The optimal timing of surgical intervention remains controversial in asymptomatic patients with very severe aortic stenosis. The investigators therefore try to compare long-term clinical outcomes of early surgery with those of conventional treatment strategy in a prospective randomized trial.

Management of asymptomatic patients with severe aortic stenosis (AS) remains controversial, and the combined risks of aortic valve surgery and late complications of aortic valve prosthesis need to be balanced against the possibility of preventing sudden death and lowering cardiac mortality. Considering that sudden cardiac death occurs at a rate of approximately 1% per year and that the average postoperative mortality of isolated AV replacement is 3.0-4.0%, the 2007 European Society of Cardiology guidelines do not recommend aortic valve surgery for asymptomatic patients with severe AS and the 2006 American College of Cardiology/American Heart Association guidelines recommend surgery as a class IIb indication only in patients with extremely severe AS and who are at low operative risk. Clinical outcomes vary widely according to the severity of stenosis in asymptomatic AS, and asymptomatic patients with very severe AS are often referred for aortic valve replacement in clinical practice despite the lack of data supporting early surgery. Rosenhek et al recently reported a worse prognosis with a higher event rate and a risk of rapid deterioration in very severe AS, and the investigators also recently reported that compared with the conventional treatment strategy, early surgery in patients with very severe AS is associated with an improved long-term survival in a prospective, observational study. However, there have been no prospective,randomized studies comparing early surgery with a watchful waiting strategy in very severe AS. We sought to compare long-term clinical outcomes of early surgery with those of conventional management based on current guidelines.

Inclusion Criteria:

• asymptomatic patients with very severe aortic stenosis who are potential candidates for early surgery. Very severe aortic stenosis are defined as a critical stenosis in the AV area ≤ 0.75 square centimeter fulfilling one of the following criteria; a peak aortic velocity ≥ 4.5 m/sec or a mean transaortic pressure gradient ≥ 50 mmHg on Doppler echocardiography.

According to the revised 2014 AHA/ACC Valvular Heart Disease Guideline that recommends exercise testing to confirm the absence of symptoms in asymptomatic patients with severe AS (Class IIa), eligible patients with a positive exercise test will be excluded from the entry after May, 2014.

Exclusion Criteria:

• Exertional dyspnea
• Angina
• Syncope
• Left ventricular ejection fraction < 50%
• Significant aortic regurgitation
• Significant mitral valve disease
• Pregnancy
• Age < 20 years or > 80 years
• Coexisting malignancies
• Positive exercise test