Physics Of Mitral Stenosis
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Disturbances Of The Heart
Mitral stenosis, though less common than mitral regurgitation, is a
frequent form of disease of the valves, especially in women. Often
this condition is associated with regurgitation; but in a simple
mitral stenosis the greatest hypertrophy is of necessity in the
right ventricle. The left auricle finds it difficult to empty all of
its blood into the left ventricle during the ordinary diastole of
the heart. This auricle
then somewhat hypertrophies, but is unable
to prevent more or less damming back of the blood into the lungs
through the pulmonary veins. This causes passive congestion of the
lungs, and the right ventricle finds that it must labor to overcome
the increased resistance in the pulmonary artery, and hypertrophies
to overcome this increased amount of work. When this condition has
become perfected, compensation is established and the circulation is
apparently normal. Nature causes these hearts, when they are
disturbed or excited, to pulsate slowly, causing the diastole to be
longer than in a heart with mitral regurgitation. This allows more
blood to enter the left ventricle, and the left ventricle, acting
perfectly on the blood which it receives, causes a good systolic
pressure in the aorta and the systemic arteries. The left ventricle
in this condition does not become hypertrophied. If the heart does
act rapidly and the left ventricle contracts on an insufficient
amount of blood, the peripheral pulse is necessarily small and the
arterial tension is diminished. Very constant in this condition, and
of course noticeable whenever there is pulmonary congestion, is the
sharp, accentuated closure of the pulmonary valve. The lungs on the
least exertion are always a little overfilled with blood. The
pulmonary circulation is always working at a little disadvantage.
The first symptoms of lack of compensation with the lesion of mitral
stenosis are lung symptoms--dyspnea, cough, bronchitis, slight
cyanosis, sometimes blood streaks in the expectorated mucus and
froth, and, if the congestion is considerable, some edema of the
posterior part of the lungs, if the patient is in bed. Sooner or
later during this failing compensation the right ventricle becomes
dilated, and the symptoms of cardiac insufficiency and venous
congestion occur, as described above with mitral insufficiency.
Again, as in mitral insufficiency, if compensation is restored in
mitral stenosis, these symptoms are improved. These patients,
however, are never quite free from dyspnea on exertion. Any
inflammation of the lungs, even a severe bronchitis, is more or less
serious for the patients and their hearts. The mucous membrane of
their bronchial tubes and air vesicles is always hyperemic, and it
takes little more congestion to all but close up some of the
passages. and dyspnea or asthma, or suffocating, difficult cough is
the consequence.