Mitral Stenosis

Background

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
  • Stage B – Progressive valve dysfunction
  • Stage C – Severe asymptomatic disease
    (C2 – severe asymptomatic with LV dysfunction)
  • Stage D – Severe symptomatic disease
Stages of MS

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 & Physical

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 is 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

Investigations

  • 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.

  • Chest Xray: Assess for heart failure and evidence of left atrial enlargement

  • Echocardiography: Transthoracic echocardiography is used to confirm severity of mitral stenosis and determine etiology (ie. rheumatic vs non-rheumatic). In addition can look for consequences, such as left atrial enlargement, pulmonary hypertension, and right ventricular size/function. Left ventricle is usually unaffected. Finally echocardiography (TTE +/- TEE) is important to assess for suitability for balloon commissurotomy if rheumatic mitral stenosis.

Mangement

Asymptomatic MS

  • In asymptomatic MS, serial monitoring with echocardiograms are 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 situation).

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 nonrheumatic) as per CCS 2020 Atrial Fibrillation guidelines

Symptomatic severe MS

Medical Management

  • Heart failure management with diuretics as needed
  • Patients with severe MS do not tolerate tachycardia (sinus or AF) given reliance of 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
  • Nonrheumatic 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 multiple co-morbidities thus generally higher risk for surgery
Intervention for Rheumatic MS

Authors

  • Primary Author: Dr. Atul Jaidka (MD, FRCPC, Cardiology Fellow)
  • Reviewer: Dr. Pavel Antiperovitch (MD, FRCPC Cardiologist)
  • Last Updated: Sept 4, 2021
  • Comments or questions please email feedback@cardioguide.ca