Circulation. 1995;91:257-261
(Circulation. 1995;91:257-261.)
© 1995 American Heart Association, Inc.
Importance of Initial Coronary Artery Flow After Heart Procurement to Assess Heart Viability Before Transplantation
René Ferrera, PhD;
Rémi Forrat, MD;
Peter Marcsek, MD;
Michel de Lorgeril, MD;
Georges Dureau, MD
From the Institut National pour la Santé et la Recherche
Médicale, Unit 63 (R.F., M.L.), Centre de Transfusion Sanguine (P.M.),
and Hôpital Cardiologique (G.D.), Lyon, France.
Correspondence to Dr R. Ferrera, INSERM—Unité 63, 22, Ave du
Doyen Lépine—Case 18, 69675 Bron Cedex, France.
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Abstract
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Background The objective of this study was to evaluate
different
tests of heart viability in a pig model of warm ischemia.
Methods and Results Pig hearts (n=30) were submitted to 0
(= group I), 10 (group II), 20 (group III), 30 (group IV), and 60
(group V) minutes of in situ warm ischemia (animal exsanguination).
Hearts were removed, then flushed with cardioplegic solution for 3
minutes at a fixed pressure of 60 cm H2O, and edema
formation, initial coronary flow, and ionic composition
(Na+, K+, and Ca++)
of coronary sinus effluent were evaluated. Hearts were then stored for
2 hours in a cold (4°C) preservation solution. Myocardial biopsies
(and evaluation of energetic index) were performed, then the hearts
were reperfused for 30 minutes with whole blood with an in vitro
functional testing system. No edema occurred during cardioplegic flush
in the hearts in groups I through IV, but a 37±11% weight increase
(P<.001) occurred in hearts in group V. There was a
progressive decrease in initial coronary flow with the increase in the
duration of warm ischemia (70±14 mL/min per 100 g of tissue in group I
and 52±9, 41±16, 25±11, and 23±5 mL/min per 100 g,
respectively, in
groups II through V (P<.01 to P<.001 versus
group I). Initial coronary flow was positively correlated with the
energetic index (r=.84, P<.001), and the left
ventricle developed pressure at reperfusion (r=.90,
P<.001). Finally, there were significant differences
between hearts in the control group and those in group V for calcium
and sodium release (lower in the control group; P<.001 and
P<.01, respectively) and for potassium removal (lower in
group V, P<.05).
Conclusions These data suggest that early measurement of
coronary flow after removal of the heart may help to assess heart
viability before transplantation. This approach may provide a
comprehensive clinical evaluation to increase the number of hearts
available for transplantation among those that are rejected in the
absence of accurate criteria of viability.
Key Words: myocardium • ischemia • reperfusion • edema • transplantation
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Introduction
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Although there is a tragic lack of hearts
available for transplantation,
some hearts are rejected because of the
absence of objective
criteria of viability. There is no simple in vitro
test that
can predict heart function after orthotopic transplantation.
In
fact, the only test available for assessment of myocardial viability
for
transplantation is transplantation itself. Thus, pretransplant
investigation
of graft viability appears to be a major challenge of
transplantation.
1 Proctor et al
2 suggested
that coronary artery resistance during
hypothermic perfusion may be
used to assess heart viability,
and Suros and Woods
3
showed that a 60% increase in coronary
resistance was associated with
irreversible myocardial damage.
Watson et al
4 reported a
relation between coronary artery flow
during hypothermic perfusion and
graft viability after transplantation.
Other studies have suggested
that an increase in coronary artery
resistance is related to platelet
and vascular thromboxane production,
5
adenosine,
6 or free radical formation.
7 The
degree of myocardial
edema was also proposed as a viability test.
Guerraty et al
8 suggested that a 25% gain in heart weight
may be a criterion
of irreversible damage after heart preservation. On
the other
hand, Wicomb et al
9 and Cooper et
al
10 reported that myocardial
edema was not deleterious
for the heart during hypothermic preservation.
