The part of the heart which most suffers in rheumatic fever is the fibrous structure of the rings and valves. We have seen that inflam mation of the endocardial lining is always secondary to a prior in flammation of the fibrous structure of a valve; and that there is good reason to believe that in many cases of pericarditis the inflamma tion spreads to that membrane from the fibrous structures at the base of the heart. If inflammation spreads from these structures to the endocardium and the pericardium there is no reason why its hould not equally extend to the muscular substance. There is every facility for its doing so, for the muscles of the heart are attached to the fibrous rings, and there can be little doubt that many cases of par tial myocarditis in which the inflammation is limited to the base of the heart are so produced.
Rheumatic myocarditis, like rheumatic endocarditis, is almost entirely confined to the left ventricle, and for the same reason. It may be partial or general--involving a part, or implicating the whole structure of the muscular wall. The partial is the more common. Its situation is the base of the ventricle. It is probably due in most if not in all cases to an extension to the muscles of a prior inflamma tion of the fibrous structures. As there is usually a similar extension of that process to the endocardial lining, any symptoms to which the myocarditis might give rise are apt to be lost in the more obvious in dications of the endocarditis. The evidence of its occurrence is found in the post-mortem room in the form of circumscribed patches of in duration of the muscular walls of the ventricle, chiefly at the base and generally in company with thickening and induration of the fibrous rings and valves.
General rheumatic inflammation of the walls of the left ventricle, like other local inflammations, occurs in varying degrees of severity. When very acute, it may give rise to such destructive change in the ventricular walls that recovery is impossible. In a less severe form it causes simply softening of the ventricular walls—a condition which may he perfectly recovered from, or may result in more or less indu ration of the muscular substance; but which may also be a cause of sudden death.
Myocarditis is a formidable disease, apt to be fatal, and apt to be overlooked. It is apt to be fatal, because of the importance of the tissue inflamed; it is apt to be overlooked, because of the obscure and even misleading character of some of its most common and promi nent symptoms.
Corvisart divided cases of myocarditis into two classes, the dis tinct and the latent—those in which the symptoms clearly indicate the nature of the disease and those in which symptoms directly referable to the heart scarcely exist.
Acute pain in the epigastrium, or prmcordial anguish, a sense of oppression and anxiety, embarrassed respiration, the evidence of defective aeration of the blood, without any pulmonary lesion to ac count for it—such are the symptoms which may present themselves in distinct cases of acute myocarditis. Seldom, if ever, do they all exist at the same time. Now one, now another predominates. The most common are pmcordial uneasiness, and evidence of defective aeration of the blood. With these there are associated symptoms of disturbance of the sensorium.
Myocarditis is often accompanied by inflammation of the endo cardium or pericardium, or both. It is then part of a general car ditis. The physical signs of the membranous inflammation are so obvious, that all the symptoms are apt to be ascribed to it. It is probable that the less obvious myocarditis plays a not unimpor tant part in the production of many of them : but how much of the patient's disturbance is due to the membranous and how much to the muscular inflammation it is impossible to say. It is a matter of course that when both the walls of the ventricle and the membranes are inflamed, there is likely to be greater distur bance and irregularity of the heart's action and a greater tendency to death, than when the membranes only are involved. But it is impossible to diagnose the extent of the myocarditis as we do that of .the endo-pericarditis. All that we can say is that, if in the course of a case of rheumatic inflammation of the membranes, we find either a marked degree of cerebral disturbance without hyper pyrexia, or evidence of defective blood purification without any pulmonary lesion, or any serious amount of pericardial effusion, we may feel sure that the muscular substance of the heart is seriously involved in the mischief.
The physical signs of the membranous inflammation so predom inate over any change in the cardiac sounds to which the myocarditis could give rise, that we can better diagnose the existence and gauge the extent of this latter by a careful observation of the general symp toms, than by a physical examination of the heart.
There are cases of acute myocarclitis, as of acute pericarditis, which run their whole course to a fatal termination without any symptom directly referable to the heart; the only symptoms being those of cerebral disturbance. An admirable illustration of this is found in a case recorded by Mr. Stanley in the seventh volume of the Medico-Chirurgical Transactions, 1816. So far as I know, it is the earliest recorded case of the kind.