Simple, eccentric, concentric. Usually eccentric. Causes, effusion in
pericardium, obstruction of coronary arteries, by false membranes,
etc., general inanition. Symptoms, beats weak, sounds loud, clear,
decreased area of dulness on percussion, pulse slow, weak, under
excitement unequal, irregular, intermittent with palpitation, dropsy
of limbs, etc., murmur with 1st sound. Treatment only in early stages
by removal of the cause.
The loss of substance in the muscular walls of the heart is either
_simple_ when there is no change in the capacity of its different
cavities:—=eccentric= when the chambers of the heart are enlarged; or
=concentric= when these chambers are reduced in size. Like hypertrophy
it may affect the walls of one chamber to the exclusion of the others.
Atrophy is much less frequent in the lower animals than hypertrophy and
in nearly all cases on record it was associated with dilatation.
The _causes_ are not always very evident. Effusion into the pericardium
is one of the most frequent, the compression of the heart impairing its
nutrition and decreasing its size. Especially is it hurtful when several
layers of false membranes deposited on the surface of the heart become
organized, preventing its sufficient dilatation and compressing its
nutrient bloodvessels. A case of this kind in a dog occurred to Leblanc;
the right auriculo-ventricular opening was surrounded by thick organized
layers of false membranes which by their contraction had largely
diminished the opening and even pressed on the coronary artery cutting
off to a great extent the supply of blood to the walls of the ventricle.
Another alleged cause is a prolonged insufficient nourishment to the
entire body. Leblanc has also observed this in dogs the subjects of long
continued wasting maladies.
_Symptoms._ In pure atrophy these are the opposite of those seen in
hypertrophy. The beats of the heart are weak or inappreciable to the
hand placed on the side of the chest behind the left elbow. The sounds
of the heart are loud and clear, their intensity being proportionate to
the thinning of the walls and the dilatation of the chambers. Percussion
so far as it can be made effectual, which is chiefly in dogs, shows a
diminished area of dulness. The pulse is slow, weak, or indistinct,
compressible, becoming accelerated, unequal, irregular, and intermittent
when the patient is excited. Palpitation is frequent, breathing is
difficult or easily embarrassed and there is a tendency to dropsy of the
limbs and dependent parts. These symptoms are usually associated with
considerable prostration and depression.
These are often complicated by symptoms of valvular disease or
dilatation.
Atrophy progresses slowly and rarely causes death in the earlier stages.
In its advanced stages when dropsy has supervened little can be done
even in its mitigation. In the earliest stages only can good be done by
employing measures calculated to remove its causes and thus put a stop
to its progress.