Long-Term Results of the Melody Valve in the Left Atrioventricular Valve Position in Very Young Children

<b>Background:</b> Mitral valve replacement in infants is highly challenging due to size limitations and the lack of suitable prosthetic valves. The Melody™ valve, originally developed for transcatheter pulmonary valve replacement, offers an off-label alternative for surgical implantation in the mitral position, with the possibility of balloon expansion and valve-in-valve procedures during somatic growth. <b>Aim:</b> To evaluate the long-term outcomes and technical feasibility of the Melody™ valve in the mitral position in infants and very young children following failed surgical repair. <b>Methods:</b> This single-center, retrospective observational study included four pediatric patients who underwent Melody™ valve implantation in the mitral position between October 2015 and February 2020. Data on patient characteristics, surgical techniques, perioperative management, complications, and long-term outcomes were collected and analyzed through April 2024. All patients were followed clinically and with echocardiography. Additional interventions, including balloon dilations and valve-in-valve procedures, were documented. <b>Results:</b> All patients (mean age: 7 months; mean weight: 6.8 kg) had undergone prior mitral valve repair and presented with severe mitral dysfunction. Melody™ valves were successfully implanted with no perioperative mortality. Over a mean follow-up of 5.9 years (range: 4.2-8.5), six balloon dilations were performed (1-2 per patient), and one valve-in-valve procedure was conducted due to progressive stenosis. Two patients required valve excision: one for endocarditis, one for degeneration. The mean valve longevity before replacement was 44.6 months. Three patients developed complete atrioventricular block requiring pacemaker implantation. No thromboembolic events or LVOT obstructions were noted. Mean transmitral gradients at final follow-up were <5 mmHg in all patients. <b>Conclusion:</b> The Melody™ valve provides an adaptable solution for mitral valve replacement in infants, allowing for staged expansion and valve-in-valve strategies. Despite a notable risk of AV block, the long-term outcomes are promising, especially in patients too small for conventional prostheses. Close follow-up and further multicenter studies are needed to optimize patient selection and long-term management.