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The history of aortic valve repair with pericardium starts with Yacoub
and Batista who used a single patch of bovine pericardium to construct
an entire tri-leaflet aortic valve in patients with both aortic stenosis
as well as regurgitation (1,2). As little as possible of the free edge
of the leaflet was resected and a large strip of glutaraldehyde-fixed
bovine pericardium was sutured to the cut free edge of the leaflets.
This created very tall leaflets and very high commissures in order to
increase the coaptation of the valve leaflets. However, the excessive
leaflets had a tendency to bend towards the sinuses of Valsalva,
occasionally causing serious coronary ischemia by obstructing coronary
ostia (3).
To keep the leaflets away from the sinuses and avoid the coronary
ischemia, Duran used a plastic container with three consecutive bulges
to mold the shape of the leaflets during fixation (3). Pericardium was
draped over these bulges during glutaraldehyde fixation to give the
neo-leaflets a curved shape facing away from the sinuses. Using this
technique, the group reported a survival of 85% with a mean follow up
of 10.5 years, in a population of patients with a mean age of 31 years.
Freedom from structural valve degeneration was 78% and 55% at 10 and
16 years respectively (4). Interestingly, while initially reported as
aortic valve replacement , it was later labelled as aortic valvereconstruction by the group. Bicuspid aortic valve was a
contraindication.
Dr Ozaki’s technique of “aortic valve reconstruction” (5) is based on
recreating the three leaflets and commissures, rather than extending the
leaflet and commissural heights to increase coaptation. The leaflets are
completely excised and replaced with three separate pieces of autologous
glutaraldehyde-fixed pericardium. New leaflets are sutured directly to
the annulus. Even bicuspid valves are repaired in a tri-leaflet fashion
by creating a new commissure. While he has demonstrated excellent
midterm results, the mean age of the patients was 71 years. Even though
this procedure can be done minimally invasively (6), this is the age
group in which transcatheter aortic valve implantation has become the
procedure of choice in the western world. Ozaki procedure is therefore
unlikely to see widespread use in this older patient population.
However, in the developing world, where millions of patients still
suffer from rheumatic valvular disease and up to 12-13 million patients
suffer from rheumatic aortic valve disease (7), this procedure has
tremendous potential. There have been reports of its successful use in
Brazil, Russia and Vietnam (6-9) for instance, where the population has
been relatively younger. In this issue of Journal of Cardiac
Surgery, Ngo et al (10) from Vietnam, presents their experience with
Ozaki procedure in 72 patients with a mean age of 53 years and mean
follow-up of 26 months. Two patients required conversion to prosthetic
valve replacement due to coronary obstruction with reconstructed
leaflets. There was one 30-day mortality due to cardiac tamponade from
bleeding and another two died due to pseudoaneurysm rupture resulting
from mediastinitis. In the follow-up period, two patients required
reoperation for infected endocarditis. Only one patient had moderate
regurgitation immediately following surgery and should be considered a
failure of the operation. None of the other complications can be
attributed to the procedure itself. These results are comparable to
those of others (6-9).
When Dr Ozaki presented his initial series of patients, the concern was
reproducibility. However, with the creation of “AVNeo” system, which
uses standardized sizing templates for the autologous pericardium based
on inter-commissural distance and coaptation heights, this procedure has
become quite reproducible. This work by Nguyen et al, is a testament to
the reliability and reproducibility of the Ozaki procedure or
Neo-cuspidization as it is also called.
Another potential use of this procedure is in the pediatric population.
Since its approval by Food and Drug Administration approval in 2014, it
has also been used in pediatric patients (11). By not restricting the
aortic root, this procedure allows the aortic root to grow with age.
Since 2015, pediatric sizers 13 mm and 15 mm have also been available in
addition to the adult sizes 17 to 31 mm.
One issue that still remains unresolved is the fate of the autologous
pericardial leaflets over long term. Dr Duran’s report of 92 patients
(5) remains the most pertinent report on the use of autologous
pericardium in a young population. The mean age of patients in that
series was 30 years and it had a mean follow up of 10 years. The group
had a survival of a 85% over a 10 year follow-up. Ozaki procedure has
not been tested in such a young population yet.
