Synonyms.—Brachycardia; Slow Heart.

Definition.—Bradycardia is slowness of the heart, either normal, physiological (bradycardia), or pathological, which may be symptomatic and due to some other lesion, or it may be due to a neurosis.

Etiology.—There are some cases where the slow heart is seemingly physiological, the patient being apparently free from disease, though the pulse-rate may be only sixty. However, as many cases of organic heart disease are only made post-mortem, it may be a case of mistaken diagnosis.

The most frequent cause is the toxemia caused by the infectious fevers, especially typhoid fever, pneumonia, diphtheria, erysipelas, influenza, and acute rheumatism. Riegal, who analyzed 1,047 cases of bradycardia, where the pulse was less than sixty, found more cases from the acute fevers than from any other cause. Baumgartner cites a case where the pulse was only twenty-five, in the latter stage of diphtheria.

Next in frequency, according to Riegal, are wrongs of the digestive tract, 397 cases having, as a cause, some wrong of the gastro-intestinal tract. Chronic dyspepsia, either due to functional wrongs or from ulceration or cancer of the stomach, gives rise to more or less general enfeeblement, attended by a slow pulse. Wrongs of the liver act in the same way.

Bradycardia not infrequently follows confinement, owing, no doubt, to the severe exertion and the loss of so large an amount of fluid during delivery, causing exhaustion.

A slow pulse is found in diseases of the coronary arteries, sclerosis, stenosis of the aorta, and in degenerations of the myocardium.

Wrongs of the urinary apparatus may also be followed by bradycardia. Thus, in one case of nephritis with bladder complications, I rarely found the patient's pulse as high as sixty, it usually running about fifty.

Although tea, coffee, and alcohol usually give rise to tachycardia, they may also be responsible for bradycardia.

Chlorosis, anemia, diabetes, and kindred lesions, are sometimes the causes of slowing of the pulse.

Lesions of the nervous system are sometimes accompanied by slowing of the pulse; thus apoplexy, meningitis, tumors of the cerebrum and medulla, and injuries to the cord, give rise to bradycardia.

Bradycardia is sometimes associated with a neurosis, as seen in epilepsy, hysteria, mania, and paresis.

Pathology.—There are no changes characteristic of bradycardia, and when purely a neurosis, tissue changes are absent; and where structural change is found, it is rather a coincident than a result.

Symptoms.—The slow heart-beat, which is the characteristic symptom, may be temporary or permanent, and, when temporary, usually comes on suddenly and terminates in the same way, though a gradual return to the normal heart-beat is not uncommon. During an attack there may be twitching of the muscles, especially where it is epileptiform in character.

An attack may come on unannounced, or be preceded by ringing in the ears, dizziness, and a sense of impending danger. There may be great prostration, which is quite pronounced when myocardial degenerations have taken place.

The pulse-rate varies, and may be from fifty, to as low as eight or ten per minute, and is weak and small.

When the heart is very feeble, the impulse may not be felt regularly at the wrist, and sometimes the radial pulse intermits every other beat, the pulse at the wrist numbering but half the number of the regular heart-beats; for this reason auscultation should always be performed while taking the pulse-rate in bradycardia.

During an attack, the patient may have repeated attacks of syncope, or he may lose consciousness early in an attack, and remain so for hours, consciousness being followed by prostration and a sense of weariness.

Diagnosis.—The diagnosis is readily made by comparing the pulse-rate at the wrist with the heart-beat, which is determined by auscultation; they should be synchronous, and less than fifty in number per minute.

Prognosis.—The prognosis depends altogether upon the cause; thus, if the result of myocardial or cerebral degenerations, the case is hopeless, death usually occurring suddenly.

Treatment.—The treatment consists of two parts: First, to overcome the paroxysm; and, secondly, to prevent its return. For the first condition we usually resort to stimulants; ammoniated tincture of valerian, from thirty to sixty drops in a little sweetened water, is often beneficial. Strychnia, from the sixtieth to the thirtieth of a grain hypodermically, will also give prompt relief.

During the interval between attacks a careful study of the patient's condition should be made, and our treatment be directed to overcoming the exciting causes.

When there are no structural changes, such as degenerations of the heart and brain, the patient may be assured that his life is in but little danger. When the slow heart is due to reflex conditions, a careful search should be instituted, and the cause removed. In one case it may be due to sexual excesses; in another to rectal troubles; while a third may be traced to wrongs of the genito-uterine system.

Some cases do better under the influence of electricity than upon internal medication.

Where the bradycardia is permanent, tonics will replace stimulants. The patient's general health will need to be restored. Good digestion must be secured in order to make a good blood. For eighteen years I have taught my classes the benefits of a dry diet in correcting wrongs of the digestive apparatus in order to secure a good blood supply. Cactus will prove beneficial in these cases.

The Eclectic Practice of Medicine, 1907, was written by Rolla L. Thomas, M. S., M. D.