Others reported that
ventricular compliance
11 12 13 or
intramyocardial
pressure
14 could be useful for assessment of graft
viability. However,
these conflicting data need to be confirmed before
they are
used in a clinical setting. Any test to assess heart viability
must
be reliable, nontraumatic, and easy and rapid to perform under
clinical
conditions. The main objective of the present
investigation
was to study edema formation, early coronary artery flow,
and
electrolyte exchanges during harvesting to assess heart
viability.
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Methods
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Human Animal Care
All animals were treated in accordance with
the Principles of
Laboratory
Animal Care formulated by the National Society for Medical
Research
and the Guide for the Care and Use of Laboratory Animals
prepared
by the National Academy of Sciences and published by the NIH
(NIH
Publication No. 85-23, revised 1985).
Heart Harvesting
Adult pigs of both sexes weighing 25 to 30
kg were anesthetized
with ketamine hydrochloride (0.33 mg/kg) for induction and a mixture of
fentanyl (0.04 mg/kg) and Pavulon (0.30 mg/kg) for maintenance, as
described previously.15 Animals were artificially
ventilated, and heparin was given immediately (1000 IU/kg IV). Pigs
were exsanguinated and randomized into five groups: group I (n=6)
received 0 minute of in situ warm ischemia; group II (n=6), 10 minutes
warm ischemia; group III (n=6), 20 minutes warm ischemia; group IV
(n=6), 30 minutes warm ischemia; and group V (n=6), 60 minutes
warm
ischemia. A left thoracotomy was performed quickly, and the hearts were
removed and washed in St Thomas's cardioplegic solution (Aguettant
Laboratory) at 4°C.
Assessment of Heart Viability During Cardioplegia
The
ascending aorta was immediately cannulated, and coronary
arteries were flushed for 3 minutes with the same hypothermic solution
at a pressure of 60 cm H2O. Initial coronary flow was
expressed in milliliters per minute per 100 grams of myocardial tissue.
To assess edema, the hearts were weighed before and after flushing. The
ionic composition (Na+, Ca++, and
K+) of the coronary sinus effluent was analyzed in hearts
in groups I and V. Sodium and potassium were measured with an
ion-selective electrode module (614 CIBA Corning), whereas calcium was
measured spectrophotometrically at 550 nm, as described by Kessler and
Wolfman.16
Left ventricular biopsies were performed, and
myocardial samples were
frozen in liquid nitrogen for subsequent adenine nucleotide
measurements, as described.17 Briefly, frozen biopsies
were lyophylized, weighed, crushed to powder, and homogenized with 0.6N
perchloric acid (7 mL/g frozen tissue). The supernatant was neutralized
with 1 mol/L KOH. The neutralized extract was freed of potassium
perchlorate by centrifugation (15 minutes at 1000g and 4°C). Adenine
nucleotides (ATP, ADP, and AMP) were separated by high-performance
liquid chromatography, as described,17 and an energetic
index was calculated according to the formula
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Functional Reperfusion
After 2 hours of cold storage in St
Thomas's solution, a latex
balloon was introduced into the left ventricle and connected to a
pressure transducer with a recorder. Hearts were then reperfused with
600 mL conserved, heparinized whole blood at 38°C. The initial pH of
the solution was 7.2 to 7.4 after equilibrium with a mixture of 95%
O2/5% CO2 and 20 mL
Na2CO3 at 4.2%. Perfusion pressure was
gradually increased from 2.9 KPa (30 cm H2O) at the
beginning of reperfusion to 4.9 KPa (50 cm H2O) at 20 to 30
minutes. At baseline and after 15 and 30 minutes of reperfusion, the
functional state of the heart was evaluated by measuring left
ventricular developed pressure (LVDP).
Statistical Analysis
Results are expressed as the
mean±SD. Groups of pigs were
compared by ANOVA (Fisher's test). Difference was considered
significant when the P value was <.05. Correlation
significance was obtained with the Fisher-Yates statistical
tables.
