How Our Pediatric Heart Surgeons Decide Between Aortic Valve Repair Techniques in Complex Cases
Learning your child needs aortic valve surgery can fill your mind with “what ifs.” Suddenly, you must absorb gobs of complicated medical information and make crucial decisions about their health and future. The circumstances require a crash course in anatomy and cardiology; you must become an expert in conditions and treatments, read up on state-of-the-art advancements.
The questions never seem to end, and good information is tough to find outside the exam room. Complex malformations of the aortic valve are never exactly the same, and you quickly learn there are various methods to repair them, like synthetic patches, animal-derived patches, cow/pig valves, mechanical valves, tissue-engineered valves.
Each method solves different aortic problems in different ways.
Treatment of complex aortic valve disease involves removal and replacement of the diseased aorta. It’s a complicated surgery that demands highly personalized consideration beforehand. Attention must be paid to growth, anatomy, health, lifestyle, family, and the long future ahead. In children, a valve needs to be able to function for 80 years.
At the crux of consideration is the type of operation itself. For decades, the Ross technique has been the gold standard of aortic valve replacement. And then, about a decade ago, a new method came along: the Ozaki technique. Even among surgeons, the assumption of rivalry was born—one must be better, right?
Well, no, not exactly, says David Kalfa, MD, PhD, pediatric heart surgeon, Director of the Pediatric Heart Valve Center and Director of the Initiative for Pediatric Cardiac Innovation. The Ross and Ozaki techniques are not rivals, but allies.
“It’s about patient selection,” says Dr. Kalfa. “They answer different needs for different populations.” While the Ross technique may be the best method of repair in one child, Ozaki could serve the needs of the next in equal measure.
To understand the selection process, let’s break down the difference between these surgical methods, conceptually—
The Ross procedure uses your child’s own living tissues. Surgeons remove the diseased aortic root and replace it with your child’s healthy pulmonary root, the only method with a living substitute. The pulmonary valve is then replaced with a cadaveric, bovine, or artificial conduit.
Implanting living tissues (called autograft) have inherent anatomical benefits, down to the cellular level, that eliminate the possibility of rejection-like reactions. There is no need for long-term medications afterward. And most importantly, this is a living valve that can grown with the child.
“The valve root is a complex structure in terms of architecture, histology, and how it works,” says Dr. Kalfa. “There is very specific deformation in the root during blood ejection, so you can replicate this type of deformation, hemodynamics and mechanical performance with the Ross procedure because you are using an autologous living valve: the pulmonary autograft.”
Living replication provides complex functionality: excellent hemodynamics, resistance to infection, low thrombogenicity (the tendency to produce a clot when in contact with blood), and laminar flow (the normal condition of smooth and constant blood flow in the aorta).
It all has to do with the living tissue’s complex three-layered architecture. A leaflet is made of three layers, each with different components: collagen in the upper layer, elastin in the lower layer, and specific proteins in the middle for stress absorption.
“Because of this very specific architecture, the valve has optimized mechanical properties to do what it needs to do,” says Dr. Kalfa. “It’s what we call anisotropy, meaning the tissue has different properties depending on which direction you pull it.” No non-living alternative currently available can replicate such complex mechanical properties.
The native aortic valve leaflet—taken from the pulmonary valve—used in a Ross procedure grows with the body and has fantastic outcomes. In fact, the long-term rates of survival in those who received the Ross procedure are equivalent to that of the general population, those without any cardiac intervention whatsoever.
Even the gold standard has its drawbacks. The operation is longer, riskier, and few surgeons can actually do it. Further, future intervention to replace or repair the pulmonary conduit are likely as it can deteriorate or become blocked over time.
On the other hand, the Ozaki technique is a standardized procedure that has other advantages. Instead of using a living structure, new aortic leaflets are constructed using different materials, leaving the healthy pulmonary valve intact.
In the Ozaki approach, the diseased aortic valve is removed and recreated via leaflet templates (standardization) with a tissue substitute taken from the patient’s own pericardium or bovine pericardium.
“The Ozaki is an attractive shorter, less extensive operation that doesn’t preclude us from doing a Ross down the road or using a mechanical valve.” says Damien LaPar, MD, pediatric heart surgeon.
Since the Ozaki does not replace the aorta with living tissue, lifelong daily aspirin is prescribed, but dependence on anticoagulants is not required. “For patients at higher risk, the Ozaki method can be a great option,” says Dr. Lapar. “Our kids spend less time on bypass, and the method preserves the normal contributions of the aortic root, unlike mechanical or synthetic options.”
Outcomes data for the Ozaki procedure is all still very recent. The first Ozaki procedure in a child occurred in 2011, compared with the Ross method, which was first introduced in 1967. “That’s why you can’t really compare the data,” says Dr. Kalfa who trained under Dr. Shigeyuki Ozaki. “We know that the Ross has great survival compared to others, but we just don’t have comparable data for the Ozaki, yet.”
Patient selection depends on a variety of medical factors. When the Ross procedure is not an option for a higher risk child, or won’t bring the best possible outcomes, the Ozaki method becomes a supremely valuable choice.
“For children with aortic stenosis or regurgitation, rheumatoid or connective tissue diseases, we would not recommend a Ross procedure,” says Dr. Kalfa. “That’s the population in which the Ozaki is leading. We’ve seen great outcomes in patients with aortic stenosis or aortic insufficiency.”
“When we discuss these options with parents, we put it all on the table, every pro and con,” says Dr. Kalfa. “Right now, there is no perfect patch. We know that at some point the current patches will fail in one way or another.”
That’s why the Ross procedure, that is based on a living valve and living tissue, remains the gold-standard for aortic valve replacement in growing neonates, infants, children, and adolescents.
The Ozaki is a reproducible and promising option for kids in which the Ross is not feasible—for now.
“In my lab [Pediatric heart valve Research Lab], we are working on creating a new type of patch that would actually mimic the exact architecture and exact mechanical properties of the native valve,” says Dr. Kalfa. “If we can replicate it and make a patch that can last, then maybe the Ozaki could be the perfect option.”
Learn more about the Pediatric Heart Valve Center here or call (212) 305-5975.