RESUMO
BACKGROUND: We evaluated the range of prosthetic size-to-weight ratio to optimize valve survival in small children. METHODS: A single-institution retrospective review of mechanical mitral valve replacements from 1995 to 2019 was performed. Prosthetic valve size-to-weight ratio was calculated as the prosthetic valve diameter divided by the patient's operative weight in children less than or equal to 35 kg. Patient death or reoperation on the valve was analyzed by size-to-weight ratio. Identifying a U-shaped distribution of events, patients were stratified as being in the nadir of the distribution or on the edges. RESULTS: Mechanical mitral valve replacements were performed in 56 (75%) children weighing less than or equal to 35 kg. Median follow-up time was 3.7 (interquartile range, 0.46-12) years. Median size-to-weight ratio was 1.5 (interquartile range, 1.0-2.0). A second replacement was required in 15 (27%) patients. Death occurred in 6 (11%) patients, including 3 after reoperation. The nadir of U-shaped distribution of events by size-to-weight ratio was bounded by a ratio from 1 to 2, which included 29 (52%) patients. A size-to-weight ratio from 1 to 2 provided optimal outcomes regardless of patient age. Reoperation-free survival at 5 years was 96% for patients with a ratio from 1 to 2 and 46% for patients with a ratio less than 1 or greater than 2. Patients with size-to-weight ratio 1 to 2 had longer reoperation-free survival than patients with a ratio less than 1 or greater than 2 (P < .001). CONCLUSIONS: Regardless of patient age, in patients less than or equal to 35 kg, optimal reoperation-free survival after prosthetic mitral valve replacement can be obtained by placing a prosthetic valve whose diameter is between 1 and 2 times the patient's weight in kilograms.