Rheumatic heart disease is the most important cause of mitral stenosis. Other causes of mitral stenosis like congenital mitral stenosis due to parachute mitral valve are extremely uncommon. So for practical purposes, mitral stenosis can be taken to be of rheumatic etiology, especially in a developing country.

Normal mitral valve area is about 5 sq cm. When the area falls below 2 sq cm it is considered as mitral stenosis. The commonest cause of mitral stenosis is as sequelae of rheumatic carditis.

Grading of severity of mitral stenosis by valve area

Mild mitral stenosis: Mitral valve area 1.5 – 2.0 sq cm

Moderate mitral stenosis: Mitral valve area 1.0 – 1.5 sq cm

Severe mitral stenosis: Mitral valve area <1.0 sq cm

Symptoms of mitral stenosis

The predominant symptom of mitral stenosis is exertional dyspnoea. Paroxysmal nocturnal dyspnea is a classical symptom of mitral stenosis which tends to occur earlier in the natural history and may disappear later on. Palpitation can occur due to arrhythmias in mitral stenosis. A patient with severe mitral stenosis may also present with acute pulmonary edema, usually in the presence of an intercurrent infection or arrhythmia. Rarely a patient may present with an embolic episode as the first manifestation of mitral stenosis. Embolisation secondary to left atrial thrombi is more occur with associated atrial fibrillation in mitral stenosis.

Juvenile mitral stenosis

The term juvenile mitral stenosis was coined by Prof. SB. Roy for patients with onset of symptoms of mitral stenosis before the age of 20 years. It is more common in the developing countries and the relatively underprivileged regions of developed countries. More frequent and sever rheumatic activity is thought to be the reason of earlier onset of features of mitral stenosis. They tend to have a more rapid course marked by severe pulmonary hypertension and a higher chance for restenosis after successful mitral valvotomy.