Predictors of prosthesis survival, growth, and functional status following mechanical mitral valve replacement in children aged <5 years, a multi-institutional study

Background - Prosthesis survival, growth, and functional status after initial mechanical mitral valve replacement (MVR) in children <5 years of age are poorly defined. Methods and Results - The experience of the Pediatric Cardiac Care Consortium (45 centers, 1982 to 1999), which included 102 survivors after initial MVR, was analyzed. Median follow-up: 6.0 years (interquartile range: 3.0 to 10.6 years; 96% complete). Twenty-nine survivors had undergone a second MVR at an interval of 4.8 ± 3.8 years after initial MVR. Reasons for second MVR were prosthetic valve stenosis 24 (83%), thrombosis 4 (14%), and endocarditis 1 (3%). For those who had second MVR, prosthesis sizes were: first MVR 19±2 mm and second MVR 22±3 mm, and their body weight increased from 7.4±2.8 kg to 16.8±10.5 kg. To identify risk factors for having a second MVR, the 29 second MVR survivors were compared with the 73 who did not have a second MVR on first-MVR demographic and perioperative variables. By univariate analysis, patients with shorter prosthesis survival were younger, weighed less, had smaller prostheses, greater ratio of prosthesis size:body weight, were less likely to have a St. Jude prosthesis and more likely to have Shone's syndrome. By multivariate analysis prosthesis survival was predicted only by first MVR age: odds ratio (OR) 7.7 (95% confidence interval [CI] 2.6-22.7) and prosthesis size: OR 6.8 (95% Cl 2.6-18.2). High risk patients (age <2 years and prosthesis <20 mm at first MVR) had an OR=46.3 compared with low-risk patients (age ≥2 years and prosthesis >20 mm at first MVR) over similar follow-up intervals. Using first-MVR weight-matched controls, body weight increased similarly for patients <2 years old who had a second MVR versus those who did not. Prosthesis size, however, differed significantly, with second MVR patients having smaller prostheses at first MVR (18.7±0.8 mm versus 22.4±3.6 mm, P = 0.017). An estimate of current New York Heart Association (NYHA) functional status was class 1 in 76%, class 2 in 22%, and classes 3 or 4 in 2%. Conclusion - Prosthesis survival can be predicted based on first MVR age and prosthesis size. Somatic growth is comparable regardless of the need for second MVR. There is an increment in prosthesis size at second MVR, suggesting continued annular growth. Significant limitation of function after MVR is uncommon. MVR may be an appropriate strategy for children <5 years old despite the risk of second MVR in the youngest patients in whom the smallest prostheses are used.