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Results
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Effect of In Situ Warm Ischemia on Myocardial Edema
Statistical comparisons were performed among all groups
(F=70.89,
P=.0001).
During the cardioplegic flush, there was no weight
increase
in group I hearts. In hearts in groups II, III, and IV, there
was
a mild, nonsignificant weight increase (4.1±0.8%, 3.1±2.8%,
and
3.2±1.5%,
respectively). In contrast, there was a significant weight
increase
(37±11%,
P<.001, Fig 1
), in
hearts in group V.
Effect of In Situ Warm Ischemia on Initial Coronary Flow
During the cardioplegic flush, mean coronary artery flow in the
control hearts (group I) was 70±14 mL/min per 100 grams myocardial
tissue. Results in all groups were different (F=21.85,
P=.0001). A decrease in coronary flow was observed in groups
II through V: group II, 52±9 mL/min per 100 grams (P<.01
versus group I); group III, 41±16 mL/min per 100 grams; group IV,
25±11 mL/min per 100 grams; and group V, 23±5 mL/min per 100
grams
(P<.001 versus group I). Differences in hearts in groups II
and III were also statistically significant in those in groups IV and V
(Fig 2).
Effect of In Situ Warm Ischemia on the Ionic Composition of
Coronary Sinus Effluent
During the cardioplegic flush, coronary sinus
effluents of
each heart in groups I and V were collected and their electrolyte
contents (Na+, K+, and
Ca++) were measured and compared (F=26.27,
P=.0001). Ionic concentrations of the input medium (St
Thomas's solution) were substracted from those of the coronary sinus.
Thus, when electrolytes were released from cardiomyocytes, the
concentration was above the baseline, whereas when electrolytes were
removed from the medium by cardiomyocytes, the concentration was below
the baseline (Fig 3). Significant removal of calcium and
sodium was observed in hearts in group V compared with group I
(-0.05±0.02 mmol/L versus +0.11±0.02, respectively,
for calcium,
P<.001, and -7.74±3 mmol/L versus
+0.88±0.7,
respectively, for sodium, P<.01), whereas we found no
significant difference between groups with regard to potassium:
-0.41±0.3 versus -1.15±0.09 mmol/L.
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Figure 3. Bar graph showing electrolyte exchanges
(CA2+, Na+, and K+)
during cardioplegia in hearts in the control group (Control) and in
hearts that underwent 60 minutes of in situ warm ischemia (60 min WI).
See text for explanations. Values shown are the mean±SEE of nine
values (n=18 total hearts, 9 per group). *P<.05,
**P<.01, ***P<.001.
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Relation With Initial Coronary Flow
The energetic index was
positively correlated with the initial
coronary flow during cardioplegia (r=.84,
P<.001, Fig 4). A significant correlation
was also found between the initial coronary flow measured during
cardioplegic flushing and the maximal LVDP (Fig 5)
assessed during reperfusion (r=.90,
P<.001).
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Figure 4. Scatterplot showing relation between coronary flow
measured during cardioplegic flushing and energetic index. The decrease
in the energetic index was correlated with the decrease in coronary
flow (r=.84, P<.001).
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Figure 5. Scatterplot showing relation between coronary flow
measured during cardioplegic flushing and left ventricular developed
pressure at reperfusion. A good correlation was established
(r=.90, P<.001).
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Discussion
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The only test now available for assessing myocardial viability
for
transplantation is transplantation itself. Thus, harvesting
and
preservation must be done as quickly as possible to avoid
myocardial
injury during cold ischemia. Surgical teams must
work according to
emergency procedures. Moreover, in the absence
of accurate criteria of
viability, it is accepted that the heart
must not be transplanted
beyond 4 to 6 hours of cold ischemia.
Finally, despite these
precautions, some hearts considered viable
before harvesting show
irreversible failure after transplantation.
Obviously, there is a need
for a reliable test of heart viability
before transplantation to help
to reduce the incidence of graft
failure and to increase the number of
hearts available for transplantation.
