Mitral valve stenosis sometimes called mitral stenosis is a narrowing of the heart’s mitral valve. This abnormal valve doesn’t open properly, blocking blood flow into the main pumping chamber of your heart (left ventricle). Mitral valve stenosis can make you tired and short of breath, among other problems.
What causes mitral valve stenosis?
Mitral stenosis can be caused by congenital heart defects, mitral valve prolapse, rheumatic fever, lupus and other conditions. Rheumatic fever is a childhood illness that sometimes occurs after untreated strep throat or scarlet fever.
Rheumatic fever is rare in high-income countries such as the United States but remains a concern in some low- and middle-income nations. Rheumatic fever can damage the heart valves leading to rheumatic heart disease. Mitral stenosis resulting from RHD is called rheumatic mitral stenosis. Although most mitral stenosis is caused by RHD, it can also result from a calcium build up on the heart valves. This is more common in older patients and is called calcific mitral stenosis.
Symptoms and Signs
Two clinical syndromes classically occur in patients with mitral stenosis. In mild to moderate mitral stenosis, LA pressure and cardiac output may be essentially normal, and the patient is either asymptomatic or symptomatic only with extreme exertion. The measured valve area is usually between 1.5 cm2 and 1.0 cm2. In severe mitral stenosis (valve area less than 1.0 cm2), severe pulmonary hypertension develops due to a “secondary stenosis” of the pulmonary vasculature. In this condition, pulmonary edema is uncommon, but symptoms of low cardiac output and right heart failure predominate.
A characteristic finding of rheumatic mitral stenosis is an opening snap following A2 due to the stiff mitral valve.
The interval between the opening snap and aortic closure sound is long when the LA pressure is low, but shortens as the LA pressure rises and approaches the aortic diastolic pressure. As mitral stenosis worsens, there is a localized low-pitched diastolic murmur whose duration increases with the severity of the stenosis when the mitral gradient continues throughout more of diastole. The diastolic murmur is best heard at the apex with the patient in the left lateral position.
Mitral regurgitation may be present as well.
Paroxysmal or chronic atrial fibrillation eventually develops in 50–80% of patients. Any increase in the heart rate reduces diastolic filling time and increases the mitral gradient. A sudden increase in heart rate may precipitate pulmonary edema. Therefore, heart rate control is important, with slow heart rates allowing for more diastolic filling of the LV.
Echocardiography is the most valuable technique for assessing mitral stenosis (Table 10–1). LA size can also be determined by echocardiography; increased size denotes an increased likelihood of atrial fibrillation and thrombus formation.
Because echocardiography and careful symptom evaluation provide most of the needed information, cardiac catheterization is used primarily to detect associated coronary or myocardial disease—usually after the decision to intervene has been made.
Although medications can’t fix a valve defect, they can help with symptoms. Your health care team may prescribe diuretics to reduce fluid accumulation in the lungs, blood thinners* to prevent clots from forming, or drugs to control the heart rhythm if those are indicated. The mitral valve can usually be repaired or replaced with surgery, or a minimally invasive procedure. The choice of procedure is based on many factors including the cause of the mitral stenosis (rheumatic or calcific), condition of the valve, risk of surgery, severity of symptoms, heart function, and availability of procedures.
Mitral Valve Commissurotomy
For rheumatic mitral stenosis, a commissurotomy may be performed. During this procedure the valve leaflets that have become fused together are separated. This can be done using a balloon (percutaneous mitral balloon commissurotomy or PMBC) or surgery. In both cases, once the leaflets have been separated, the valve opening is increased and blood flow through the valve is improved. In more advanced rheumatic mitral valve stenosis, surgical repair or replacement of the mitral valve may be required.