PATHOLOGY AND ETIOLOGY.—The neuroses of the heart are functional disorders involving the relations of this organ to the nervous system. The functional disorders of the heart's action affect the frequency, the rhythm, and the force of the cardiac movements. The pathology of these disorders would be more fully understood were our knowledge of the physiology of the heart's movements more complete. We know that contractions of the heart continue when it is separated from all its nervous connections and after removal from the body, especially in cold-blooded animals. The rhythm, frequency, and force of its normal movements are evidently dependent on influences derived through the sympathetic and pneumogastric nerves. Experiments show that the movements continue, but with increased frequency and with irregularity, after division of the pneumogastrics; hence this nerve is regarded as exercising an inhibitory and regulating influence over the action of the heart. Disorders of the heart's action from causes which pertain to the brain doubtless involve especially this nerve. Other causes act through the relations with the different organs of the body by means of the sympathetic system of nerves.
Impoverishment of the blood occasions disorder, probably by affecting the nutrition of the heart. Toxical agents in the blood enter into the pathology in certain cases.
The etiology of functional disorders of the heart's action involves, as an important factor, a predisposition inherent either in the organ or in its nervous connections. A peculiar susceptibility to the causes which induce disorder is an idiosyncrasy. Causes which produce disorder in those who have this idiosyncrasy are inoperative upon others. Some persons are liable to functional disorders of this organ all their lives, whereas some appear to be exempt from any liability thereto. In this respect the cardiac muscular fibres are analogous to those of the pulmonary bronchi. A peculiar susceptibility of the latter is requisite for the capability of having bronchial asthma. The susceptibility of the heart-muscle varies in different persons, and a reasonable supposition is that in proportion to the degree of this susceptibility will the causes of functional disorder be more readily and actively operative.
Clinical observation furnishes evidence of various causes giving rise to functional disorders of the heart. The more prominent are—over-exertion of the faculties of the mind, prolonged mental anxiety, the use of tobacco, tea and coffee taken in excess, too great indulgence in venery, the unnatural abuse of the sexual system, dyspeptic ailments, uricæmia, and anæmia. These causes are often combined in individual cases. With reference to effective treatment, inquiries should be directed in every case to facts relating to these several causes.
Long-continued violent muscular exertions are supposed to lead to functional disorders of the heart. DaCosta has described cases occurring among soldiers during the late Civil War in which the cardiac disorder seemed to him referable to severe marches. He applied the name irritable heart to the condition in these cases.4 It is probable that mental excitement had more or less to do with the causation. Albutt, Seitz, and other observers have attributed functional disorders to over-straining of the heart by occupations which call for severe exercise of the muscles.
4 Medical Memoirs of the United States Sanitary Commission, 1867. See Address before the Philadelphia Medical Society, by A. Stillé, 1883, p. 18. See also Diseases of the Heart among Soldiers, by A. B. R. Myers, London, 1870.
Paroxysmal disorder of the heart belongs among the multifarious symptoms referable to the nervous system in cases of hysteria. It is among the toxical manifestations embraced in the clinical history of gout, being referable, when it occurs in this pathological connection, to uricæmia. It may have this causation in cases in which the ordinary gouty manifestations do not occur.
In the variety of disorder characterized by infrequency of the heart's action it may be assumed that the causative agency is exerted through the pneumogastrics. The inhibitory function of this nerve is affected in the same way as by the galvanic current in the experimental observations on animals in illustration of this function. This view is corroborated by the frequent association of this variety of disorder with notable cerebral disturbance.
PROGNOSIS.—A purely functional disorder of the heart's action may be said to be devoid of danger to life. This is a remarkable fact, taking into view the importance of the organ, together with the degree and the duration of disordered action in some cases. Of many thousand cases which have come under my observation, I am not aware of having met with a single instance in which death was fairly attributable to an uncomplicated functional disorder. It is readily understood that functional disorders superadded to, albeit not dependent upon, organic affections of the heart may contribute to a fatal termination. But the tolerance of functional disorders under these circumstances is often very remarkable.
The assurance of the absence of all danger frequently lifts from the minds of patients a heavy load of anxiety and apprehension. To be able to give such an assurance is one of the delights of medical practice. Patients often find it difficult to believe that the disorder from which they suffer can take place while the heart is organically sound. Many require very positive and repeated assurances in order to secure their belief. The question is many times asked, "How is it possible that I should suffer so much, and yet the heart be free from disease?" Another question which is apt to be asked is, "How can you ascertain so quickly that there is no disease?" In anticipation of the latter question, in order to ensure the desirable moral effect, it is sometimes good policy to prolong the examination, inasmuch as for the exclusion of all the physical signs of organic disease a few moments only are required. Another question, still, is, "Will not organic disease be likely to be produced by the functional disorders?" The physician is fully warranted in giving a negative answer. Exclusive of the cases of exophthalmic goitre, functional disorders of the heart do not involve liability to either inflammatory or structural affections.