TUESDAY MORNING,
APRIL 28, 1992
7:30 a.m. FORUM SESSION I - Cardiac Surgery - Los
Angeles Ballroom
F1. Pathogenesis of Ischemic Mitral Insufficiency
MARIO R. LLANERAS, M.D.*,
STEPHEN W. DOWNING, M.D.*, JOAO A. C. LIMA,
M.D.*,
MICHAEL L. NANCE, M.D.*, RADU C. DEAC, M.D.,
PHILIP L. LINDEN, B.A.* and
L. HENRY EDMUNDS, JR., M.D.
Philadelphia, Pennsylvania
We hypothesized that the combination of a moderate sized posterior
in-farct and infarction of the posteromedial papillary muscle (PPM) were
required to cause ischemic mitral regurgitation (MR); neither condition alone
would cause MR. In 72 sheep (19 slaughterhosue hearts, 25 acute experiments and
28 chronic experiments) the coronary artery anatomy was detailed by gross
inspection, dye injections in cadaveric hearts, vital staining and coronary
angiography. Ligation of the first and second marginal (OM1 & OM2) branches
of the left circumflex artery consistently infarcted 23 ± 3.3% (by planimetry)
of the left ventricular mass. Color flow doppler performed in-traoperatively in
12 sheep with the OM1/OM2 infarct, revealed no appreciable MR up to eight weeks
postinfarct despite dilatation on the left ventricle (LV).
Ligation of
the second and third (OM2 & OM3) marginal branches, in 16 sheep, infarcted
21.4 ± 4.0% of the LV mass and completely infarcted the PPM in all but two
animals. Wall thickness at the level of the PPM is 1.6 ± 0.2 cm before
infarction and decreases to 0.4 ± 0.1 cm 8 weeks after infarction. Left
ventriculography and intraoperative color flow echocardiography demonstrated MR
which progressed in severity following infarction. Eight sheep have been
followed serially for 8 weeks; two had incompletely infarcted PPM and did not
develop IMR. Three other sheep developed severe mitral regurgitation immediately
after infarction and died early. Five sheep with MR have not reached 8 weeks
(cf. graph). The consistency of coronary arterial anatomy in sheep and lack of
collaterals result in anatomically uniform infarcts between sheep and
predictable ischemic MR. The data show that a 23% posterior infarction sparing
the PPM or an infarction of the PPM alone does not produce MR. Both conditions
must be present. This preparation provides a reproducible model of ischemic MR
and offers a means to devise repairs based on the pathophysiology of the
disease.
*By Invitation
F2. Very
Small Diameter Polyurethane Vascular Prostheses With Rapid Endothelialization
for Coronary Artery Bypass Grafting
TAKAFUMI OKOSHI, M.D.*, GIORGIO SOLDANI,
Sc.D.*
MOSES GODDARD, M.D.* and
PIERRE M. GALLETTI, M.D.*
Providence, Rhode Island
Sponsored by: Karl E. Karlson, M.D.,
Providence, Rhode Island
The growing incidence of "redo" coronary
artery bypass grafting (CABG) calls for the development of satisfactory
prosthetic substitutes for the internal mammary artery or the saphenous vein.
Porous non-woven tubular fabrics provide one approach to that challenge. Two
types of spongy polyurethane-polydimethylsiloxane (Cardiothane 51, Kontron
Instruments, Inc.) vascular grafts with an internal diameter (ID) of 1.5 mm
were fabricated by a spray, phase-inversion technique. Low porosity grafts
(LPG) with hydraulic permeability (HP) of 2.7 ± 0.4 ml/min.cm2, and
medium porosity grafts (MPG) with HP of 39 ± 8 ml/min/cm2, displayed
good handling properties and suturability. Twelve straight LPG, seventeen
straight MPG (1.5 - 2.0 cm in length) and one loop MPG (10 cm in length) were
implanted by the same surgeon end-to-end in the infrarenal aorta of 30 male
Sprague-Dawley rats. No antithrombogenic agents were administered pre- or
postoperatively. At 3 months postimplantation, patency was 8% for LPG (1/12)
and 76% for the straight MPG (13/17). The loop MPG was also patent. The sole
patent LPG showed neointimal hyperplasia and incomplete endothelialization. All
but one of the patent straight MPG showed a glistening and transparent
neoin-tima with complete endothelialization. The loop MPG displayed
endothelialization from each anastomosis and in many islands in the middle
portion of the graft, totalling 47% of the luminal surface by morphometric
analysis. Thick mural thrombus, anastomotic hyperplasia, or aneurysm formation
were not observed in patent MPG. These data indicate that in the rat aortic
replacement model it is possible to achieve patency and a high degree of
endothelialization in very small diameter prostheses of appropriate porosity.
This may open an avenue to the use of synthetic grafts in aorto-coronary bypass
surgery.
*By Invitation
F3. Cardiopulmonary Dysfunction Produced by
Initiating Reoxygenation on Cardiopulmonary Bypass in Immature Hypoxemic
Piglets: Prevention by Intravenous Metabolic Treatment
GEORG MATHEIS, M.D.* GERALD D. BUCKBERG, M.D.,
DENIS B. TIXIER, M.D.*, HELEN H. YOUNG, Ph.D.*
and MICHAEL P. SHERMAN, M.D.*
Los Angeles, California
This study tests the hypothesis that reoxygenation
injury is produced when Cardiopulmonary bypass (CPB) is initiated in immature
hypoxemic piglets, and causes cardiopulmonary dysfunction that can be avoided
by intravenous metabolic treatment before and during CPB.
