BACKGROUND: Durability assessment of mitral valve repair for degenerative valve incompetence is actually limited to reoperation as the primary indicator, with valve-related risk factors for late death as a secondary indicator. We assessed serial echocardiographic follow-up of valve function as an indicator of the durability of mitral valve repair. METHODS AND RESULTS: In 242 patients who had undergone mitral valve repair for degenerative valve incompetence, echocardiographic follow-up of valve function, rate of reoperation, survival, and clinical outcome was studied. At 8 years after repair, clinical outcome was excellent, survival was 90.9+/-3.2%, freedom from reoperation was 94.2+/-2.3%, and freedom from anticoagulation bleeding and thromboembolic events was 90.4+/-2.7%. However, freedom from non-trivial mitral regurgitation (>1/4) was 94.3+/-1.6% at 1 month, 58.6+/-4.9% at 5 years, and 27.2+/-8.6% at 7 years. Freedom from severe mitral regurgitation (>2/4) was 98.3+/-0.9% at 1 month, 82.8+/-3.8% at 5 years and 71.1+/-7.4% at 7 years. The linearized recurrence rate of non-trivial mitral regurgitation (>1/4) was 8.3% per year and of severe mitral regurgitation (>2/4) was 3.7% per year. Inadequate surgical techniques (chordal shortening, no use of annuloplasty ring or sliding plasty) could only partially explain recurrence of regurgitation. In selected patients who did not have these risk factors, linearized recurrence rates were 6.9% per year and 2.5% per year, respectively. CONCLUSIONS: The durability of a successful mitral reconstruction for degenerative mitral valve disease is not constant, and this should be taken into account when asymptomatic patients are offered early mitral valve repair.