Argano, Vincenzo

Totaro, Pasquale

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size 31-mm stented control valve. We ac-
tually tested 10 valves in each category of
small (19 mm), medium (25 mm) and large
(29 mm) sizes for a total of 30 wear tests.
Furthermore, to provide a more rigorous
trial for the valve, we tested it against the
SJM Toronto SPV (St Jude Medical, Inc, St
Paul, Minn), a stentless valve approved by
the FDA for commercial distribution in the
United States. We note that Mr Biancucci
did not challenge the accuracy of the data
that we reported for accelerated wear test-
ing in the article.
We agree with Mr Biancucci that the
paragraph titled “Visualization of Flow
Across the 3F Aortic Bioprosthesis” that
appears in the Results section of the paper
is technically incorrect in that it states that
we performed flow visualization studies in
valves other than the 19-mm valve size.
However, the unintentional and harmless
nature of this error is verified by the fact
that in that same paragraph we stated that
we used the smallest size valve (19 mm) in
the stiffest aortic testing chamber (4%
compliance) to illustrate the lack of turbu-
lence shown in Figures 4 and 5. In fact, the
FDA-sanctioned protocol, to which we
were meticulously adhering, called for the
testing of 19-mm valves only, because of
their predictably higher Reynolds numbers
and the scientifically acceptable practice of
extrapolating the lack of turbulence ob-
served in our small 19-mm valve to its
larger sizes without having to test the larger
sizes individually. Thus, the information
reported in the article relating to the lack of
turbulence associated with the 3F Aortic
Bioprosthesis is scientifically accurate and
conforms precisely to the FDA testing
protocol.
Again, rather than challenging the fun-
damental truth, accuracy, and/or interpreta-
tions of the finite element analysis studies,
Mr Biancucci chose to attack the technical
aspects of the manuscript. The original
studies were performed in 1991 to validate
or refute the concept of the tubular pros-
thesis and, as clearly shown in Figure 10,
confirmed that the greatest degree of stress
on a simple tube, subjected to the same
anatomic constraints as the native aortic
valve, occurs in the belly of the resultant
tubular “valve” and the least degree of
stress occurs where the commissural posts
of that tubular “valve” would be. The ab-
solute levels of stress on that hypothetical
tubular valve were far greater than the ab-
solute levels of stress that occur with the
actual 3F Aortic Bioprosthesis in its final
tubular design (Figure 6).
The relative stress scale shown beside
the valve leaflet in Figure 6 clearly shows
at the right side of the figure that the com-
missural region from the bottom to the top
is virtually stress free with only minor
stress along the leading edge of the leaflet
that disappears as it nears the region of the
commissural tab. It is possible that Mr Bi-
ancucci is referring to the minor stress on
the left side of the figure that appears to be
in the commissural attachment area but is
only so due to the orientation of the view.
Perhaps a quick review of the magnitude
and distribution of stress on currently avail-
able artificial tissue valves would enlighten
Mr Biancucci to the potential of the 3F
Aortic Bioprosthesis to extend the life of
artificial tissue valves.
Finally, in none of his comments, with
the possible exception of those directed at
the finite element studies, did Mr Biancucci
challenge the accuracy of the reported data
or of our interpretations of the data. Mr
Biancucci states in his closing paragraph
that his criticisms “are not intended to be
petty or esoteric.” There is little wonder
that he felt it necessary to add that dis-
claimer. Mr Biancucci may not be enam-
ored with the concept that underlies this
valve or with its tubular geometry, but the
objective observations described in our ar-
ticle would seem to trump his subjective
opinion. Furthermore, we question his
qualifications to lecture us, and by impli-
cation the editors and reviewers of the
Journal of Thoracic and Cardiovascular
Surgery, on the importance of producing
“intellectually and scientifically rigorous”
papers. One of the criteria of intellectual
honesty is to reserve authorship on scien-
tific papers to those contributors who have
earned it, a criterion that we are confident
was satisfied with the publication of this
article.
James L. Cox, MDa
R. C. Quijano, MD, PhDb
Division of Cardiothoracic Surgerya
Washington University School of Medicine
St Louis, Mo
3F Therapeutics, Incb
Lake Forest, Calif
References
1. Biancucci B. Tubular heart valves. J Thorac
Cardiovasc Surg. 2006;131:1419.
2. Cox JL, Ad N, Myers K, Gharib M, Quijano
RC. Tubular heart valves: a new tissue pros-
thesis design—preclinical evaluation of the
