Pathophysiology

• Increased transvalvular flow or decreased diastolic filling time may lead to worsening symptoms of MS. This occurs with pregnancy, exercise, hyperthyroidism, atrial fibrillation (AF) with rapid ventricular response, and fever.
• MS causes increased pressure in the LA, which then dilates as a compensatory mechanism. This causes the LA to dilate and fibrose, which then leads to atrial arrhythmias and thrombus formation.
• A sustained increase in pulmonary venous pressures is transmitted backward to cause pulmonary hypertension (PH) and with time, increased pulmonary vascular resistance and right ventricular pressure overload and dysfunction.

History

After a prolonged asymptomatic period, patients may report any of the following: dyspnea, decreased functional capacity, orthopnea, paroxysmal nocturnal dyspnea, fatigue, palpitations, systemic embolism, hemoptysis, chest pain.

Physical Examination

• Opening snap (OS) caused by sudden tensing of the valve leaflets; the A₂-OS interval varies inversely with the severity of stenosis (shorter interval = more severe stenosis).
• Mid-diastolic rumble: low-pitched murmur heard best at the apex with the bell of the stethoscope; the severity of stenosis is related to the duration of the murmur, not intensity.
• Signs of right-sided heart failure and PH.

Diagnostic Testing

• ECG: left atrial enlargement (LAE), AF, right ventricular hypertrophy.
• CXR: enlarged chambers, calcification of the mitral valve and/or annulus.
• TTE
  • Assess valve leaflets and subvalvular apparatus.
  • Determine mitral valve area (MVA) and mean transmitral gradient (severe considered MVA ≤1.5 cm² or mean transmitral gradient of >5–10 mm Hg).
  • Estimate pulmonary artery systolic pressure (PASP) and evaluate right ventricular size and function.
• Transesophageal echocardiogram (TEE): Imaging modality of choice for evaluation of anatomy and functional significance. Also used to rule out left atrial thrombus.
• Exercise stress testing: indicated when symptoms are out of proportion to severity indicated by TTE.
• Cardiac catheterization: Rarely used. Useful in cases of discordant or inconclusive data by echocardiography. May provide clarification to the etiology of severe PH when out of proportion of the severity of MS. Typically performed in patients going for mitral valve replacement with risk factors for CAD.

Medical Management

• Diuretics, β-blockers, and low-salt diet for heart failure symptoms.
• AF occurs in 30%–40% of patients with severe MS.
  • Therapy is mostly aimed at rate control and prevention of thromboembolism.
  • Class I indication for anticoagulation for prevention of systemic embolization in patients with MS regardless of CHADS2VASC score.¹

Percutaneous Mitral Balloon Commissurotomy

• Balloon inflation separates the leaflets, yielding an increased valve area.
• Indicated only in rheumatic MS where there is thickening of the leaflets and annulus is mostly spared.
• Procedure of choice in experienced centers in patients without contraindications (such as moderate or severe MR and left atrial appendage thrombus).
• Recommendations for percutaneous mitral balloon commissurotomy¹
  • Symptomatic patients with severe MS (valve area ≤1.5 cm²) (stage D) and favorable valve anatomy in the absence of contraindications (i.e., LA clot or moderate to severe MR) (Class I)
  • Other indications: Asymptomatic patients with severe MS and pulmonary hypertension (PASP >50 mm Hg) or new onset AF (Class II)

Surgical Management

Recommendations for mitral valve surgery¹: Severely symptomatic patients with severe MS who are not candidates for or failed previous percutaneous mitral balloon commissurotomy, or who are undergoing other cardiac procedures (Class I).