Mitral Annular Growth in Children Following Early Mechanical Mitral Valve Replacement

Irreparable mitral pathology may lead to early mitral valve replacement (MVR) in children. Often, a small mechanical prosthesis (<23 mm) is required, raising concerns about annular growth in patients who may eventually require subsequent mitral valve re-replacement (MVRR). The aim of this study was to evaluate interval mitral annular growth in this cohort. Between January 1972 and December 2006, 164 children underwent MVR with a mechanical prosthesis; 110 of these children (median age, 4 years; range, 7 days to 14 years) received a small mechanical prosthesis (<23 mm). The most common diagnoses were congenital mitral stenosis (10%), regurgitation (46%), and left atrioventricular valve dysfunction after previous atrioventricular septal defect repair (44%). The cohort was analyzed for age, body surface area (BSA), prosthesis size, and Z score at the time of MVR and MVRR. At the time of MVR, 78 patients had a BSA of 0.77 ± 0.06 m², had an annular size of 24 ± 0.62 mm (Z score, 2.91 ± 0.23), and ultimately did not require MVRR. Another cohort, who eventually did require MVRR (n = 24), had an initial BSA at the time of MVR of 0.62 ± 0.05 m² (P = NS vs MVR only) and an annular size of 20 ± 0.49 mm (Z score, 1.85 ± 0.22) (P = .008 vs MVR only). In the interval between MVR and MVRR (7.8 ± 1.1 years), BSA increased to 1.12 ± 0.07 m², and annulus size increased to 24 ± 0.47 mm (Z score, 1.80 ± 0.28). These data suggest growth of the mitral annulus following MVR with a small mechanical prosthesis, as evidenced by an unchanged Z score in the setting of normal interval increase in BSA. Additionally, there was a statistically significant difference in initial Z scores between the cohorts requiring MVRR and those who have not needed re-replacement, suggesting that the feasibility of placement of a slightly larger prosthesis may be associated with a decreased need for MVRR.