Mitral stenosis overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-In-Chief: Mohammed A. Sbeih, M.D. [2]
Overview
Mitral stenosis is a valvular heart disease characterized by narrowing of the orifice of the mitral valve of the heart.[1] In normal cardiac physiology, the mitral valve opens during left ventricular diastole, to allow blood to flow from the left atrium to the left ventricle. Blood flows in the proper direction because during this phase of the cardiac cycle; the pressure in the left ventricle is lower than the pressure in the left atrium, and the blood flows down the pressure gradient. In the case of mitral stenosis, the valve does not open completely, and to transport the same amount of blood, the left atrium needs a higher pressure than normal to overcome the increased gradient. Mitral stenosis typically progresses slowly (over decades) from the initial signs of mitral stenosis to NYHA functional class II symptoms to the development of atrial fibrillation to the development of NYHA functional class III or IV symptoms. Once an individual develops NYHA class III or IV symptoms, the progression of the disease accelerates and the patient's condition deteriorates. Severe mitral stenosis (MS) is eventually lethal disease unless treated with vulvotomy or valve replacement, it may progress to serious complications like pulmonary hypertension, heart failure and death. Most of the cases are due to rheumatic heart disease.
Pathophysiology
Mitral stenosis (MS) is most commonly secondary to acute rheumatic fever. Generally, the initial valvulitis is associated with valvular regurgitation but over a period of 2 or more years, the commissures fuse and the valves thicken and calcify. The chordal supporting structure also calcifies and retracts. The result is the typical “fish mouth deformity”. 70% of the time; the mitral valve is involved in isolation, and 25% of the time; the aortic valve is involved as well. The tricuspid and pulmonic valves are involved less commonly. Patients develop symptoms when the mitral vavle area is 2 to 2.5 cm2.
Causes
The majority of cases of mitral stenosis result from rheumatic heart disease, which occurs as a complication of group A streptococcal infection in genetically susceptible individuals. Some cases may be congenital.
Epidemiology and Demographics
In developed countries, the prevalence of mitral stenosis continues to decline as the prevalence of rheumatic fever declines. Currently, the estimated incidence in the United States is 1:100,000. The incidence in higher in developing countries.
Natural History, Complications and Prognosis
After the initial episode of rheumatic fever, there is a latent period of 20 years before the onset of symptoms in mitral stenosis. Complications of mitral stenosis are left and right heart failure, endocarditis and embolization (stroke) and pulmonary embolism. Survival in asymptomatic patients is 80% at 10 years. Once symptoms develop, if mitral stenosis is left untreated, survival at 10 years is only 15%. The majority of patients die due to complications of pulmonary hypertension (which is associated with a mean survival of 3 years after its onset) and right heart failure.
Diagnosis
History and Symptoms
After the initial episode of rheumatic fever, there is an approximate 20 year latent period before symptoms develop in mitral stenosis. Approximately half the patients will not have a recollection of having rheumatic fever. In the developed world, most patients develop symptoms between the age of 20 and 50. Initial symptoms are worsened by exercise or tachycardia. Symptoms may begin with an episode of atrial fibrillation, or may be triggered by pregnancy or other metabolic stress, such as an infection. The symptoms are initially those of left heart failure, and subsequently are those of right heart failure.
Physical Examination
Mitral stenosis is associated with a rumbling diastolic murmur and an opening snap. Later in the course of the disease there are signs of right heart failure such as pedal edema, ascites, and congestive hepatopathy.
Chest X Ray
Left atrial enlargement is seen on chest x ray in the patient with mitral stenosis.
Echocardiography
In most cases, the diagnosis of mitral stenosis is most easily made by echocardiography, which shows decreased opening of the mitral valve leaflets, and increased blood flow velocity during diastole. The trans-mitral gradient as measured by Doppler echocardiography is the gold standard in the evaluation of the severity of mitral stenosis. Cases of mild mitral stenosis (mitral valve area >1.5 cm2) can be followed up yearly with history, physical examination, EKG and some imaging studies like echocardiography.
Cardiac Catheterization
While echocardiography remains the diagnostic imaging modality of choice, simultaneous left and right heart catheterization demonstrates a pressure gradient such that the pulmonary capillary wedge pressure (a surrogate of the left atrial pressure) exceeds the left ventricular end diastolic pressure.
Medical Therapy
Patients with mitral stenosis who develop atrial fibrillation require anticoagulation and rate control.
References
- ↑ Carabello BA (2005). "Modern management of mitral stenosis". Circulation. 112 (3): 432–7. doi:10.1161/CIRCULATIONAHA.104.532498. PMID 16027271. Unknown parameter
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