Furthermore, the ability to
evaluate graft viability would permit
hearts to be preserved beyond the
present limit of time.
We previously developed an experimental cardiac hypothermic
preservation and biophysical data recorder system19 that
enables us to measure coronary artery flow, myocardial perfusion flow,
and edema formation in a real-time manner. Our previous data suggested
that coronary flow and edema may be good indicators of heart viability.
In the present study, edema formation during cardioplegia was not
correlated with duration of warm ischemia. Except in the hearts in
group V, which underwent 60 minutes of in situ warm ischemia, no weight
gain was observed among the groups, despite an evident myocardial
injury. We conclude that edema evaluation during cardioplegic flush is
not a reliable index of viability in this model. In contrast, the
initial coronary flow correlated well and inversely with the increase
in in situ warm ischemia. Coronary flow and coronary resistance are two
correlated parameters, expressed as follows:
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where CR is the coronary resistance; PP, the perfusion pressure;
Wt, the heart weight; and CF, the coronary flow. Because the coronary
perfusion pressure was fixed at 60 cm H2O and the heart
weight was stable (except in group V), coronary flow reflected coronary
artery resistance. If the whole coronary system is considered a unique
blood vessel, then coronary resistance could be expressed with the
Poisseuille law as follows:
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where µ is the viscosity of the cardioplegic medium and l and r
are the length and radius of the vessel, respectively. Two parameters
could vary: the length could decrease when arteriovenous shunt
occurred, and the radius could increase with arterial vasomotion.
Therefore, the increase in coronary resistance involved a
vasoconstriction phenomenon. We thus hypothesize that one of the main
consequences of warm ischemia is coronary artery wall injury and that
initial coronary flow measurement may be a good predictor of severity
of heart injury. As a matter of fact, we found a strong positive
correlation between LVDP during reperfusion and coronary flow during
cardioplegic flush. However, warm ischemia may also induce depletion of
high-energy compounds, and the myocardial energetic index was strongly
correlated with initial coronary flow. Thus, initial coronary flow may
be used as an indicator of myocardial energy–reserve status. Finally,
electrolyte exchanges in myocardial tissue were shown to be altered by
warm ischemia. A significant calcium accumulation occurred in the
cardiomyocytes subjected to 60 minutes of ischemia (group V), which
suggests formation of incipient stone heart.20 In
addition, our data indicate significant sodium retention in the
ischemic (group), which is in accordance with the measured weight
increase that is probably due to water accumulation. Finally, there was
also a significant difference among groups in potassium concentration,
suggesting potassium loss and cardiomyocyte injury.
Any technique aimed to evaluate heart viability for human surgery must
be simple, safe, rapid, reliable, and easy to perform in a clinical
setting. In such a context, biochemical evaluations, such as energetic
compound measurements, are very time consuming and therefore
unsuitable. In contrast, measurement of coronary flow at the time of
cardioplegic flush lasts 3 minutes but requires only aortic cannulation
and careful weighing of the heart and coronary effluents. This test
could be used without complex and costly apparatus. Obviously, these
data have to be confirmed on an ischemic pig heart model to include
orthotopic transplantation and evaluation of the in situ working heart.
We also plan to evaluate the viability of cadaveric beating hearts that
are not considered suitable donor candidates under the current rules of
human grafting.
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Conclusion
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A 3-minute coronary artery flow measurement during cardioplegic
flush
after heart harvesting may be a reliable predictor of heart
viability
and may permit procurement and transplantation of hearts now
considered
unsuitable for transplantation. A better estimate of initial
graft
status may help to improve prognosis.
Received September 15, 1994;
accepted November 25, 1994.
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References
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-
Fahy GM. Viability assessment. In: Karow AM, Pegg DE,
eds. Organ Preservation for Transplantation. New York, NY:
Dekker; 1981;53-73.
