Mitral stenosis (MS) is the narrowing of the heart’s mitral valve such that it cannot open all the way - obstructing blood flow from the left atrium to the left ventricle. The majority (95%) of mitral stenosis cases are caused by rheumatic fever, which is common in developing countries but rare in developed countries. If left untreated, MS can lead to serious complications such as pulmonary hypertension and heart failure.
The narrowing of the mitral valve blocks blood flow into the left ventricle, which causes pressure to increase within the left atrium and a pressure gradient to develop between the left atrium and the left ventricle. The elevated left atrial pressures are then transmitted to the pulmonary vasculature and the right side of the heart, resulting in pulmonary hypertension and congestive heart failure.
A low-pitched, mid-diastolic or presystolic murmur is heard best over the apex with the bell of the stethoscope. Murmur begins with an opening snap, and a loud S1 can be heard when the mitral valve closes.
There are no specific ECG changes for mitral stenosis (MS). However, left atrial enlargement is a common finding in MS and can be demonstrated by prolonged (broad) P waves on the ECG.