Mitral valve disease in children poses a significant challenge due to its high morbidity and postoperative mortality. Even when repair is feasible, the associated mortality and reoperation rates remain substantial, reflecting the imperfect nature of available treatments for a valve that must continue to grow under abnormal physiological and anatomical conditions. When repair is not possible or unsuccessful, mitral valve replacement becomes inevitable. However, mitral valve replacement in children, especially those under 2 years of age, carries a short- and medium-term mortality rate of 20–30%. This raises the question: is the implantation of the Melody prosthesis a viable alternative as a bridge to mechanical valve replacement? 

To address this question, the present study retrospectively analyzed all biventricular circulation patients who underwent Melody prosthesis implantation in the mitral position between 2013 and 2023. This single-center study evaluated survival, durability, and complications of the procedure. Survival analysis was performed using Kaplan–Meier curves, and the Fine and Gray subdistribution method was applied to quantify the cumulative incidence of mechanical prosthesis implantation, reoperation, and length of hospital stay. Surgical decisions, including indications, timing, and type of replacement, were made during multidisciplinary meetings. In the first year of the center’s experience, the Melody prosthesis was reserved as a rescue procedure for failed conventional strategies. However, from the second year onward, it became the standard intervention for all children under 1.5–2 years of age. 

A total of 25 patients underwent Melody prosthesis implantation, with a median age of 6.3 months. Congenital mitral valve disease was the primary indication for surgery in 60% of cases. The majority of patients (84%) had a history of prior valve surgery, either repair or replacement. Mortality at 6 months, 1 year, and 5 years was 8.3%, 12.5%, and 17.6%, respectively. Two patients required early replacement of the Melody prosthesis without subsequent morbidity or mortality. Fifty percent of patients underwent mechanical valve replacement 3.5 years after Melody implantation. 

The authors concluded that Melody prosthesis implantation offers reasonable short-, medium-, and long-term survival with minimal complications, achieving a high success rate in delaying eventual mechanical valve replacement. 

COMMENTARY: 

Mitral valve disease in young children presents a unique challenge, particularly when valve repair fails, making replacement the only solution. This necessitates inevitable reoperations as the child grows, with significant associated morbidity and mortality. These challenges have driven the evolution of surgical strategies, including the use of the Melody prosthesis. This approach allows serial balloon dilations as the child grows, enabling the annulus to accommodate a sufficiently sized mechanical prosthesis in the future. Today, it appears to be the preferred option for patients with annular diameters less than 12 mm and those younger than 1–2 years. 

Another major advantage is the ability to delay anticoagulation, thus avoiding related complications. This cohort demonstrated that no patients experienced thrombotic or bleeding episodes after hospital discharge. In comparison, up to 25% of patients undergoing mechanical valve replacement encounter such complications. Moreover, maintaining therapeutic INR levels in infants is exceedingly difficult. In this study’s cohort, enoxaparin was sufficient during the first 3 months, followed by acetylsalicylic acid until prosthesis explantation. 

Studies described in the literature, both single- and multicenter, report promising survival outcomes. This cohort represents one of the largest single-center experiences with the best-reported survival results to date. It is noteworthy that during the first year, Melody prosthesis implantation was reserved as a rescue procedure for failed conventional treatments in critically ill patients, initially yielding unfavorable results—two patients died early. This prompted a reevaluation of therapeutic strategies, including surgical techniques and decision-making. Subsequently, as indications shifted to exclude decompensated patients and surgical experience improved, the survival curve steadily increased. 

How does this mortality compare? Several studies report high mortality rates (20–25%) in patients under 2 years of age undergoing mechanical mitral valve replacement, primarily due to early and late mortality. This study highlights the survival benefit of Melody prosthesis implantation, achieving a 5-year survival rate of approximately 83%, the best result reported so far. 

In terms of durability, the Melody prosthesis does not offer significant advantages. This study demonstrated rapid valve deterioration in most cases, necessitating early replacement within 2–3 years. This aligns with findings from other studies showing long-term freedom from reoperation in only 30% of cases. Thus, this valve replacement strategy primarily serves to delay anticoagulation initiation and facilitate implantation of a larger, definitive prosthesis. 

In summary, the Melody prosthesis serves as a bridge to accommodate growth, enabling subsequent mechanical valve replacement and reducing associated complications. While it does not eliminate the need for reoperation, it mitigates complications linked to mechanical prostheses in neonates. Despite encouraging results, this study’s limitations include a small sample size and its retrospective, single-center nature. Therefore, caution is warranted, and further randomized studies with larger cohorts and longer follow-ups are needed. 

REFERENCE:

Honjo O, Chetan D, Fan CS, Kadowaki S, Marshall AC, Chaturvedi RR, et al. Surgical Melody Mitral Valve: A Paradigm Shift for Infants With Unrepairable Mitral Valve Disease. Ann Thorac Surg. 2024 Sep;118(3):623-632. doi: 10.1016/j.athoracsur.2024.04.037. Epub 2024 May 27. PMID: 38810907.