Early Percutaneous Mitral Intervention in Asymptomatic Moderate Mitral Stenosis
Condition: Moderate Mitral Stenosis
MeSH terms: Mitral Valve Stenosis; Constriction, Pathologic
Study type: Interventional

Summary: 
      Although percutaneous mitral commissurotomy (PMC) has been accepted as an effective treatment
      for symptomatic patients with moderate or severe mitral stenosis (MS), most asymptomatic
      patients are not candidates for PMC owing to the small but inherent procedure-related risks.
      Asymptomatic patients with MS show good survival rates up to 10 years, but there was a sudden
      deterioration precipitated by atrial fibrillation or embolism in half of the patients.
      Because the success rates of PMC were improved to more than 95% in ideal patients from highly
      selected centers and early PMC may decrease the occurrence of adverse events, such as atrial
      fibrillation or embolism, experienced centers tend to perform PMC at an early stage of
      disease. However, the potential benefits of early preemptive PMC in asymptomatic patients
      should be balanced against the real risks related to the procedure, and further studies of
      the efficacy of PMC in the prevention of embolism are necessary to extend its indications to
      asymptomatic patients. To the best of our knowledge, No randomized trials have been performed
      to ascertain the optimal timing of intervention in asymptomatic patients with significant MS.
      The early percutaneous MITral Intervention versus conventional manaGement in Asymptomatic
      moderate miTral stEnosis (MITIGATE) trial was designed to compare clinical outcomes of early
      intervention with those of a conventional management based on current guidelines in
      asymptomatic moderate mitral stenosis.
    

Detailed description: 
      We enroll consecutive asymptomatic patients with moderate mitral stenosis who are candidates
      for both early percutaneous mitral commissurotomy (PMC) and conventional treatment at 3
      centers in Seoul, Korea.

      Echocardiographic evaluation is performed before enrollment, immediately after PMC and
      annually during follow-up. All patients undergo two-dimensional echocardiography and/or
      transesophageal echocardiography to detect left atrial thrombi. Morphologic features of the
      mitral valve (MV) are categorized as described previously (14), and total echocardiographic
      score is obtained by adding the scores for leaflet mobility, thickness, calcification, and
      subvalvular lesions. The MVA is measured by direct planimetry of the mitral orifice, and MS
      severity is graded as mild, moderate, or severe when MVA was > 1.5, 1.0 to 1.5, or < 1.0 cm2,
      respectively. The severity of mitral and tricuspid regurgitation is assessed
      semiquantitatively or using quantitative methods and classified as mild, moderate, or severe.
      Pulmonary artery systolic pressure (PAP) is estimated by continuous wave Doppler with the
      simplified Bernoulli equation.

      All study patients regularly visit their attending physicians at 3 monthly interval for
      maintenance of anticoagulation therapy or every year for annual re-evaluation. Patients in
      the conventional treatment group who become symptomatic during follow-up are referred for PMC
      or mitral valve surgery. An embolic event is defined as a systemic embolism fulfilling both
      prespecified criteria: acute onset of clinical symptoms or signs of embolism and occurrence
      of new lesions confirmed by imaging studies. A specific diagnosis of cerebral infarction is
      confirmed by an experienced neurologist and additional brain magnetic resonance imaging is
      performed if indicated.

      We estimate that a sample size of 166 patients would provide 80% power to detect a
      significant difference with respect to the primary end point at the 2-sided significance
      level of 0.05, assuming 3-year event rates of 13% in the conventional treatment group and 2%
      in the early PMC group, and drop-out rate of 5%. These rates are based on the results of our
      previous study. Analyses are performed on an intention-to-treat basis. To analyze primary
      outcome, estimates of cumulative event rates are calculated by the Kaplan-Meier method and
      compared employing the log-rank test. For Kaplan-Meier analysis, we analyze all clinical
      events by time to first event. Hazard ratios with 95% confidence intervals are derived with
      the use of the Cox proportional hazards model.
    

Intervention name(s): Percutaneous Mitral Commissurotomy
Intervention type(s): Procedure
Intervention description(s): Percutaneous mitral commissurotomy is performed by experienced interventional cardiologists using the Inoue balloon technique. During the procedure, conventional hemodynamic parameters are monitored. A successful immediate result is defined as a mitral valve area > 1.5 square cm with less than moderate to severe mitral regurgitation.
Other intervention name(s): Percutaneous mitral valvuloplasty
Allocation: Randomized
Intervention model: Parallel Assignment
Intervention model description: early percutaneous mitral commissurotomy
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: Mitral Stenosis; Mitral Valvuloplasty