382 HEART DISEASES [VOL.VI
sen es as a gauge to measure the amount of oxygen the patient is getting.
The gas should pass through the water at a rate of at least five bubbles
per second.
Blood-letting to the extent of 10 to 20 ounces may prove a life-saving
measure in acute heart failure. The special indications for employing
this treatment are venous engorgement with cyanosis and acute pul-
monary oedema.
(4)—Surgical Measures
Certain surgical measures which have been employed in the treatment
of heart failure merit consideration, though they must still be regarded
Tfyruid- as being in the experimental stage. Complete thyroidectomy by lowering
ectomy fae basal metabolism reduces the heart's liabilities, and might therefore
be indicated on theoretical grounds. In congestive heart failure the
results of this operation ha\e not corne up to expectation, but in angina
S\mpath- they have been more promising. Operations such as sympathectomy
tctomy serve to reiieve pain? but whether these procedures are justified appears
doubtful, for pain in angina is a danger signal which warns the patient
that lie is overtaxing his heart; if therefore the pain is relieved without
eradicating the cause of the disease, an important safeguard may be-
renioved.
(5)—Summary
In Fig. 57 I ha\e attempted to summarize diagrammatically the
therapeutic possibilities in the treatment of heart failure of the
ischaemic type. A similar diagram could be devised for the congestive
type.
In the normal healthy subject (I), the cardiac reserve (A-E) far exceeds
the basal resting requirements of the body (E-F). In the patient with
angina (II), on the other hand, the cardiac reserve (C-D) is greatly
reduced. The reduction is in part attributable to impaired efficiency
of the heart (A-C). This depends on various factors, of which the most
important is insufficiency of the coronary circulation (A-B). Structural
changes in the coronary arteries and in the myocardium are permanent
and therefore beyond the scope of therapeutic measures. But, as has
been pointed out above, the nervous factor is of great importance in
determining not only the sensitivity to pain but also the liability to
attacks. This can be, in part at least, controlled by cerebral depressants.
Similarly, toxic factors affecting the myocardium, such as tobacco and
focal sepsis, may be eliminated. By these means efficiency of the damaged
heart can be increased from D-C to D-C'. It may be hoped, by suitable
treatment, to lighten to some extent the load imposed upon the heart
by such factors as obesity and high blood-pressure, thereby increasing
the cardiac reserve from C-D to C-D'. That marks the limit of possible
therapeutic achievement. When it has been attained, the patient must be
content to adapt his mode of life to his reduced exercise tolerance C'-D'.