One final consideration is the choice of material for leaflet
reconstruction. Much research is being conducted on the use of synthetic
materials such as polyurethanes and nanocomposite polymers, as well as
carbon fibers for use in prosthetic valves. These materials have shown
promising results (12-14) in vitro in terms of their durability,
resistance to thrombosis and ability to encourage endothelialization. It
would be logical to use some of these materials in making individual
leaflets that can be kept on the shelves and used when needed, instead
of autologous pericardium. It would save time as well as be amenable to
minimally invasive approaches. I hope someone picks up on this line of
research, with the hope of having artificial leaflets of all different
sizes on the shelf for use in the young adult population.
In conclusion, this procedure is a useful tool in the surgeon’s
armamentarium, but its most beneficial use will be in a younger
population under the age of 50 years, where it still has to demonstrate
long-term freedom from structural valve degeneration. More centers need
to report even longer-term outcomes in a young adult and pediatric
population to clearly define its role in the treatment of aortic valve
disease. Use of synthetic leaflets as an alternative to autologous
pericardium would be a reasonable line of future investigation but does
not seem to be the focus of any published literature yet. At present
this procedure can be best described as what my friend and mentor, Dr
John Charles Alexander loves to quote, “Close, but no cigar.”
REFERENCES:
- Yacoub M, Khaghani A, Dhalla N, et al. Aortic valve replacement using
unstented dura or calf pericardium: early and medium term results. In:
Bodnar E, Yacoub M, Eds. Biological and bioprosthetic valves.New York: Yorke Medical Books, 1986:684-90
- Batista RJV, Dobrianskij A, Comazi M, et al. Clinical experience with
stentless pericardial aortic monopathy for aortic valve replacement.J Thorac Cardiovasc Surg 1987;99:113-8
- Duran CMG, Gometza B, Kumar N, Gallo R and Martin-Duran R. Aortic
valve replacement with freehand autologous pericardium. J Thorac
Cardiovasc Surg 1995;110:511-6
- Halees Z, Shahid MA, Sanei AA, Sallehuddin A and Duran C. Up to 16
years follow-up of aortic valve reconstruction with pericardium: a
stentless readily available cheap valve? Eur J Cardiothorac
Surg 2005;28(2):200-5
- Ozaki S, Kawase I, Yamashita H, Uchida S, et al. Aortic valve
reconstruction using self-developed aortic valve plasty system in
aortic valve disease. Interact CardioVasc Thorac Surg2011;12:550-3
- Nguyen DH, Vo AT, Le KM, et al. Minimally invasive Ozaki procedure in
aortic valve disease: Preliminary results. Innovations (Phila)2018;13(5):332-7
- Coffey S, Robert-Thomson R, Brown A, et al. Global epidemiology of
valvular heart disease. Nature Rev Cardiol 2021;18:853-64
- Ozaki S, Kawase I, Yamashita H, et al. Midterm outcomes after aortic
valve neocuspidization with glutaraldehyde-treated autologous
pericardium. J Thorac Cardiovasc Surg 2018;15(6):2379-87
- Krane M, Boehm J, Prinzing A, et al. Excellent hemodynamic performance
after aortic valve neocuspidization using autologous pericardium.Ann Thorac Surg 2021;111:126-33
- Ngo TH, Nguyen CHG, Do DT et al. Aortic valve reconstruction surgry
using autologous pericardium: The experience in Vietnam. J
Cardiac Surg ………….
- Baird CS, Marathe SP and del Nido PJ. Aortic valve neo-cuspidation
using the Ozaki technique for acquired and congenital disease: where
does this procedure currently stand? Ind J Thorac Cardiovasc
Surg 2020;36(1):S113-22
- Ovcharenko EA, Seifalian A, Rezvova MA, et al. A new nanocomposite
copolymer based on functionalised graphene oxide for development of
heart valves.
www.nature.com/scientificreports/
2020;10:5271, https://doi.org/10.1038/s41598-020-62122-8 ,
Accessed January 16, 2022
- Alves P, ardoso R, Correia TR, et al. Surface modification of
polyurethane films by plasma and ultraviolet light to improve
haemocompatibility for artificial heart valves. Colloids and
Surfaces B: Biointerfaces 2014;113:25-32
- Tseng Y-T, Grace NF, Aguib H, et al. Biocompatibility and application
of carbon fibers in heart valve tissue engineering. Front
Cardiovasc Med 8:793898
doi: 10.3389/fcvm.2021.793898. Accessed January 14, 2022.