and the venous pressures. This point has been dwelt upon by Bishop1 who states that failure of the circulation in heart disease becomes a matter of concern only when the patient resumes his occupation and even then a low systolic pressure should not be regarded as serious except when it is but little above the venous pressure.

CARDIAC LOAD AND OVERLOAD

Willard J. Stone2 has devised a formula whereby the degree of cardiac load and overload may be determined and expressed in comparable figures. This study is based upon the assumption that clinically the pulse pressure represents the load of the heart, which under normal conditions approximates 50 per cent. of the diastolic pressure. The systolic and pulse pressures represent myocardial values, while the diastolic pressure represents arterial resistance and is therefore the arterial factor. The foundation for this contention is based upon a study of sixty-one normal persons whose average pressures were systolic 123, diastolic 80, pulse pressure 40. The amount of energy expanded, therefore, to maintain the circulation in excess of that required to open the aortic valve, i.e., overcome peripheral resistance of 80 was 40 (see also my normal chart, page 117). The normal load, therefore, may be considered 40 or 50 per cent. of the diastolic pressure. In twenty-one acute infectious cases that recovered the average pressure was systolic 119, diastolic 76, pulse pressure 42, the load in this case being 4246 or 55 per cent. On the other hand in five fatal acute infections the averages 1 "Heart Disease and Blood-pressure," 1907. Jour. A. M. A., Oct. 4, 1913, lxi, 14, p. 1256.

were systolic 102, diastolic 68, pulse pressure 34, and the load 3468 or 50 per cent.

Preceding circulatory failure, there may be a radical change in the readings, with a tendency for the pulse pressure to equal or exceed the diastolic. Thus in six of fourteen decompensated myocardial cases the pulse pressure approached or exceeded the diastolic. From this it appears that with a load factor of 50 plus an overload of 50 per cent. (i.e., when the pulse pressure equals the diastolic) there is great danger of myocardial failure. Another condition enters here, which is the commonly associated rapid heart rate, which Henderson and Barringer1 have shown to be a factor. A rapid heart shortens the diastolic period and interferes with ventricular relaxation, thereby preventing the proper filling of the ventricle and in consequence the systolic output is diminished and the mass movement of blood impaired.

Another method of determining myocardial efficiency has been suggested by Masing2 who notes the effect of exercise upon the relation of systolic to diastolic pressure. After exercise a normal circulatory apparatus will yield a systolic rise of greater extent than the diastolic rise, i.e., the pulse pressure is increased, while after exercise a defective myocardium may show the rise in both pressures, but they will tend to approximate and consequently the pulse pressure will be reduced. In my experience this change cannot always be demonstrated, although in certain cases it is undoubtedly so.

1Y. Henderson and T. B. Barringer, Am. Jour. Physiol., 1913, xxxi, p. 288.

2 E. Masing, Deutsch. arch. f. klin. Med., 1902, lxxiv.

In this the increase in the value of the fraction is an indication of efficient heart, while the decrease in the value of the fraction after exercise is an indication of inefficiency.

In my own practice I have derived much satisfaction from a computation, first suggested by Gibson, in which an effort is made to demonstrate the relative work and velocity factors of the cardiac energy, modified to meet the conditions met in auscultatory determinations.1 This is based upon the following propositions: First, the normal systolic, diastolic, pulse pressure relation is 3:2:1; and second, if the pulse pressure represents the systolic output (see page 137) it follows that it must also be the most important factor in determining the velocity of the blood-stream, which for physical reasons must bear a definite relation to the volume output of the heart and to the caliber of the conduits the arteries-so that, if other factors remain the same, it is not a difficult matter to estimate both the velocity and also the work of the heart while operating under either normal or abnormal conditions.

2

The above propositions can be arranged graphically as follows. For example, take a case presenting these figures: S.P. 130, D.P. 85, P.P. 45, P.R. 70; then - P.P. (45) × P.R. (70) Velocity (3100), and S.P. (130) X P.R. (70) Work (9100).

=

=

We may carry our calculations further and state that the

1 Interstate Med. Jour., p. 897, xxi, 8, July, 1914.

2 F. A. Faught, Interstate Medical Journal, July, 1914.

FIG. 69.-Female. Aged sixty. Typical cardiac neurasthenic. Has been in the hands of many physicians during the past ten years with indifferent results. Complains of a long list of vague and variable symptoms including insomnia, joint pains, globus hystericus, dyspnea, heat-flashes, palpitation, variable appetite and nervousness.

Physical examination shows a moderate degree of chronic myocarditis which is well shown in the chart by the abnormally large pulse pressure. At no time during observations did this patient show any marked signs of myocardial weakness, the condition being more one of instability.

At (A) a sharp rise in systolic and pulse pressure was accompanied by a number of dizzy spells and a tendency to faintness, the cause for which was unexplained. A prompt fall in pressure resulted from an administration of atropin with strychnin, followed by effect obtained at (B), due to better hygiene and systematic out-door exercise. This was the only time during the observation of this patient that the symptoms were suggestive of myocardial overstrain. This is the type of case which, on account of extreme personal solitude, and the avoidance of all unnecessary strain that would tend to upset a circulatory equilibrium will go on for years and may live to extreme old age in spite of the cardiac-muscle handicap.

Fair cardiac efficiency is indicated by the regularity with which the pulse pressure follows the systolic.

velocity and the work, as estimated by the above formula, also bear a definite normal relation which is dependent entirely upon the normal relation of pulse pressure to systolic pressure (and that this relation is as 3:1, while in myocardial cases the ratio is increased).

Application.-Case of chronic myocarditis and arterio

sclerosis.

Before treatment:

S.P. 210, D.P. 100, PP. 110, P.R. 104.

S.P. (210) X P.R. (104)

=

Work (21,840)

P.P.(110) XP.R.(104) = Velocity (11,440)

After two weeks' treatment:

S.P. 195, D.P. 140, P.P. 55, P.R. 84.

S.P. (195) XP.R. (84) Work (14,580)

=

=

=

= ratio 1:3.

Here under the proper method of treatment the work velocity was greatly benefited, the actual work reduced one-third, so that while the heart was at first barely able to maintain the needs of the case under serious strain, accompanied by evident signs of cardiac distress, after two weeks the danger of acute failure of the circulation was overcome and the whole complexion of the case altered for the better.

Importance of Diastolic Pressure. From his study Stone concludes that since the diastolic pressure measures the peripheral resistance, it is a better index of hypertension than is the systolic pressure. The diastolic pressure is less influenced by pathologic factors than the pulse pressure.

Pulse Pressure in Cardiac Neuroses.-Stone believes that marked variations of pulse pressure occurring at