-
Proctor E, Matthews G, Archibald J. Acute orthotopic
transplantation of hearts stored for 72 hours. Thorax. 1971;26:99-101. [Medline]
[Order article via Infotrieve]
-
Suros J, Woods JE. Twenty-hour preservation of the canine
heart. J Surg Res. 1974;16:672-678. [Medline]
[Order article via Infotrieve]
-
Watson DC, Gregg DL, Rhodes GR. Survival after orthotopic
transplantation of hearts preserved for 48 hours. Surg
Forum. 1976;255-257.
-
Rijk GL, Foegh M, Ramwell PW, et al. Long-term myocardial
preservation: thromboxane production and coronary resistance. J
Surg Res. 1983;35:417-420. [Medline]
[Order article via Infotrieve]
-
Vanhaecke J, Flameng W, Bargers M, et al. Evidence for
decreased coronary flow reserve in viable postischemic myocardium.
Circ Res. 1990;67:1201-1210. [Abstract/Free Full Text]
-
Magovern GJ, Bolling SF, Casale AS, Bulkley BH, Gardner TJ.
The mechanism of mannitol in reducing ischemic injury: hyperosmolarity
or hydroxyl scavenger. Circulation. 1984;70:91-94.
-
Guerraty A, Alicizatos P, Warner M, Hess M, Allen L, Lower
RR. Successful orthotopic canine heart transplantation after 24 hours
of in vitro preservation. J Thorac Cardiovasc Surg. 1981;82:531-537. [Abstract]
-
Wicomb W, Boyd ST, Cooper DKC, Rose AG, Barnard CN. Ex
vivo functional evaluation of pig hearts subjected to 24 hours
preservation by hypothermic perfusion. South Med J. 1981;60:245-248.
-
Cooper DKC, Wicomb WN, Barnard CN. Storage of the donor heart
by a portable hypothermic perfusion system: experimental development
and clinical experience. Heart Transplantation. 1983;2:104-110.
-
Bethencourt DM, Laks H. Importance of edema and compliance
changes during 24 hours of preservation of the dog heart. J
Thorac Cardiovasc Surg. 1981;81:440-449. [Abstract]
-
Weng ZC, Nicolosi AC, Detwiler PW, et al. Effects of
crystalloid, blood and University of Wisconsin perfusates on weight,
water content and left ventricular compliance in an edema-prone,
isolated porcine heart model. J Thorac Cardiovasc Surg. 1992;103:504-513. [Abstract]
-
Stringham JC, Southard JH, Hegge J, et al. Limitations of
heart preservation by cold storage. Transplant. 1992;53:287-294. [Medline]
[Order article via Infotrieve]
-
Kresh JY, Cobanoglu MA, Brockman SK. The intramyocardial
pressure: a parametre of heart contractility. Heart
Preservation. 1985;4:241-246.
-
Ferrera R, Marcsek P, Larèse A, Girard C, Fussellier M,
Dittmar A, Dureau G. Comparison of continuous microperfusion and cold
storage for pig heart preservation. J Heart Lung Transplant. 1993;12:463-469. [Medline]
[Order article via Infotrieve]
-
Kessler G, Wolfman M. An automated procedure for the
determination of calcium and phosphorus. Clin Chem. 1964;10:686-703. [Abstract]
-
Ferrera R, Larèse A, Marcsek P, Guidollet J, Verdys M,
Dittmar A, Dureau G. Comparison of different techniques of hypothermic
pig heart preservation. Ann Thorac Surg. 1994. In press.
-
Atkinson DE. The energy charge of the adenylate pool as a
regulatory parameter: interaction with feedback modifiers.
Biochemistry. 1968;7:4030-4034. [Medline]
[Order article via Infotrieve]
-
Ferrera R, Marcsek P, Jossinet J, Delhomme G, Larèse A,
Dureau G, Dittmar A. Tissular biophysic and thermic parameters study
during cardiac graft hypothermic preservation. Innov Tech Biol
Med. 1991;12:502-516.
-
Dureau G, Ferrera R. Principles of organ perfusion and
reperfusion with special reference to the heart. In: Libbey J, ed.
Research in Organ Transplantation. 1994. In
press.
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Abstract
Introduction
