Original Articles.

THE PRESPHYGMIC INTERVALOR TIME REQUIRED TO START THE ARTERIAL PULSE AFTER THE BEGINNING OF THE SYSTOLE

OF THE VENTRICLE."

BY A. T. KEYT, M. D., CINCINNATI, OHIO

A DEGREE of asynchronism between the beat of the heart against the chest-wall and the carotid pulse is discernible to the delicate and practiced touch. Such interval is more plainly shown by the use of two instruments, constructed on the principle of Herrison's sphygmometer, and supplied with elastic tubing of equal and convenient length to permit the glass tubes to be placed side by side for ready observation. When the pulse bases are in position, one on the heart and the other on the artery, the liquid columns first strike the eye as oscillating in alternation, one ascending while the other is descending, and vice versa. Observations to this effect, and by the means just described, were made by Dr. Scott Alison in 1856.2

The sphygmometric part of my differential or compound sphygmograph utilizes the principle of Herrison's instrument, and with it I have observed, time after time, when the bases were placed respectively on the heart and carotid artery, that the liquid columns appeared to rise and fall in alternation. Close inspection, however, discloses that the relation of these movements is not one of perfect alternation, but of succession.

Happily we now have the graphic method which not only demonstrates the succession of the cardiac and carotid pulsations, but permits us, also, to measure with precision the duration of the cardio-carotid interval.

The experimental proof that a cardiogram taken from the chest wall represents the phases of the cardiac revolution, and that the basal point of the main ascent marks the beginning of cardiac systole, has been furnished by Marey in one of his celebrated experiments on the horse. Simultaneous inscriptions of the blood pressure in the interior of the right ventricle, and of the heart's action against the chest wall, showed correspondence with each other in the essential points, and exact synchronism in the beginning of the two upstrokes. Marey also demonstrated, in an experiment of his series on the horse, that the two ventricles begin to contract precisely at the same time; and in another place he states that he has never observed default of synchronism between the two ventricles. Thus we are prepared to accept the cardiograms obtained from the chest wall of man as correct representations of the movements of the human heart, and, especially as concerns the present investigation, to accept the basal point of the main ascending line as marking the beginning of ventricular systole. In yet another experiment of Marey's series on the horse, one sound was lodged in the left ventricle, and another in the aorta just above the valves. The inscriptions thus obtained showed that the blood pressure in the ventricle began to rise a notable time before the beginning of the rise in the aorta. The interval between these beginnings represents the time elapsing after the ventricle begins to contract until the aortic valves open and the blood begins to escape into the artery. This is the pre

1 Read before the Cincinnati Medical Society March 23, 1880. 2 The Lancet, Am. Ed., 1856, page 526; 1857, page 240.

As it has been proved that the pulse wave rises later in an artery removed from the heart, evidently observations between the heart and an arterial point beyond the root of the aorta will give a time difference, made up of the presphygmic interval and the time required for the pulse wave to travel from the aortic orifice to the point designated, the transit time of the pulse wave.

To determine the duration of the presphygmic interval in man, simultaneous tracings of the heart and carotid pulse are obtained with an accompanying chronogram, or in the presence of a known velocity of the surface receiving the inscriptions, and the time difference thus ascertained is noted. Next, the transit time between the aortic orifice and carotid point is determined by a method presently to be described. The latter time deducted from the former gives the presphygmic interval.

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The duration of the heart-carotid interval in man has been investigated. Czermak in 1864, by means of his photo-sphygmograph, measured the interval at .087 second. Mosso, by means of a cardiograph for the heart and a tambour device for the carotid pulse, measured the interval at between 10 and 11 hundredths of a second.

By means of an apparatus of great convenience and accuracy, consisting of two uniform sphygmographs of transmission and a chronograph, all writing on the same smoked slide, I myself have made a very large number of observations and measurements of the heartcarotid interval. I believe that I have the advantage of other experimenters in the facility with which I make these observations, and my method employed with reasonable care admits of no material fallacy. My results demonstrate:

(1.) That the interval is subject to considerable variation in the same individual, and in different individuals compared with each other. See cuts Nos. 16, 23, 56.

(2.) That the interval varies inversely with the pulse rate, directly with the pulse duration. See Nos. 16, 37, 56, all from the same person.

(3.) That the average duration of the interval, with pulse at 75 to the minute, four fifths of a second long, is about .08 second.

According to these data, a pulse of 60, one second long, will give the interval one tenth of a second, and the rule may be formulated that the average cardiocarotid interval is one tenth the duration of the pertaining pulsation. This rule is approximate only, for the interval varies from other factors besides pulse frequency; nevertheless, I have found it of practical value in determining approximately what should be a standard time difference for a given pulse rate.

