Definition:—A condition of the action of the heart in which the pulsation is much slower than normal, although usually regular and uniform in rhyme and rhythm. In extreme cases the pulse may be slowed to twenty-four beats per minute. I have known of several cases in strong men where the usual beat was forty-six per minute, or below. This may result from conditions which are entirely the opposite of those which induce tachycardia, or in extreme cases the two conditions may be due to similar causes. They are apt to occur following protracted fevers and acute exhausting disease. Conditions that result in uniform weakness of the entire system, may induce it. It may also be caused by any influence that will cause and maintain an undue rise in arterial pressure. It results from the physiological action of opium, from lead poison, and from poisonous alkaloids, which act as motor depressants. It is a normal condition following labor. Diseases which may be followed by slow pulse are apoplexy, with resulting paralyses, meningitis, cerebral tumors, syphilis, myxedema, and chronic asthma and emphysema. It occurs as a result of disease of the coronary arteries, in fatty degeneration of the myocardium, and, occasionally, in aortic stenosis. It occurs in insane patients also, and in melancholia.
Symptomatology:—When the condition occurs in paroxysms, the onset is sudden, but in most cases the condition is one of gradual development and gradual termination. Usually but few symptoms appear in protracted cases, the patient's habits will be observed to be sluggish, with mental inactivity, and there may be some difficulty of breathing, which is increased upon violent action, but few other symptoms are observed unless there is vertigo, or occasionally, attacks of unconsciousness. In paroxysms, the onset may be marked by extreme vertigo, with syncope, unconsciousness, continuing for a varying length of time, with sluggishness of every function of the body, which does not readily respond to stimulation. The pulse varies from the slow, round, full beat, of perhaps from forty to twelve beats per minute, to a small, weak, easily compressible pulse, which will beat from sixty to forty beats per minute. The action of the heart, while slow and regular, may be greatly increased in force, the contractions being much more violent than normal; and yet the pulse wave may not be perceptible at the wrist, and the heart sounds will be feeble.
Treatment:—The patient must be removed from all conditions which may cause a violent impression to be made upon the nervous system; must be placed in a condition of rest and extreme quietude. Attention to the functional operation of the various organs of the body must be the same as those advised for other serious heart disorders; at the same time, the nervous system must be subject to the influence of the most potent restorative tonics. Stimulants given for their immediate influence must be administered with great care. Where the temperature has fallen with the reduced pulse beat, I have obtained excellent results from an alteration of cactus and strychnin, both in small doses. Hydrastis, collinsonia, small doses of nitroglycerin, and well selected stimulating tonics may be administered. No specific measures are as yet available.