Mitral Stenosis
75 MITRAL STENOSIS
David A. Fullerton M.D., Glenn J.R. Whitman M.D.
1. What causes mitral stenosis?
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Rheumatic fever.
2. Which gender most commonly gets mitral stenosis?
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Women by a ratio of 3:2.
3. What are the physical findings of mitral stenosis?
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On ascultation, an opening snap and a diastolic murmer are heard best at the apex.
4. How is the diagnosis confirmed?
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By echocardiography, preferably transesophageal echocardiography (TEE).
5. What is the Gorlin formula?
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A formula used to calculate the area of a heart valve. In simplified terms:
6. What is the normal size of the mitral valve?
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* The normal cross-sectional area is 4-6 cm2.
* Mild mitral stenosis is < 2 cm2.
* Severe mitral stenosis is < 1 cm2.
7. What is the pathophysiology of mitral stenosis?
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Increased left atrial pressure is necessary to push blood through a stenotic mitral valve from the left atrium into the left ventricle. Increased left atrial pressure is transmitted retrograde into the pulmonary veins and pulmonary capillaries and ultimately into the pulmonary arteries. It gives the patient a sensation of dyspnea. A left atrial pressure of approximately 25 mmHg increases pulmonary capillary pressure enough to produce pulmonary edema.
Example: To maintain adequate left ventricular filling across a 1.5-cm2 valve, a pressure gradient of 20 mmHg is required. With a normal left ventricular end-diastolic pressure of 5 mmHg, a 20-mmHg gradient produces a left atrial pressure of 25 mmHg. Left atrial pressure rises even further as flow across the valve increases (increased cardiac output). This high left atrial pressure backs up and floods the lungs (pulmonary edema).
8. What is the main symptom of mitral stenosis?
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Dyspnea on exertion (DOE).
9. What hemodynamic conditions precipitate symptoms in patients with mitral stenosis?
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Tachycardia: Because blood flows through the mitral valve during diastole, a shorter diastole (tachycardia) means less time for blood to move through the stenotic mitral valve, which decreases stroke volume.
Loss of atrial kick: As left atrial pressure increases, the left atrium stretches bigger and the normally organized atrial impulse becomes chaotic (i.e., atrial fibrillation). Increased pressure is required to move blood through the stenotic valve. Loss of presystolic atrial contraction may decrease left ventricular filling by as much as 30%.
10. What complications may result from mitral stenosis?
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1. Hemoptysis from severe pulmonary venous congestion
2. Thromboembolism in patients in atrial fibrillation
3. Endocarditis
4. Pulmonary hypertension and right heart failure
KEY POINTS: MITRAL STENOSIS
1. Mitral stenosis is caused by rheumatic fever.
2. Physical findings include auscultation of an opening snap and a diastolic murmur, heard best at the apex.
3. Mitral commissurotomy and mitral valve replacement are the two operations that may be done for mitral valve stenosis.
11. Why does mitral stenosis cause pulmonary hypertension?
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* Retrograde transmission of increased left atrial pressure
* Reflex pulmonary vasoconstriction initiated by left atrial distention
* Hypertrophy of the pulmonary arteries, leading to remodeling of the pulmonary vasculature
12. What is the medical therapy of mitral stenosis?
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* Beta blockers slow the ventricular rate to about 60 bpm.
* Digoxin slows the ventricular rate (by slowing atrioventricular nodal conduction) in patients with atrial fibrillation.
* Diuretics (furosemide) relieves pulmonary edema.
* Warfarin (Coumadin) is used if the patient is in atrial fibrillation.
13. What is the natural history of mitral stenosis?
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The survival with moderate mitral stenosis is approximately 50% at 10 years.
14. What are the indications for mechanical intervention in mitral stenosis? Show answer
* Symptomatic patients with moderate-to-severe mitral stenosis
* Asymptomatic patients with a mitral valve area < 1 cm2
15. What is the procedure of choice for mitral stenosis?
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If the patient has mobile valve leaflets, no calcium in the valve leaflets, and minimal concurrent mitral regurgitation, then balloon valvuloplasty with a catheter may be an option.
16. Which patients may be appropriate candidates for balloon valvuloplasty?
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Again, this can be a tough call, but patients may be candidates if they are without calcification of the mitral annulus or leaflets, have little or no mitral regurgitation, and have little or no fusion of the mitral chordae tendineae.
17. What are the results of balloon valvuloplasty?
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* Mortality rate < 1%.
* Initial success can be as high as 95% in properly selected patients.
* Valve area may increase to 2 cm2.
* < 90% event-free (you and your patient do not want "events") survival at 7 years, again in properly selected patients.
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strong>18. Which operations may be done for mitral stenosis?
Show answer
* Mitral commissurotomy: The mortality rate is < 2%, and recurrence of mitral stenosis is 2% per year.
* Mitral valve replacement: The mortality rate is 6%.
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Abernathy’s Surgical Secrets, Updated Edition (Book w / Student Consult)
Author / s: Harken Alden H., Abernathy Charles, Moore Ernest Eugene
Year: 2004
Pages: 473
Publishers: Elsevier Mosby; 5th Bk & Acc edition
ISBN: 0323034160
