Cardiovascular · Topic 32 of 48

Mitral Stenosis

Cardiovascular · valvular heart disease

Mitral Stenosis

A narrowed rheumatic mitral valve: slow the heart so the atrium can empty, anticoagulate atrial fibrillation with warfarin, and open the valve with a balloon.

Key numbers

Severe MS: valve area ≤ 1.5 cm²MVA ≤ 1.5 cm²

Consider intervening: PASP > 50 or new AFPASP > 50 mmHg

01 · Defined bySevere MS: valve area ≤ 1.5 cm²

Echocardiography grades mitral stenosis: normal valve area is 4–5 cm²; moderate is > 1.5–2.5 cm²; severe is ≤ 1.5 cm² (or diastolic pressure half-time ≥ 150 ms), when symptoms are often present.

02 · WhyTachycardia or AF causes pulmonary edema

Tachycardia shortens diastole and atrial fibrillation removes the atrial kick, so left atrial pressure rises and pulmonary edema follows; give a diuretic and a beta-blocker or nondihydropyridine calcium channel blocker to slow the rate.

03 · GiveRheumatic MS with AF: warfarin

Anticoagulate rheumatic mitral stenosis with atrial fibrillation (current or prior), prior embolism or left atrial thrombus with a vitamin K antagonist (warfarin); DOACs are not indicated — rivaroxaban was inferior to VKA in INVICTUS.

Causes & risk factors

Why it happens

Rheumatic fever is the usual causeRheumatic fever causes most mitral stenosis (commissural fusion, thickened chordae), often without a remembered episode; in older patients mitral annular calcification is a common cause. About 80% of patients are women.

Presentation

What you'll see

Opening snap, then low diastolic rumble at apex must knowMitral stenosis gives a loud S1, an early diastolic opening snap and a low-pitched rumbling diastolic murmur heard best at the apex with the bell, patient in left lateral decubitus.

Pregnancy or AF unmasks silent MSMany patients stay asymptomatic until pregnancy (higher blood volume) or atrial fibrillation; symptoms are those of heart failure — exertional dyspnea, orthopnea, PND — plus hemoptysis or an embolic stroke as the first event.

Shorter S2–opening snap interval means more severeAs stenosis worsens and left atrial pressure rises, the opening snap moves closer to S2 and the murmur lengthens; a calcified, immobile valve may lose the snap and loud S1.

ECG and CXR show left atrial enlargementECG: left atrial enlargement (broad notched P in II, deep terminal negative P in V1). Chest x-ray: straightened left heart border, double density along the right heart border, Kerley B lines.

Do right now

In this order

First moves

Tachycardia or AF causes pulmonary edema

→

Rheumatic MS with AF: warfarin

→

Balloon commissurotomy for severe symptomatic MS

Why each step

Tachycardia or AF causes pulmonary edemaTachycardia shortens diastole and atrial fibrillation removes the atrial kick, so left atrial pressure rises and pulmonary edema follows; give a diuretic and a beta-blocker or nondihydropyridine calcium channel blocker to slow the rate.

Rheumatic MS with AF: warfarinAnticoagulate rheumatic mitral stenosis with atrial fibrillation (current or prior), prior embolism or left atrial thrombus with a vitamin K antagonist (warfarin); DOACs are not indicated — rivaroxaban was inferior to VKA in INVICTUS.

Balloon commissurotomy for severe symptomatic MSPercutaneous mitral balloon commissurotomy is the procedure of choice for severe symptomatic mitral stenosis with a favorable valve; outcomes match surgery.

Management

Orders

Surgery when the valve is unsuitableSurgical commissurotomy or mitral valve replacement is reserved for severely symptomatic patients whose valve is unsuitable for balloon commissurotomy, who need other cardiac surgery, or who lack access to the percutaneous procedure.

Consider intervening: PASP > 50 or new AFIn asymptomatic severe mitral stenosis with a suitable valve, balloon commissurotomy may be considered when pulmonary artery systolic pressure exceeds 50 mmHg or new atrial fibrillation develops.

Red flags & don'ts

Avoid harm

TEE to exclude left atrial thrombus first avoidBalloon commissurotomy is avoided with left atrial thrombus, moderate–severe mitral regurgitation, heavy commissural calcification or subvalvular distortion; transesophageal echo detects left atrial appendage thrombus that transthoracic echo misses.

Pulmonary hypertension leads to right heart failure complicationChronic left atrial hypertension causes secondary pulmonary hypertension (loud P2, RV heave), then right ventricular failure with tricuspid and pulmonary regurgitation.

Teach & follow up

Patient education

Rheumatic fever prophylaxis, not endocarditis prophylaxisNative mitral stenosis needs prophylaxis against rheumatic fever recurrence where appropriate; endocarditis antibiotic prophylaxis is not recommended unless the valve has been replaced.

More detail

Reference

Show 7 reference facts

Anticoagulation may also be considered with dense spontaneous echo contrast or a left atrium > 50 mm, though this is unstudied.

Untreated atrial fibrillation with mitral stenosis carries up to about a 5% annual stroke risk.

Moderate mitral stenosis with symptoms and an exercise mean gradient > 15 mmHg or pulmonary capillary wedge pressure > 25 mmHg may be considered for balloon commissurotomy.

Calcific (annular) mitral stenosis has no commissural fusion, so balloon commissurotomy does not help; intervention is delayed until symptoms are severe, and transcatheter valve-in-MAC is an option for poor surgical candidates.

After mitral valve replacement, a mechanical valve needs lifelong warfarin; a bioprosthetic mitral valve needs warfarin for 3–6 months postoperatively.

Less common findings: hoarseness from left recurrent laryngeal nerve compression by the dilated left atrium (Ortner syndrome) and a malar flush when cardiac output is low.

Balloon commissurotomy complications include new mitral regurgitation, embolism and tamponade; the transseptal atrial septal defect usually closes spontaneously.

Pearl

In mitral stenosis, diastole is the only time the left ventricle fills — protect it by keeping the heart rate slow.

Sources · Merck Manual Professional — Mitral Stenosis (full review Jun 2025) · Merck Manual Professional — Overview of Cardiac Valvular Disorders (anticoagulation for native valve disease) · Connolly SJ et al. Rivaroxaban in Rheumatic Heart Disease-Associated Atrial Fibrillation (INVICTUS). N Engl J Med 2022 · Starter sheet built from the verified AGACNP fact map (facts reviewed 2026-10-15).