Circulation. 1999;100:II-103-II-106
(Circulation. 1999;100:II-103.)
© 1999 American Heart Association, Inc.
Surgery for Valvular Heart Disease |
Pulmonary Autograft Versus Aortic Homograft for Rereplacement of the Aortic Valve
Results From a Subset of a Prospective Randomized Trial
Gerald S. Carr-White, MRCP;
Sally Glennan, REN;
Sue Edwards, BSc;
Francis D. Ferdinand, MD;
Anthony C. Desouza, FRCS;
John R. Pepper, FRCS;
Magdi H. Yacoub, FRS
From the Department of Academic Surgery, National Heart and Lung
Institute, Royal Brompton Hospital, Sydney Street, London, UK.
Correspondence to Prof Sir Magdi Yacoub, Department of Cardiothoracic Surgery, National Heart and Lung Institute, Royal Brompton Hospital, Sydney Street, London SW3 6NP, UK. E-mail g.carr-white{at}rbh.nthames.nhs.uk
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Abstract
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BackgroundThe use of a
pulmonary autograft for rereplacement
of the aortic valve has
both potential advantages and disadvantages.
This study details the
early results of a subset of patients
enrolled in a prospective
randomized trial comparing pulmonary
autografts and aortic
homografts who have had previous aortic
valve replacements.
Methods and ResultsA total of 47 patients who had undergone
1
previous aortic valve replacement were randomized to receive either a
pulmonary autograft (24 patients aged 40±11 years) or an
aortic homograft (23 patients aged 37±11 years) for rereplacement of
the aortic valve. One early death occurred in the homograft group, and
1 late (7 months) death occurred in the autograft group. One patient
who received a pulmonary autograft was reoperated on for
inflammatory pulmonary stenosis. One patient in each
group was reopened for bleeding (both within 24 hours). Two patients in
the autograft group had postoperative neurological weakness; they fully
recovered over 2 months. Hospital stay, blood loss, incidence of
perioperative arrhythmia, and markers of
coronary ischemia were similar between the 2 groups. At
6-month follow-up (range, 1 to 12 months), left ventricular
end-diastolic diameter was similar in both groups
(homografts, 5.0±0.9 cm; autografts, 5.2±0.6 cm;
P=NS), and no patient in either group had significant
aortic valve dysfunction.
ConclusionsRereplacement of the aortic valve with a
pulmonary autograft is feasible and safe in patients aged 14 to
60, regardless of their preoperative diagnosis or clinical
condition.
Key Words: aorta valves autograft surgery
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Introduction
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The mortality and morbidity associated with rereplacement
of
the aortic valve is declining as both surgical technique and
myocardial
protection improve.
1 2 3 4 It is also becoming
increasingly
clear that early reintervention to prevent associated
ventricular
damage produces more favorable
results.
5 6 The ideal valve
substitute, however, remains
unclear. The use of biological
valves offers several theoretical
advantages, including preservation
of the normal aortic valve mechanism
and increased adaptability
in aortic root destruction or distortion.
Although free-standing
homograft root replacements for rereplacement of
the aortic
valve are safe and effective in the short and long
term,
7 concerns
still remain regarding late degeneration
and calcification.
The use of a pulmonary autograft has several
additional theoretical
advantages over homografts,
8 9 10 11 in
particular, the ability
to grow and improved
hemodynamics and durability. However, potential
disadvantages
also exist, particularly in patients who have undergone
previous
aortic valve replacement. These disadvantages include the
increased
complexity and longer duration of the operation. As yet, no
series
has examined the feasibility of using a pulmonary
autograft
for rereplacement of the aortic valve. The objective of this
study
was, therefore, to prospectively compare the effect of
rereplacement
of the aortic valve with an aortic homograft or
pulmonary autograft
on perioperative
variables and short- and medium-term clinical
performance.
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Methods
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Patient Selection
From May 1994 to July 1998, 47 patients were prospectively
randomized
to undergo aortic valve replacement with an aortic homograft
or
a pulmonary autograft as part of a larger ongoing randomized
trial.
12 Local ethical committee approval was obtained
before starting
the study, and full informed consent was obtained from
each
patient. The study included all grades of ventricular
function,
bacterial endocarditis, and emergency operations. Exclusion
criteria
included the need for double-valve replacement or
coronary artery
bypass grafting, connective tissue disorders,
and autoimmune
diseases known to affect the aortic valve and root.
Fourteen
of the 47 patients had previously undergone >1 aortic valve
replacement,
8 had undergone 2 previous replacements, 6 had 3 previous
replacements,
and 1 patient had 6 previous replacements. The patient
demographics,
reasons for reoperation, duration of previous valve
substitutes,
and preoperative ventricular function were
similar between the
2 groups and are illustrated in Table 1

. None of the patients
with
endocarditis had
Staphylococcus aureus as the infecting
organism.