Accepting, then, .08 second as a standard heart-carotid interval in health, with pulse at 75 per minute, in pur

8 The Proceedings of the Royal Society, No. 157, 1875, page 144. dem privat Laboratorium, in Prag, 1864. 4 Med. Chir. Rev., January to April, 1865; from Mittheilungen aus

6 Die Diagnostik des Pulses, Leipzig, 1879, page 45.

6 The accompanying engravings are used to illustrate, in a general way, an indefinite number of observations. My deductions are based upon my whole experience, and in some instances statements in the text do not exactly accord with expressions of the plates. The discrepancies, however, are few and small, and I can say that my larger experience confirms, in a remarkable manner, the results of my earlier work.

suance of our investigation, we now seek a standard transit time of the pulse wave over the arterial tract included. As the aortic root is not accessible for observation in man, obviously the desired data must be arrived at indirectly. This is the method: The velocity of the pulse waves over other arterial tracts is ascertained, and if these are found to differ, the velocity over the arterial tract most nearly corresponding with that between the aortic root and carotid point is selected as the basis for computing the cardio-carotid transit

The mean average velocity of the pulse wave from the carotid point to the dorsalis pedis is 361 inches per second; from the carotid to the radial 290 inches per second; from the carotid to the femoral 269 inches per second; from the femoral to the dorsalis pedis 464 inches per second.

Thus the pulse-wave velocity over different arterial tracts is shown to vary in an important sense. The tract between the carotid and femoral is most closely allied to the tract between the aortic root and carotid; the similarity, indeed, is very intimate; accordingly, we utilize for our purpose the carotid-femoral pulse-wave velocity.

The measurement of the arterial length between the aortic root and carotid point is placed at 7 inches. Hence 5 6 s = .026 second expresses the duration of the interval sought.

The pulse-wave velocity, as has been determined, though differing considerably in different individuals, in the same individual is subject only to a limited variation, even under considerable changes of the circulation, and variations of pulse frequency exert upon it no appreciable disturbance. (The latter fact has also been demonstrated by Garrod.) Therefore, for the short distance of 7 inches, .026 second may stand as an approximate quantity to express the cardio-carotid transit interval for any pulse rate or order of conditions, aortic aneurism alone excepted.

rapidly the presphygmic interval as the pulse increases in frequency, and at 170 to render it nil. Garrod's results from his equations make the presphygmic intervals much shorter throughout, and the rate of reduction more rapid than mine.

My observations do not, as yet, enable me to determine the limit of pulse frequency on the one hand, and of infrequency on the other, at which the cardio-carotid interval ceases to vary, as enunciated, inversely with the pulse rate: between 120 and 60 I am quite sure the rule holds; beyond these there appears to be uncertainty.

By my rule of reduction the presphygmic interval would become nil at 230, and at 180 it would be yo of a second; yet it is scarcely possible that it should become nil even if the former rate could be reached, and the probability is that the shortest permissible interval would exceed that just mentioned.

The variations of the presphygmic interval will bear further elaboration. It often varies in the same healthy person at the same sitting with the same pulse rate; but the range under such circumstances is limited. The explanation of this variation I find in the incessant minor changes in the manner of the heart's movements and relative changes of blood pressure in the ventricle and aorta: at one systole the contraction is quicker, shortening the interval; at another it is slower, lengthening the interval; at one ventricular discharge the arterial pressure is higher, delaying the opening of the valves; at another it is lower, precipitating the opening of the valves. The reality of these incessant changes is exemplified in the cardiac rhythmic changes my observations 2 have shown to take place, changes in successive pulsations and successive systoles and diastoles in hearts whose action appeared the most regular.

The interval varies more notably in different healthy individuals with the same pulse rate. This fact finds its explanation in individual characteristics, the same as a pulse rate, or pulse form, or quality of the heart's action, peculiar to different persons.

But as before presented the great variations are corelative with the variations of pulse rate. A difference of a few beats per minute may not cause a difference of interval sufficient for certain measurement by present means; yet, other things being equal, it is probable that any change of pulse frequency changes the presphygmic interval. A variation of ten per minute will almost always show a notable difference in the interval. (See No. 56.)

This correspondence between the presphygmic inter

But, inasmuch as the presphygmic varies largely, and the transit for the short arterial length in question inappreciably (aneurism excepted), the cardio-carotid interval practically represents the presphygmic.

Garrod, studying this subject from a basis of experimental observation of the cardiac and radial pulsations, arrived at the theoretical conclusions that the cardiac systole varies inversely as the square root of the pulse rate, and the cardiac systolic portion of the pulse varies inversely as the cube root of the pulse rate; the operation of these rules being to reduce

1 New York Medical Journal, February, 1878; Cincinnati Clinic, April 13, 1878.

nificant fact, and one of a distinctive group we had never known but for the precision of the graphic method. In explanation, to my mind the interval shortens as the pulsations shorten, because: (1.) The abbreviation of the cardiac pulsation tends to abbreviate all its component parts. The length of diastole is markedly diminished as the pulse rate is increased, and the length of systole, although not so regularly corresponding as diastole to moderate variations of pulse rhythm, nevertheless, is found shorter in frequent than in infrequent pulses. The presphygmic interval, being a component part of the cardiac pulsation, is naturally proportional to its duration. (2.) In frequent pulsations the cardiac muscle contracts quicker, and

2 New York Medical Journal, July, 1878; Cincinnati Lancet and Clinic, August 31, 1878.

more rapidly raises the ventricular blood pressure to the point of forcing the aortic valves. (3.) The accelerated blood current in its passage through the heart, with the usually free passage through the capillaries, constantly tends to surcharge the ventricle and deplete the arteries, thus favoring the earlier opening of the valves.

