Sources: Disturbances Of The Heart
If the pulse is intermittent and there is apparently a heart block.
Stokes-Adams disease should be considered as possibly present, and
digitalis would be contraindicated and would do harm.
A scientific indication as to whether a heart is disturbed through
the action of the vagi or whether the disturbance is due to muscle
degeneration may be obtained by the administration of atropin.
Talley [Footnote: Talley, James: Am. Jour. Med. Sc., October, 1912.]
of Philadelphia shows the diagnostic value of this drug. It is a
familiar physiologic fact that stimulation of the vagi slows the
heart or even stops it. Stimulation of these nerves by the electric
current, however, does not destroy the irritability of the heart;
indeed, the heart may act by local stimulation after it has been
stopped by pneumogastric stimulation. It is also a well known fact
that anything which inhibits or removes vagus control of the heart
allows the heart to become more rapid, since these nerves act as a
governor to the heart's contractions. Under the influence of atropin
the heart rate is increased by paralysis of the vagi. Talley states
that a hypodermic injection of from 1/50 to 1/25 grain of atropin
produces the same paralytic and rapid heart effect in man. He
advises the use of 1/25 grain of atropin in robust males, and 1/50
grain in females and in less robust males, and he has seen no
serious trouble occur from such injections. The throat is of course
dry, and the eyesight interfered with for a day or more, but Talley
has not seen even insomnia occur, to say nothing of nervous
excitation or delirium. Theoretically, however, before such atropin
dosage, an idiosyncrasy against belladonna should be determined.
The value of such an injection rests on the fact that atropin thus
injected will increase the normal heart from thirty to forty beats a
minute, and Talley believes that if the heart beat is increased only
twenty or less, if the patient has not been suffering from an
exhausting disease, it shows "a degenerative process in the cardiac
tissue which makes the outlook for improvement under treatment
unpromising." He also believes that when the heart in auricular
fibrillation is increased the normal amount or more than normal, the
prognosis is good. He still further advises in auricular
fibrillation an injection of atropin before digitalis has been
administered, and another after digitalis is thoroughly acting.
Comparison of the findings after these two injections will determine
which factor, vagal or cardiac tissue, is the greater in the
condition present. The patients with a large cardiac factor are the
ones who may be more improved by the digitalis treatment than those
in whom the fibrillation is caused by vagus disturbance.