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ON INTERMITTENT PULSE & PALPITATION.
DEFINITION OF INTERMITTENT PULSE.-PHYSICAL CHARACTER.
Definition of Intermittent Pulse.
In relation to time there are in disease three distinct variations in the beat of the pulse.
(1) There is a beat which may be called an acute irregularity, in which each stroke is given in correct order of succession the one stroke to the other, but in series of five, ten, or other number of beats differing in rate from other series. In cases of very feeble heart we often meet this condition, we meet it in anæmia, we meet it after loss of blood and other serious states of depression.
(2) There is a beat which may be called a prolonged irregularity, in which the pulse shall during one minute register say seventy, and if counted through a succeeding minute, ninety or a hundred beats. This form of irregularity, in relation to time, is met with most distinctively in cases of acute cerebral disease, especially in the hydrocephalus of children. In hydrocephalus, according to my experience, it is a fatal sign; I have never known an instance of recovery, when, with other acute symptoms pointing to the brain as the seat of the acute disease, this prolonged irregularity has been markedly present.
(3) Lastly, there is the kind of irregularity which is to be studied in the present essay—the irregularity known to us all, and known to many of the intelligent public, by the term intermittency, and connected often by the patient with the further definition palpitation. This irregularity consists of an absolute loss of certain of the normal beats of the pulse; it is as though the pulse were clipped out for the moment, the intermittency of stroke occurring during the whole interval of a normal stroke, or in extreme cases covering the time of two, three, or even a greater number of natural pulsations.
Three years ago I brought forward these subjects of Intermittent Pulse and Palpitation as one of the lectures in my course of Experimental and Practical Medicine. The phenomenon of intermittency in the pulse stroke of the heart had then been under my observation for many years, and on the facts relating to it, thus learned clinically in the first instance, the lecture was based. It was not however until after the lecture was published that I was conversant of the practical interest which the profession took in the question discussed; and indeed I am in doubt whether any paper I have ever written has, on the whole, created a keener interest. In brief, I struck upon a subject with which all practitioners were acquainted, but respecting which little had either been written or spoken; thus there was excited a general desire and curiosity to receive, even as a novelty, an old and familiar study.
Since the time when the lecture became known in the profession a very large number of cases of intermittent pulse have been brought under my notice. I have consequently been able to re-learn the subject from a position extremely favourable for the labour, and as it embraces many questions of importance relating to physiology and practice, I venture now to revise what I have previously written, and to add such new facts as have been presented to my mind.
Physical Character of Intermittent Pulse.
If we turn to the heart to tell us what is the reasou of the hesitation of the pulse when it intermits, we discover readily enough that the gap is due to a break or holding back of the ventricular systole. We listen for the heart sounds, the Lūb dúp, followed by the pause, and all goes on correctly a given number of times, when suddenly there is, as it were, a revulsion-I know no better term-and with that the hesitation in the arterial beat. We wait for a return of the phenomenon, we analyse it carefully, and we read that it is connected with an entire absence of the first or long cardiac sound, with a very faint second sound, and with loss of the pulse, followed usually by a heavy thud of a returning first sound, by two sharp and distinct but faint quick second sounds, and by return of the pulse
We infer from this reading what has happened in the cardiac mechanism; we infer that the left ventricle, at all events, has, for a moment, failed to contract on its contents, the blood within it. Thus, the column of blood which has been always left in the arteries waiting for ventricular impulse has been reduced passively by mere arterial contraction, and the pulse has been lost, because there has been no wave projected along the artery from the heart. Following on the second of the two succeeding diastolic sounds, the pulse returns; the revived systolic contraction, having first re-supplied the arteries, overcomes arterial tension and reproduces the pulse wave.
It seems difficult at first to account for the two rapid diastolic sounds which follow one upon the other. At one time I thought the double diastolic sound, the quick dúp dúp, was due to the circumstance that at the moment of intermittency the left ventricle of the heart alone fails to contract, and that the double returning second sound is produced by a separate, instead of a simultaneous, closing of the pulmonary semilunar and aortic semilunar valves, the pulmonary valves continuing to act in their proper order, and closing twice in the same time that the aortic valves close once, until the simultaneous action is restored. I am, however, induced, by further research, to believe that this view does not quite correctly explain or define what really occurs, and I therefore beg to offer a revision of the subject in a separate chapter.
CAUSE OF INTERMITTENT PULSE, MECHANICAL AND ORGANIC.
Mechanical Cause of Intermittent Pulse.
When we write the sounds down in order, before, during, and after an intermittent act, thus
intermittency with loss of pulse.
ventricular systole with return of pulse.
Lūb dùp 0 0 dúp 0 Lub dúp dúp Lub dúp 0 the phenomenon of intermittency is seen clearly enough, I think, as dependent on failure of the action, I will say first, of the left ventricle. In what does that failure consist? Does the ventricle not contract, or does it contract and find no blood upon which to close ? The evidence on this point is very sound. It goes at once to show that the ventricle does not contract; if there were no blood in the ventricle, there must be blood in excess in the pulmonary circuit and in a hugely distended auricle, of which conditions we have no indications whatever. That is the negative side; but there is positive, almost speaking, evidence of what has occurred in the long thud of the returning systolic sound which proclaims the ventricle again at its work, and which tells that it is contracting on a more than ordinary volume of blood within its cavity. If these evidences, then, be true, the intermittency of the arterial pulse occurs from an independent failure of action of the left ventricle of the