Simultaneous examination of the two radial arteries may show delay and altered character of the pulse on the affected side.

Sphygmogram. The percussion wave is absent. The ascending limb of the tidal wave is of low amplitude and rises slowly. The apex is rounded, and the descending limb falls gradually. The dicrotic and secondary waves are usually absent (Fig. 27).

THE

INSTRUMENTAL

THE BLOOD

DETERMINATION
PRESSURE

OF

The digital estimation of the blood pressure obtained from a peripheral vessel like the radial artery is liable to several fallacies which may mislead even the well-trained finger (Oliver). In order to ensure accuracy of observation, and also to provide a record for the purposes of comparison and reference, it is necessary to employ other means of gauging the blood pressure. Instruments which fulfil these requirements have been devised by Hill and Barnard (the Sphygmometer); also by Oliver (the Hæmodynomometer), and by others. The estimation of the blood pressure by both instruments is obtained through a fluid medium, and herein lies the accuracy of the method.

The sensitiveness and accuracy of these instruments have been thoroughly tested, and though the results obtained are not beyond dispute, it is not too much to say that a blood pressure gauge should form part of the equipment of every clinician. Both the arterial and venous blood pressures are capable of measurement. Oliver states that if the influence of gravitation be excluded the arterial blood pressure is practically uniform throughout the arterial system. The average mean arterial pressure varies between 90 and 110 c.mm. Hg. It is modified by the age, weight, and build of the individual. The average venous pressure in recumbency Oliver puts at 10-20 c.mm. Hg.

CHAPTER V

THE CARDIOGRAPH

Its Sphere of Usefulness-The Normal Cardiogram-Cardiograms of the Chief Valvular Lesions.

THE value of the cardiograph as a means of diagnosis even in skilful hands is somewhat problematical, and in any case the results obtained are decidedly less trustworthy than those afforded by the sphygmograph. The apex beat is often difficult or impossible to define, and unless the button of the instrument is accurately applied over the site of its manifestation, the tracing obtained is not that which is due to the actual impulse of the heart against the chest wall, but to movements in the neighbourhood of the apex beat which give the so-called "inverted tracing." If the operator is not aware of this possibility his results may be quite unintelligible.

Provided, however, that an accurate and reliable tracing can be

F=Closure of semilunar valves and commencement of diastole

K = Elevation due to sudden filling of ventricle by the active dilatation of its walls

/ = Period of passive filling of ventricle

a=Auricular systole and completion of the process of filling the ventricle

a-d-Sudden rise of lever due to contraction of the ventricular wall at the commencement of systole

d=Sudden opening of aortic valve

def Continued contraction of ventricular wails

f=Closure of aortic valve

Note.-a-f-systole

f-a-diastole

obtained, an intelligent interpretation of the cardiogram may afford diagnostic evidence of some value. For instance, the relative lengths of the diastolic and systolic periods of the ventricular cycle may be gauged by this means with some accuracy. In mitral stenosis and in dilatation of the left ventricle the diastole is relatively prolonged, whereas in aortic regurgitation and in hypertrophy of the ventricle the same period is relatively shortened, and hence the cardiographic evidence in the differential diagnosis of these affections may be requisitioned with advantage.

In describing a cardiogram it is perhaps simplest to make use of the same nomenclature as was employed in the account of the sphygmogram.

Thus a cardiogram may be said to consist of an ascending limb or upstroke (k-d), an apex (ade), and a descending limb or downstroke (d-g).

kla = diastolic rise; a-d-systolic rise
d-f-systolic fall; f-k-diastolic fall

The Ascending Limb

It will be noticed that this portion of the curve comprises both diastolic and systolic rises. The first part of the diastolic rise generally shows an elevation (k) which marks the filling of the ventricle by its active dilatation. This elevation is particularly well marked when the dilatation of the chamber is energetic as in (1) hypertrophy of the heart with powerful suction action on dilatation; (2) low degrees of blood tension with rapid systole and sudden relaxation of the ventricle.

Immediately following the elevation k is a gradual ascent of the upstroke 7. It represents the passive filling of the ventricle between the first inrush of blood, due to its active dilatation, and the final act of filling by the auricular systole a. The steepness and length of this part of the curve depend largely on the total length of diastole; when diastole is prolonged this section of the curve is extensive and the rise gradual. When diastole is short the opposite conditions obtain. The diastolic rise sometimes shows elevations in addition to k and a. These represent irregular contractions of the auricle, or are due to vibrations of the auriculoventricular valves.

The elevation a at the end of the diastolic rise is due to the auricular systole, and is specially well marked when the left auricle is hypertrophied as in mitral stenosis.

As a rule the elevation a is followed by a notch, which separates the diastolic from the systolic rise. Sometimes, however, this notch is absent, in which case the diastolic and systolic rises are continuous. The systolic rise varies in amplitude in different cases. Its height, however, depends more on the suddenness of the ventricular systole than on its force. Thus in palpitation and cases of low-tension

pulse the amplitude of this portion of the tracing may be very great, whereas in hypertrophy the rise may be comparatively small.

The Apex

The degree of acuteness of this angle depends chiefly on the suddenness with which the ventricle empties itself, and is due to the falling away of the heart's apex from the chest wall. It is especially acute in mitral regurgitation, in which condition the ventricle has two outlets by which it can empty itself, viz. through the incompetent mitral valve and through the aortic orifice.

The Descending Limb

f marks the completion of the systole, and the distance (d-f), i.e. the systolic fall, is a rough measure of the length of the systole. In hypertrophy of the heart, and in aortic stenosis, this section of the curve is of considerable extent, and the apex is usually more or less rounded.

f-k, the diastolic fall, marks the beginning of diastole immediately after the closure of the semilunar valves. It is usually nearly perpendicular, and occupies, consequently, a very short period before the filling of the ventricle causes the diastolic rise.

The characteristic features of the cardiograms taken from cases representing the chief forms of valvular disease will now be briefly considered.

MITRAL STENOSIS

The diastolic rise is usually prolonged, and the elevation in it due to the auricular systole is well marked. There may be secondary elevation on this limb of the cardiogram, due to the causes enumer ated above.

In this tracing the diastolic rise is of considerable length and inclined obliquely upwards, showing the long period occupied in

the filling of the ventricle through the narrowed mitral orifice. Secondary undulations are present on this section of the tracing, due to irregular contractions of the auricle, or to vibrations set up at the mitral valve. The elevation due to the auricular systole is not sufficiently well marked to suggest great hypertrophy of the left auricle.

This tracing shows great irregularity of the heart's action, which is due to the supervention of heart failure with tricuspid regurgitation.

This tracing shows a great elongation of the "diastolic rise" section of the ascending limb.

MITRAL REGURGITATION

را

FIG. 33.

CARDIOGRAM FROM A CASE OF MITRAL REGURGITATION
(Sansom)

This cardiogram shows great irregularity of the heart's action. The length of the diastolic rise is very variable, and the rise due to the auricular systole is badly marked. The apex is bifid, the

H