3F aortic bioprosthesis. J Thorac Cardiovasc
Surg. 2005;130;520-7.
doi:10.1016/j.jtcvs.2006.08.103
Improved prosthesis–annulus
interaction and postoperative
hemodynamic performance of
new-generation aortic bioprosthesis
To the Editor:
We read with extreme interest the arti-
cle, “Small Aortic Annulus: The Hydro-
dynamic Performances of 5 Commercially
Available Tissue Valves,” published in the
May 2006 issue of the Journal.1 We would
like to congratulate Gerosa and coauthors
for the well-designed study, but we would
also add some brief comments. The authors
evaluated in vitro performances of 5 bio-
prosthesis designed for supra-annular im-
plantation and showed improved perfor-
mances of the Mitroflow valve compared
with the CE Perimount Magna (for cardiac
output  5 L/min). Inasmuch as the nom-
inal size is not uniform for different pros-
thesis, they compared the size of each type
fitting a 21-mm mounting ring (mimick-
ing a 21-mm aortic annulus). The concept
of supra-annular design is, however, dif-
ferent for the different prosthesis used in
the study. As we2 recently showed, the CE
Perimount Magna, the new generation of
CE Perimount characterized by a new sew-
ing cuff, allows the implantation of a big-
ger size prosthesis than does the standard
CE Perimount valve in almost 50% of pa-
tients. This is due to the improved interac-
tion between the new sewing cuff and the
aortic surgical annulus, which is not a flat
plane. This improved annulus-prosthesis in-
teraction could also explain the improved
in vivo performance of the CE Perimount
Magna when compared with the standard
CE Perimount valve of the same size, even
though the valve itself (housing and leaf-
lets) is not changed.
The supra-annular concept of the Mitro-
flow valve is different inasmuch as the
sewing ring is on a flat plane. The mount-
ing ring used in the study from Gerosa and
coauthors is also on a flat plane, and this
may have influenced the results of the study.
In vitro hemodynamic performances of the
CE Perimount Magna valve reported in this
study, in fact, do not reflect in vivo hemo-
Letters to the Editor
846 The Journal of Thoracic and Cardiovascular Surgery ● March 2007
dynamic performances that we reported in
our study and that were also confirmed by
other authors.3 This is quite unusual be-
cause, as the authors also state in their
article, the in vitro effective orifice areas
usually tend to overestimate the in vivo
effective orifice areas. Furthermore, hemo-
dynamic performances reported by Gerosa
and coauthors do not reflect the in vitro
hemodynamic performances reported for
the CE Perimount standard valve by Mar-
quez, Hon, and Yoganathan,4 even though,
as we already stressed, the valve itself is
not changed.
In conclusion we agree with the authors
that in vivo hemodynamic behavior of a
valve might differ from our idealized as-
sumption. However, we do believe that in
the case of prostheses with a supra-annular
design, such as the CE Perimount Magna,
in vivo performances could be improved
owing to the improved annulus-prosthesis
interaction. In vitro tests, like those re-
ported in this study, are extremely useful in
evaluating opening mechanism as well as
descriptive parameters for each prosthesis.
However, a real comparison of hemody-
namic performances of two valves with
such a different design as the Mitroflow
and CE Perimount Magna can be made
only in a randomized study evaluating cu-
mulative mean postoperative effective ori-
fice areas for two groups.
Pasquale Totaro
Vincenzo Argano
Cardiac Surgery Division
Morriston Hospital
Swansea, United Kingdom
References
1. Gerosa G, Tarzia V, Rizzoli G, Bottio T.
Small aortic annulus: the hemodynamic per-
formances of 5 commercially available tissue
valves. J Thorac Cardiovasc Surg. 2006;131:
1058-64.
2. Totaro P, Degno N, Zaidi A, Youhana A, Ar-
gano V. Edwards Perimount Magna: a stented
valve with stentless performances? J Thorac
Cardiovasc Surg. 2005;130:1668-74.
3. Botznenhardt F, Eichinger WB, Bleiziffer S,
Gunzinger R, Wagner IM, Bauernschmitt R,
et al. Hemodynamic comparison of biopros-
theses for complete supra-annular position in
patient with small aortic annulus. J Am Coll
Cardiol. 2005;45:2054-60.
4. Marquez S, Hon RT, Yoganathan AP. Com-
parative hydrodynamic evaluation of biopros-
thetic heart valves. J Heart Valve Dis. 2001;
10:802-11.
doi:10.1016/j.jtcvs.2006.10.052
Reply to the Editor:
We appreciate the comments of Drs Totaro
and Argano on our recent article reporting
in vitro performances of 5 different aortic
tissue valves designed for supra-annular
implantation.1 To our minds, Drs Totaro
and Argano raised more questions than
comments, and we will discuss them in this
reply.
Supra-annular concept. During aor-
tic valve surgery, one of the main end points
should logically be to relieve as much steno-
