AT THE 2017 MITRAL VALVE CONCLAVE
NEW YORK (FRONTLINE MEDICAL NEWS) – Repairing mitral valves in pediatric patients must overcome two issues: the wide variability in their anatomy and their growth. Using strategies and techniques common in adult mitral surgery can accomplish good mitral valve function in children, but some techniques in children differ, like using combined resorbable material with autologous tissue or transferring native chords instead of placing artificial chords to a malfunctioning leaflet.
Pedro del Nido, MD, of Boston Children’s Hospital, said the spectrum of mitral valve pathology in children goes from congenital mitral stenosis with a thick annulus with leaflet immobility to leaflet hypermobility that involves anterior leaflet prolapse and can involve a cleft that causes regurgitation. Dr. del Nido explained his surgical approaches for mitral valve disease in children at the 2017 Mitral Conclave, sponsored by the American Association of Thoracic Surgery.
“You have to consider mitral valve disease in kids from the top to the bottom,” Dr. del Nido said. “So think about it from the annulus where there’s a supra-annular ring of tissue that’s restricting the mobility of the leaflets, as well as clefts and holes. The more common pathology that we see with stenosis is subvalvar pathology – fusion of the leaflets, fusion of the leaflet tips of the papillaries to absence of chords.”
Accessing the mitral valve in children requires a different approach than in adults, Dr. del Nido said. “Going through the left atrium is generally difficult, so we often enter through a trans-septal incision,” he said. “The main reason for that is because the tricuspid valve is often associated with the mitral valve problem and this gives us the most direct exposure.”
Once the surgeon gains exposure, the surgical analysis for a diseased adult or child valve is almost identical, with the exception that adult disease is acquired whereas childhood disease tends to be congenital, Dr. del Nido said. “In the congenital patient, we often find fibroelastic tissue that the child is born with,” he said. “We see this in neonates and young infants. It thickens over time; it doesn’t often calcify, but it does often restrict the leaflets and it tends to fuse the chords, so in essence you have direct attachments of the leaflets to the papillaries.”
He explained that this pathology requires an approach similar to that for rheumatic mitral disease in adults. “Start splitting the commissures and start resecting the tissue off the chords creating fenestrations in order to improve the inflow.” Dr. del Nido added, “If you don’t do this, the child will always have a gradient, and if you think about an adult having problems and symptoms with a gradient, think about a 10-year-old running around trying to do athletics; it’s impossible.”
Dysfunctional chords also require a somewhat different approach in children than they require in adults. “We find elongation of the chords and the anterior support structure is abnormal; the secondary chords are totally intact,” Dr. del Nido said. When confronting a torn-edge chord, resection is often an option in adults, but is uncommon in children. “We don’t usually have very much leaflet tissue,” he said. Artificial chords do not accommodate growth.
“We tend to use native tissue,” said Dr. del Nido. “You can transfer the strut chord; you can transfer the secondary chord in order to achieve support for the edge of that prolapsed leaflet.”
Leaflet problems are probably the biggest single source of recurrence in children, Dr. del Nido said. A cleft on the anterior leaflet can be particularly vexing. For example, cleft edges attached to the septum can prevent the valve leaflet from coaptation with the posterior leaflet. “If you don’t recognize that on 3-D echocardiography, you’re going to have a problem; that leaflet will never create the coaptation surface that you want,” he said.
The solution may lie underneath the leaflet. Said Dr. del Nido, “We tend to want to close a cleft, and, yes, that will get you relief of regurgitation in the central portion, but if you end up with immobility of that leaflet, then look underneath. Most often there are very abnormal attachments to the edges of that cleft to the septum. You have to get rid of that; if you don’t resect all that, you’ll never have a leaflet that truly floats up to coapt against the posterior leaflet.”
Annular dilation in children can also challenge a cardiothoracic surgeon’s skill.
In rare cases, a suture commissuroplasty may correct the problem. Sometimes Dr. del Nido will use the DeVega suture annuloplasty – “even though it is very much user dependent; it’s very easy in pediatrics to create stenosis with the DeVega.” As an alternative, synthetic ring annuloplasties can confine valve growth and are rarely used.
Dr. del Nido’s preference is to use a hybrid approach of tissue and resorbable material. “The advantage of the resorbable material is that it will go away, but that’s also the problem with the resorbable material,” he said. “Once it does go away, there’s nothing there to support the annulus, so a combination of tissue and resorbable suture is probably the best answer.”
In posterior leaflet deficiency, a patch of pericardium posteriorly can augment the dysfunctional leaflet. You can also use pericardium as an annuloplasty ring. “You can use it circumferentially,” Dr. del Nido said. “It’s a soft ring; you can certainly use this material which is autologous; it does provide strength to the fibrous annulus; it does support that valve; and you do see growth.” He added that bovine pericardium is not ideal for this use.
Dr. del Nido reported no relevant financial relationships.