The majority of the patients had failure of previous
homografts,
reflecting the patient population seen in our center.
Operative Technique
All operations were performed by the same surgeon (M.Y.).
Cardiopulmonary bypass with moderate hypothermia (30°C) was
used. In both groups, myocardial protection was achieved by either
antegrade crystalloid or cold blood cardioplegia. Patients were cooled
to 28°C under total cardiopulmonary bypass. Myocardial
preservation was achieved using crystalloid cardioplegia at 4°C (St.
Thomas hospital No. 1) infused through the aortic root or directly
into the coronary ostia. The myocardial temperature (measured
by a myocardial temperature probe placed in the ventricular
septum) was reduced to <10°C. Cardioplegia infusions were repeated
every 20 minutes. The left ventricle was vented through the apex in all
cases.
The aortic valve was exposed through a curved aortotomy, commencing
anteriorly and extending into the middle of the noncoronary
cusp. This allowed excellent exposure of the valve. All patients
underwent aortic root replacement with coronary reimplantation.
The left ventricular outflow tract was reconstructed with
either a homovital or antibiotic sterilized aortic homograft or the
pulmonary autograft. In all cases, an interrupted 4-0 proximal
suture line was used. For coronary reimplantation, continuous
4-0 sutures were used for the distal aortic suture line. In the
autograft group, the right ventricular outflow tract was
reconstructed with a large homovital or antibiotic sterilized
pulmonary homograft (mean size, 25 mm; range, 23 to
28 mm) conduit inserted by continuous 4-0 sutures, without the
inclusion of strips of prosthetic or autologous tissue for
support. These suture lines were placed before release of the aortic
clamp.
In the presence of endocarditis, aggressive and complete debridement of
the infected and necrotic tissue was performed, and no foreign material
was used for reconstruction. This subgroup of patients received
intravenous antibiotics for 6 weeks after the operation.
Even in those patients with endocarditis in whom extensive debridement
of the aortic root was necessary, no additional problems with filling
tissue defects were encountered with root replacements. In all
patients, additional care was necessary in enucleating the
pulmonary autograft due to the frequent dense adhesions to the
scarred aortic root. When necessary, parts of the adherent aortic root
were taken out with the autograft. In all patients, the facing sinus of
the autograft (which is thin and not supported by pericardium) was
placed in the left coronary sinus position of the new aortic
root.
Intraoperative transesophageal
echocardiography was used to monitor valve and
ventricular function before and after insertion of the
graft. Valve function was judged to be good
echocardiographically in all patients immediately after
release of the aortic clamp. X-clamp and bypass times were
significantly longer in the autograft group (132±15 and 194±34
minutes) than the homograft group (98±16 and 136±25 minutes;
P<0.001). Trasylol was used routinely in all patients.
Follow-Up
Early mortality was defined as any death within 30 days or
during initial hospitalization. Postoperative valve-related morbidity
and mortality were evaluated and reported according to standard
definitions.13 All patients had a clinical examination,
chest x-ray, ECG, and color flow Doppler echocardiogram before
discharge, at 6 months, and at yearly intervals after that. Doppler
velocities were calculated at the level of the right and left
ventricular outflow tracts and at the level of the aortic
valve orifice, and mean and peak gradients were derived by the modified
Bernoulli equation. Aortic valve insufficiency was graded according to
the method described by Perry et al.14
Regurgitation not severe enough to be measured by these
criteria was considered trivial. Fractional shortening (FS) was
calculated as FS=[(EDD-ESD)/EDD]x100, where EDD is the
end-diastolic dimension and ESD is the end-systolic
dimension.
Statistical Analysis
Statistical analysis was performed with a commercially
available software package (SPSS Inc). Comparison of demographic and
preoperative data between groups was performed with the use of an
unpaired t test. Comparison of data over time was done with
the use of a 1-way ANOVA. P<0.05 was significant.
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Results
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Mortality
One early death occurred in the homograft group. A 44-year-old
man
with 2 previous Starr-Edwards valve replacements, the last
one in 1987,
developed acute
Streptococcus bovis endocarditis
with
resistant severe heart failure. Twenty minutes after coming
off
bypass, rapidly progressive deterioration in biventricular
function
occurred due to widespread intravascular coagulation with
associated
aortic and intracoronary clot. The cause of the
intravascular
coagulation was not apparent, although Trasylol and
active infection
were assumed to have played a part. One late death
occurred
in the autograft group. A 38-year-old man died suddenly 7
months
after the operation, while participating in a martial arts
class,
due to a cardiac arrhythmia presumed to be
ventricular fibrillation
or tachycardia. At
post mortem examination, both the aortic
and pulmonary valves
were functioning normally.
