and an inch thick at its thinnest part; and yet its cavity was only capable of containing an unblanched almond. I have seen the same condition in a less degree.—(Laënnec, vol. ii. 698.)
The circumstances under which these opposite conditions, this hypertrophy and atrophy of the heart, with the enlargement or diminution of its cavities, arise, must be explained hereafter. At present I would only remark that they are often found conjoined with actual disease in other structures of the heart, such as osseous or cartilaginous thickening of internal lining, adhesion of the pericardium, and ossification of the coronary arteries, to which they owe their origin; and, moreover, that they are often found where the heart is otherwise perfectly sound in texture, and where their cause must be sought in other parts of the body.
The heart is liable to undergo a simple dilatation of its cavities without either thickening or attenuation of its muscular substance. This simple dilatation is sometimes of the whole organ, sometimes of one side, and sometimes only of one auricle or ventricle. When it is of one cavity only, it may be complicated with active or passive dilatation of another, or of all the rest.
There is reason to believe that the heart sometimes undergoes a temporary dilatation, and again returns to its natural capacity; but that the dilatation can only subsist for a short time without becoming permanent.
The power of thus enlarging its cavities, and restoring them to their natural condition, belongs more especially to the right side of the heart.
A large accumulation of fat is sometimes met with about the heart.
The healthy heart is always more or less marked upon its external surface with streaks of white, and this appearance results from the deposition of fat in the cellular texture, which unites the serous covering with the subjacent muscular structure. It is found principally where the venæ cavæ unite to form the right auricle; also at the base of the ventricles, and along the line which marks the boundary between the two, and around the origin of the great blood-vessels as they emerge from the heart. But when fat is deposited in more than these situations, and in more than the natural quantity, it is not so much added to the healthy substance of the heart, as existing at its expense and detriment, and the muscular structure is that which especially suffers. The fibre of the fat heart is pale and wasted, like that of a paralytic limb.—Mus. of the Coll. of Surg. 327.
A rupture of the heart is sometimes met with; but all the cases of reputed rupture are not such in reality. An aperture in the walls of the heart, through which blood escapes into the cavity of the pericardium, may result from ulceration as well as from rupture, or from a mixed process of one and the other; but whatever be the precise nature of the process by which this perforation of the heart is effected, it is undoubtedly of rare occurrence.
Where it has been found, there has generally been at the same time some peculiar condition of the organ, which might be presumed favourable to its production. Its muscular substance has been so soft and loose of texture, that it could be pierced through by the weight of a probe[15]; or it has been converted into, or greatly intermixed with fat[16]; or its muscular fibres have been absolutely defective, leaving a certain transparent space, where the internal lining and the pericardium have been in contact, and served to maintain the completeness of the cavity, until the rupture has taken place[17].
Not that a rupture has not been found where the texture of the parts has seemed to offer no natural facilities to its occurrence—as in the case related by Harvey himself, who found a lacerated aperture in the left ventricle, capable of admitting his finger, through which blood had escaped into the pericardium, the walls of the ventricle being increased in thickness and strength, while an obstacle existed at the entrance of the aorta[18]. Here the heart must have torn itself asunder by the simple violence of its contraction, in contending against the impediment to the egress of blood from its cavity. This is an effect which would hardly be thought capable of being thus produced; but I can well believe it possible after having seen one of the recti muscles of the abdomen literally torn in twain, in a man who died of tetanus[19].
[To be continued.]