THE VARIATIONS OF THE PRESPHYGMIC INTERVAL IN DISEASE.

The duration of the presphygmic interval varies immensely in disease. The clinical bearings of these variations are in process of development. Already, facts of exceeding importance have been ascertained. Thus it has been demonstrated that the cardio-carotid interval, which, as shown, stands for the presphygmic, is remarkably increased in mitral regurgitation. I have measured the interval in a considerable number of cases of mitral insufficiency, and always found abnormal delay of the carotid pulse; nor have I yet found it absent in any case in which there was a positive diagnosis of this lesion.

idea of sufficiently free regurgitation through the mitral orifice to account for the very great pulse retardation. Thus I am convinced that an important part of the delay in question was contributed by the heavy aortic valves.

The case of Chris. H.,2 aged thirty-one years, presented the greatest pulse retardation I have ever observed. He had systolic murmur accentuated both at the apex and second left interspace, and his post mortem showed mitral insufficiency, thickened yet competent aortic valves, and two considerable aneurismal pouches near the origin of the aorta. Simultaneous tracings of the heart and subclavian arteries showed two fifths (3) of a second as the delay of the subclavian pulse on the heart. In this case a part of the enormous delay was due to the aneurisms, but unquestionably the much larger part was due to the mitral insufficiency and heavy aortic valves.

Yet another important fact has been developed by François-Franck, who has shown in opposition to authoritative teaching that the cardio-carotid interval is shortened in large aortic insufficiency. When opportunity presents me to measure the interval in a case of free aortic reflux, I confidently expect to confirm M. Franck's observation; for in this condition the base of the arterial column rests against the sides of the ventricle instead of against the aortic valves, and is ad

In the case of S. R., aged twenty years, whose clinical history and physical signs afforded positive evidence of mitral regurgitation, the cardio-radial interval measured .222 + or second. (See No. 47.) Deducting from this .0714 second, as the more usual carotid radial time difference, gives .1508 second as the near approximation of the heart-carotid interval in this case with pulse at 80. This will be noted as twice the normal interval at the given pulse rate.

Again, it has been demonstrated that the carotid pulse is abnormally delayed on the systole of the ventricle in that state of the aortic valves designated as heavy, the condition in which, owing to organic changes, their play is sluggish and they open with difficulty.

The case of Dena H., aged thirty-one years, presenting mixed cardiac murmurs, basic and apex, systolic and diastolic, and revealing post mortem the aortic valves loaded with enormous vegetations and the mitral valve incompetent, gave for the heart-carotid interval .25 or second, with pulse at 100. (See Nos. 51 and 52.) Obviously, this is about four times the normal measurement at the pulse rate given. It may be thought that the demonstration fails, inasmuch as the delay might be charged wholly to the mitral reflux; but the pronounced systolic murmur with thrill at the second right interspace, and the heavy state of the aortic valves found after death, prove that great difficulty existed at the aortic opening, while the form of the pulse trace its amplitude, tension, height, and fullness of the second wave - is inconsistent with the

1 New York Medical Journal, July, 1878; Cincinnati Lancet and Clinic, August 31, 1878.

ment of ventricular contraction, insuring thus a short interval between cardiac systole and arterial expansion. Indeed, in a typical case of open aortic valves I expect to find the carotid pulse delayed on the ventriculur systole little, if any, more than the transit time of the pulse wave between the points concerned.1

The remarkable range of variation of the cardio-carotid interval in disease, thus demonstrated, in the face of the comparatively very small variation in health opens the way for new and invaluable additions to our diagnostic resources. The few facts presented afford positive and precise indications of the existence and gravity of certain cardiac valvular lesions, and are an earnest of the rich harvest of results that may be expected to follow this line of observation.

In further remark as to the facility with which these observations are made, I will say that with my combined instrument I make them as readily as I would conduct an ordinary physical examination of the heart. The patient is not annoyed, but usually pleasingly interested in the procedure. The apparatus is sufficiently simple, its adjustments are easily made, and with due care any one with a steady hand may soon learn to use it with entire success.

EXPLANATION OF THE PLATES.

The three tracings on each cut were taken simultaneously; the lowest one being a chronogram, marking fifths of seconds between the points.

distance between the basal points of the respective pulsations

The space between the lines B and C shows the difference of

and the signal lines A, A'; the figures near express the value of this difference in fractions of a second as measured on the

2 New York Medical Record, February 14, 1880. 8 Comptes rendus Ac. Ss. t. xxxvii. p. 296.

4 Since the above was written, by the kindness of Dr. C. G. Comegys, I have been permitted to trace a case in the Cincinnati Hospital diagnosed by that able clinician as one of aortic insufficiency. The tracings show the characteristic features of this lesion and a cardio-carotid interval of one thirty-second of a second, with pulse at 100.