Reoperation
One patient in the autograft group needed reoperation 18
months postoperatively for pulmonary stenosis. During
the operation, the pulmonary homograft was compressed by
granulation tissue, and subsequent histological and
microbiological examination showed only an inflammatory response, with
no evidence of endocarditis or an underlying cause.
Morbidity
Postoperative complications included re-exploration for
bleeding in 2 patients (1 in each group) and hemiparesis, which
completely resolved over 2 to 3 months, in 2 patients in the autograft
group. No statistically significant differences were identified between
the 2 groups with regard to total blood loss or hospital stay. No
patient in either group had electrocardiographic or biochemical
(creatinine kinase MB) evidence of significant
postoperative myocardial ischemia or infarction. Transient
atrial arrhythmia, which had resolved by discharge, was
present in 5 patients in each group. One patient in each group
developed complete heart block, necessitating implantation of a
permanent pacemaker. Postoperatively, all patients were either in New
York Heart Association class I or II, with no significant difference
between the 2 valve groups (P=0.63, unpaired t
test). No evidence of postoperative endocarditis was seen in either
group.
Hemodynamic Follow-Up
Postoperative echocardiographic evaluation of left
ventricular diameters and aortic and pulmonary
valve function were carried out at regular intervals (Table 2
). Left ventricular
diastolic diameter was reduced in both groups over the
first postoperative year when compared with the preoperative value
(homografts by 22%, autografts by 11%; P=NS by 1-way
ANOVA).
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Discussion
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Previous studies have demonstrated that reoperative aortic valve
replacement
with a homograft root can be performed, with acceptable
early
and late risks.
15 In certain groups of patients,
using a pulmonary
autograft may offer further theoretical
advantages. This study
describes the early results of rereplacement of
the aortic valve
with a pulmonary autograft; this can be
accomplished with acceptable
early- to medium-term mortality and
morbidity. We used biological
valves for second or subsequent aortic
valve replacements in
this study, rather than mechanical valves,
because of the excellent
long-term survival reported in patients with a
similar age distribution
who underwent reoperative aortic homograft
implantation, with
no evidence of accelerated degeneration after the
second operation.
7 16 In addition, we hoped
that using a pulmonary autograft would
improve the acknowledged
life span of aortic homografts. A direct
comparison of biological and
mechanical valves in a prospective,
randomized trial has not, as yet,
been performed. Such a trial
would provide the definitive answer to the
clinical question
of which type of valve substitute is optimal.
Our study population was a subset of an ongoing randomized, controlled
trial, and it was not part of a separate randomization process;
however, we think that the patient groups are similar enough to allow
simple comparisons regarding the short-term safety of using a
pulmonary autograft. Two potential early disadvantages of using
a pulmonary autograft, particularly in patients who have
undergone previous cardiac surgery, are the increased complexity of the
surgery and the increased risk of coronary artery injury. It
is, therefore, reassuring to note that in our group of patients, no
differences existed between the groups with regard to blood loss,
hospital stay, inotrope use, or postoperative myocardial
ischemia. Given the patient numbers involved and the diversity
of ventricular function in patients who have undergone
previous aortic valve replacement, precise comparisons of
ventricular function are impossible. However, in both
groups, left ventricular function seems to be preserved,
with improvement in end-diastolic diameters over the first
postoperative year. In addition, all patients postoperatively are
either in New York Heart Association class I or II.
One patient developed inflammatory pulmonary stenosis,
but the cause of this was unclear. The lack of cusp involvement
or valve destruction suggests that an immunologically mediated
mechanism or occult infection was not the cause; the histologic
examination demonstrated an extrinsic perivalvular inflammatory
infiltrate and suggests a chronic perivalvular inflammatory
process, the cause of which is not known.
This study shows that although pulmonary autograft implantation
is a technically more complex operation in patients having a second or
subsequent aortic valve replacement, it carries a low risk of death and
complications. The mortality and complication rates were comparable to
those for the implantation of either homografts or other substitutes,
both in this study and others.7 15 17 18 Further follow-up
is needed to determine if the potential long-term advantages of
pulmonary autografts are realized. Long-term monitoring of
pulmonary valve and right ventricular function and
neurological events will continue to be important in those who have
undergone pulmonary autograft operations.
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Acknowledgments
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G.S. Carr-White is a British Heart Foundation Junior Research
Fellow,
and M.H. Yacoub is a British Heart Foundation Professor of
Cardiac
Surgery.
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