Melody® Valve in the Mitral Position
The Melody® valve was designed to replace failing pulmonary valves. When there was no other option for some infants and toddlers with severe mitral valve disease (a different valve in the heart altogether), doctors at Boston Children’s Hospital placed Melody® valves surgically in these children’s mitral positions in order to give them a chance at life.
The following information about infants and toddlers with severe mitral valve disease, and specifically about the use of the Melody® valve in the mitral position, was provided by cardiologists and surgeons from the Heart Center at Boston Children’s Hospital.
What is mitral valve disease?
Mitral valve disease, both obstruction and leakage, is a rare but often fatal problem in infants and children. If left untreated, mitral valve disease can lead to problems with lung function and severe heart failure.
What are the current options for patients with mitral valve disease besides replacement?
Mitral valve balloon dilation and surgical repair are the preferred methods of treatment for children with mitral valve disease. Because the children keep their own native valves, these options allow for growth of the valve as the child grows. However, in some children, the valve is so distorted that dilation or repair is not possible. If left untreated, these children will develop irreversible problems with lung function and heart function, often leading to heart failure. Surgical valve repair is particularly treacherous in very young children.
Can you replace the valve if it’s not repairable?
Mitral valve replacement is often the only option for children with irreparable valves. In adults, there are many options for mitral valve replacement including mechanical valves and biological valves. However in children, there are very limited options. There are no valves less than 12 mm in size that are commercially available. The smallest valve is a 15 mm mechanical valve. This means essentially no options for children under one year of age, and limited options for most children under five years of age. And, the options currently available can lead to other serious health challenges.
For example, mechanical valves require the blood thinner Coumadin, which is very difficult to administer correctly to children and requires very careful monitoring. If for some reason the blood thinner levels are not accurate, the child can develop clots that lead to stroke. Recent studies from Atlanta and Indianapolis show that complications are common after mitral valve replacement with a mechanical valve in up to half of patients.
There are some options for biological valve replacement, but all of these valves are fixed in size, and therefore require reoperation for replacement as the child grows. The group from Indianapolis also found that mitral valve re-replacement was more common in younger children, since they tend to outgrow their valve much more rapidly. In other words, these children continue to need open-heart surgeries as they outgrow these fixed-sized valves.
Even worse, surgical placement of an artificial rigid valve (which these are) in a child’s heart arrests the growth of that part of the heart, making re-replacement much more difficult and less effective. What this means is that once a fixed-size valve is placed, the child usually cannot get valves big enough in the future to allow them sufficient heart function to grow into adulthood.
How can the Melody® valve fix this problem?
There are several advantages to the Melody® valve in the mitral position. Its size is adjustable, so it can be implanted in very young children—the Melody® has been placed successfully in a child as young as age three weeks—and expanded as the child grows.
The Boston Children’s Hospital group has demonstrated that the Melody® valve in the mitral position functions well at sizes as small as 9 mm (which means even newborns have received them), and can be enlarged non-surgically using dilation techniques over time, thus avoiding multiple re-operations for these fragile children. Unlike mechanical valves, the Melody® does not require blood thinners. Although we don’t have very long-term data yet, the results after the first three years in the first 18 patients are promising.
What are the obstacles to using the Melody® valve for valve replacement in small children?
The valve is designed for use in older children and adults, specifically for replacing the pulmonary valve through a catheter technique, not through open-heart surgery. Surgeons have to modify the valve in order to use it in the mitral position. Making these modifications can be tricky, and potentially places the valves at risk for failure down the road.
The necessary modifications made by surgeons make later dilations more difficult, and potentially more dangerous. Also, the Melody® is not formally FDA approved as a humanitarian device for infants and children with mitral valve disease, so surgeons are unlikely to use it for these patients. A commercially-designed valve would remove variability in design, meaning the modifications will be made before they reach the surgeons, making the valve safer, and making it available for widespread pediatric use.
Finally, we do not know the long-term results of the Melody® or what challenges may arise long-term simply because it is newer. But alternative treatments in many cases are unavailable, ineffective, or associated with substantial risks to patient safety.
To learn more about the valve itself, visit the Medtronic website.
For general information regarding pediatric mitral valve disease, visit this page.
Research relevant to Melody® valve in the mitral position:
1: Beierlein W, Becker V, Yates R, Tsang V, Elliott M, de Leval M, van Doorn C. Long-term follow-up after mitral valve replacement in childhood: poor event-free survival in the young child. Eur J Cardiothorac Surg. 2007 May;31(5):860-5. Epub 2007 Mar 26. PubMed PMID: 17383889.
2: Brown JW, Fiore AC, Ruzmetov M, Eltayeb O, Rodefeld MD, Turrentine MW.Evolution of mitral valve replacement in children: a 40-year experience. Ann Thorac Surg. 2012 Feb;93(2):626-33; discussion 633. doi: 10.1016/j.athoracsur.2011.08.085. Epub 2011 Dec 7. PubMed PMID: 22153051.
3: Quiñonez LG, Breitbart R, Tworetsky W, Lock JE, Marshall AC, Emani SM. Stented bovine jugular vein graft (Melody valve) for surgical mitral valve replacement in infants and children. J Thorac Cardiovasc Surg. 2013 Dec 9. pii: S0022-5223(13)01289-0. doi: 10.1016/j.jtcvs.2013.10.059. [Epub ahead of print] PubMed PMID: 24332108.
4: Kanter KR, Kogon BE, Kirshbom PM. Supra-annular mitral valve replacement in children. Ann Thorac Surg. 2011 Dec;92(6):2221-7; discussion 2227-9. doi: 10.1016/j.athoracsur.2011.06.023. Epub 2011 Oct 1. PubMed PMID: 21962266.