Page 118 - Clinical Pearls in Cardiology

106 Clinical Pearls in Cardiology

There are some conditions, which clinically mimic mitral
stenosis like the following:
• Left atrial myxoma — is a pedunculated mass arising
from the atrial septum. These patients have prominent
constitutional symptoms like fever and weight loss.
The clinical findings may exhibit postural variation.
• The congenital anomaly of cor-triatriatum consists
of an additional atrial chamber receiving the
pulmonary veins, and this chamber is separated from
the true left atrium by a perforated membrane.
10. What is the natural history of mitral stenosis?
In mitral stenosis, as the mitral valve obstruction
progresses, the left atrial and pulmonary venous pressures
increase. The initial symptoms of mitral stenosis are
secondary to pulmonary venous hypertension. The
increase in pulmonary venous pressure causes fluid
to be driven out of the pulmonary capillaries into the
interstitial spaces. Much of this transudated fluid is
removed by the pulmonary lymphatics. However, some
residual fluid remains, and this causes thickening and
eventually fibrosis of the alveolar walls. This causes
decreased compliance of the lungs and leads to increased
work of breathing producing dyspnea, which is initially
exertional (mitral valve area at this point is 1.4 to
2.5 sq cms).
The alveolar fibrosis causes hypoventilation of the
affected areas of the lung and this results in hypoxemia
of these areas. This hypoxemia is sensed by the
chemoreceptors in the pulmonary veins, leading onto
pulmonary arterial vasoconstriction and pulmonary
artery hypertension. The prime burden of this reactive
pulmonary hypertension is borne by the right ventricle,
leading initially to right ventricular hypertrophy.