Moderate Mitral Stenosis Clinical Trial
Official title:
Early Percutaneous Mitral Intervention Versus Conventional Management in Asymptomatic Moderate Mitral Stenosis
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.
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.
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