Mitral Stenosis

Abbreviations

Causes

Majority of cases worldwide are due to rheumatic heart disease (most commonly affects the mitral valve)
In high-income countries calcific mitral stenosis is increasingly more common

Stages of Valve Disease

Stage A – Risk factors present
Stage B – Progressive valve dysfunction
Stage C – Severe asymptomatic disease
- C2 – severe asymptomatic disease with LV dysfunction
Stage D – Severe symptomatic disease

Hemodynamics

Patients with mitral stenosis have an obstruction of flow from the left atrium to the left ventricle.
This generates high atrial pressures, which can cause pulmonary edema, pulmonary hypertension, and eventually right sided heart failure.
The natural history of MS is “disease of plateaus”. Patients generally do well, but have periods where their symptoms are worse.
NOTE: Unlike aortic stenosis, aortic regurgitation, and mitral regurgitation, clinicians can wait before intervening on severe MS since waiting does not have any permanent hemodynamic effects on the LV.

History

Patients generally present with shortness of breath on exertion and decreased exercise tolerance
Less commonly they may have hemoptysis (elevated pulmonary pressure), palpitations (atrial fibrillation), fatigue, or stroke (thromboembolism from atrial fibrillation)

Physical exam

Cardiac exam:
- Palpation: RV heave may be present with pulmonary hypertension
- Heart Sounds: loud S1 that becomes softer as stenosis becomes worse, loud P2 (pulmonary hypertension), and progressively single S2
- Opening snap heard at the apex after S2
- Diastolic murmur best heard at the apex
Volume: crackles may be present if there is pulmonary edema and in advanced disease, right heart failure may be present

ECG: Most important feature to assess for is presence of atrial fibrillation. Left atrial enlargement (p wave >0.12s in lead II) or p-mitrale may be present. P-mitrale is a bifid P-wave (M-shaped) in Lead II suggesting left atrial enlargement in mitral stenosis.
Chest X-Ray: Assess for heart failure and evidence of left atrial enlargement
Echocardiography:
- Transthoracic echocardiography is used to confirm severity of mitral stenosis and determine etiology (i.e. rheumatic vs non-rheumatic).
- It can also look for consequences such as left atrial enlargement, pulmonary hypertension, and right ventricular size/function. The left ventricle is usually unaffected.
- Echocardiography (TTE +/- TEE) is important to assess for suitability for balloon commissurotomy if rheumatic mitral stenosis.

In asymptomatic MS, serial monitoring with echocardiograms is indicated. Timing of follow-up interval is based on severity of MS.
Generally safe to wait until symptoms arise (unlike other valvular abnormalities, where symptoms indicate end-stage disease).

Stroke Prevention

Prevention of thromboembolism is very important as high rate of atrial fibrillation
If patient has severe MS, anticoagulation is recommended if:
1. Atrial fibrillation
2. History of embolism (even without atrial fibrillation)
3. Left atrial thrombus
Warfarin is first line for patients with moderate-severe mitral stenosis (rheumatic or non-rheumatic) as per CCS 2020 Atrial Fibrillation guidelines

Medical Management

Heart failure management with diuretics as needed
Patients with severe MS do not tolerate tachycardia (sinus or AF) given reliance on diastolic filling time for preload, thus heart rate control is important

Valve Intervention

Rheumatic Mitral Stenosis Indications for Intervention
- Severe MS + symptoms (Class 1)
- Severe MS + pulmonary hypertension or new AF (Class 2)
- Percutaneous balloon valvotomy is preferred if valve anatomy is favourable (less than moderate MR)
  - Otherwise should go for mitral valve surgery
Non-rheumatic Calcific Mitral Stenosis
- No Class 1 indication for surgery
- If severe MS and severely symptomatic, should have a risk benefit discussion with patients
  - Patients with calcific MS are often older and have multiple co-morbidities, thus are generally higher risk for surgery