sis as possible by ensuring that the indexed
effective orifice area (EOA) after the opera-
tion is above 0.85 to 0.90 cm2/m2.2 Hence, it
seems logical to implant supra-annular valves
that are placed on top of the aortic annulus.3
The Medtronic Mosaic, Carpentier-Edwards
Magna, Sorin Soprano, SJM-Biocor-Epic-
Supra, and Mitroflow valves all belong to
this category of prostheses. The concept of
supra-annular design is exclusively related
to the placement of a specifically designed
prosthesis, whether mechanical or biologi-
cal, on the top of the aortic annulus. The
patient annulus-prosthesis stent interaction
may explain why different valves are more
easily implanted than others, such as the
Sorin Soprano4 and the Mitroflow valves,
which have a flat profile. However, it can-
not explain differential hydraulic perfor-
mances. Unfortunately, at present, the hy-
pothetical differential hydraulic behavior
between different prosthetic heart valves
has not yet been sufficiently and compre-
hensively revealed.
The mounting ring of the pulse
duplicator may have influenced the
results. We tested production quality bio-
prostheses including the sewing ring cuffs
secured in between the 2 O-rings of the
pulse duplicator holder. To allow a mean-
ingful comparison regardless industry-la-
beled valve size, we tested the supra-annu-
lar tissue valves with a tissue annulus
diameter that could be fit in a 21-mm pulse
duplicator ring. Owing to the supra-annular
configuration, the opposite ring to fix the
valve measured a size larger than the first
(23 mm), therefore mimicking patient an-
nulus-prosthesis interaction. The valves
and the holder were sealed before testing.
We agree with Drs Totaro and Argano that
the pulse duplicator holder has a flat pro-
file. Nevertheless, we selected a relatively
homogeneous group of valves by using
those with the largest tissue annulus diam-
eter that could be superimposed in a defi-
nite pulse duplicator ring, without forcing
the insertion, to avoid stent modification.
We are fully aware that the distortion of the
normal planar geometry of the pericardial
prosthesis, induced by fixation with a sec-
ond inadequate ring, may result in failure
of adequate central leaflet coaptation. This
was not the case in our study. Unfortu-
nately, Totaro and Argano failed to con-
structively and fully explain how the
mounting ring of the pulse duplicator may
influence the comparison of different tissue
valves analyzed under identical conditions.
Our in vitro hydrodynamic perfor-
mances do not reflect the in vivo re-
sults reported by Totaro and associ-
ates.5 The EOA, the most commonly used
parameter for prosthetic heart valve com-
parison, is usually calculated by dividing
the flow measured in the left ventricular
outflow tract by transvalvular velocity.
Meanwhile, whereas the EOA was initially
believed to be a flow-independent parame-
ter, Kadem and coauthors6 recently sug-
gested that it is actually a flow-related pa-
rameter. Therefore, the predominance of
unsteady effects at low flow rates may be
further considered in measuring prosthetic
EOA.6 Moreover, as recommended by the
American Society of Echocardiography,7
measurements should be made over 3 cy-
cles in sinus rhythm or over 6 cycles in
atrial fibrillation. It is further suggested that
regurgitant jets also be calculated. These
should be localized and then graded by a
combination of the diameter of the base of
the jet and the density and slope of the
aortic regurgitant signal. Additionally, fo-
cusing on prosthetic heart valve compari-
son, the in vivo values should ideally be
measured 1 year after the operation, be-
cause the latter may change during the first
postoperative year.2 Concerning the pres-
sure recovery phenomenon, it has been
shown that mild stenosis, such as in a pa-
tient with a prosthesis, and a small aortic
root may lead to confounding echocardio-
graphic results.8 Pibarot and Dumesnil2
also observed that the impact of a mis-
match may be overestimated in these pa-
tients; thus, under the same indexed EOA,
patients with a smaller aorta will have less
energy loss and less burden on their left
ventricle than those with a larger aorta.
To summarize, unfortunately, in vivo
studies are not only limited by echocardio-
graphic technical pitfalls, but also different
clinical setting may intervene, leading to
Letters to the Editor
The Journal of Thoracic and Cardiovascular Surgery ● Volume 133, Number 3 847


Improved prosthesis–annulus interaction and postoperative hemodynamic performance of new-generation aortic bioprosthesis 

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Improved prosthesis–annulus interaction and postoperative hemodynamic performance of new-generation aortic bioprosthesis

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