Of eighteen immature Yorkshire-Duroc piglets
(<3 weeks old) six were anesthetized, instrumented and observed over 5 hours
(control). Twelve piglets underwent up to 2 hours of hypoxemia (paO2
= 20-30 mmHg) before initiation of reoxygenation on CPB. Six received an
intravenous metabolic infusate (mercaptopropionyl glycine, catalase, aspartate,
glutamate, glucose/insulin) which was started before and continued during CPB.
Hypoxia produced an initial hyperdynamic response
(39% increased cardiac index) followed by progressive hemodynamic
deterioration. This required premature initiation of bypass in 8 out of 12
hypoxemic piglets (67%).
|
|
Control
|
NORX
|
Intravenous Rx
|
|
Stroke Work Index
@ LAP 8 mmHg
|
1.08 ± 0.16
|
0.66 ± 0.06*
|
1.07 ±0.09
|
|
Conjugated Dienes
(A233
nm/mg lipid)
|
0.73 ± 0.10
|
1.31 ± 0.14*
|
1.01 ± 0.09
|
|
Pulmonary Vascular Resistance Index
|
83 ± 12
|
294 ± 34*
|
190 ± 27
|
|
Static Lung Compliance
(% Control)
|
100 ± 8%
|
78 ± 4%*
|
105 ± 21%
|
|
a/A pO2 Ratio #
|
0.66 ± 0.04
|
0.33 ± 0.06*
|
0.62 ± 0.07
|
(values
are mean ± SEM,* = p<0.05 vs. Control, ANOVA, ^arterial/alveolar pO, Ratio)
Reoxygenation induced injury (assessed 30 minutes
after CPB) was characterized by reduced stroke work index, increased myocardial
lipid peroxidation (conjugated dienes), increased pulmonary vascular resistance
index, impaired statis lung compliance, and decreased a/A pd ratio. These
reoxygenation changes were avoided by intravenous metabolic treatment.
We conclude that the reoxygenation of immature
hypoxemic piglets by initiating
CPB results in cardiopulmonary dysfunction which may increase vulnerability to
subsequent ischemia (i.e. aortic crossclamping) and is preventable by
intravenous metabolic treatment before and during CPB needed for cardiac
repair.
*By Invitation
F4. Normocalcemic Blood or Crystalloid
Cardioplegia Provides Superior Neonatal Myocardial Protection Over Low Calcium
Cardioplegia
JEFFREY M. PEARL, M.D.*, HILLEL LAKS, M.D.,
DAVIS C. DRINKWATER, M.D.*,
AVEDIS MENESHIAN, B.S.* and PAULA. CHANG*
Los Angeles, California
Although standard blood cardioplegia provides good
myocardial protection for adult cardiac surgery, protection of the cyanotic,
immature myocardium remains suboptimal. Calcium, which has been implicated in
reperfusion injury and the development of "stone heart" in mature myocardium,
is routinely removed from standard cardioplegia solutions. Immature, neonatal
myocardium has lower intracellular calcium stores and is more reliant on
extracellular calcium for contraction, and for maintenance of the glycocalyx
membrane. In order to determine if normocalcemic cardioplegia would result in
improved cardiac function in the neonatal heart, we conducted a series of
experiments using an isolated, blood perfused working heart model. Neonatal
piglet hearts (24-48 hours) were excised without intervening ischemia and
placed directly on a blood perfused circuit. Baseline stroke-work index (SWI)
was assessed. Hearts were then arrested with cold cardioplegia delivered at 45
mmHg for 2 minutes; Group I = low-Ca + 2 Blood CP (Ca = 0.6 mmol/1); Group II =
normal-Ca + 2 blood cardioplegia (Ca=1.1 mmol/1); Group III = University of
Wisconsin (UW) solution; and Group IV = UW with added calcium (Ca= 1.0 mmol/1).
Each group consisted of 8 hearts. Cardioplegia was administered every 20
minutes for 2 hours and topical hypothermia was employed. Hearts were then
reperfused with warm whole blood. Functional recovery, expressed as percent of
control SWI, was determined 60 minutes following reperfusion.
Hearts preserved with normocalcemic CP (Groups II
and IV) had complete (100%) functional recovery at 60 minutes, whereas hearts
preserved with low-calcium CP (Groups I
and III) had only 80% and 58% recovery at LAP of 9 mmHg, respectively. Percent
recovery decreased further at higher left atrial pressures in the low calcium
groups, indicating diastolic dysfunction. Electronmicrographs taken 1 hour
after reperfusion showed minimal edema and only mild myofibrillar changes, and
were identical in both the low calcium and normal calcium groups. Conclusion:
100% functional recovery is possible in immature myocardium when calcium is
added to either blood or crystalloid cardioplegia. The addition of calcium does
not result in ultrastructural damage ("calcium paradox") and results in
superior functional recovery.
By Invitation
F5. Effect of Calcium and Preischemic Hypothermia
on Recovery of Myocardial Function After Cardioplegic Ischemia in Neonatal
Lambs
MITSURU AOKI, M.D.*, JOHN E. MAYER, JR.,
M.D.,
FUMIKAZU NOMURA, M.D.* and
HIROAKI KAWATA, M.D.*
Boston, Massachusetts
Most neonatal cardiac operations are peformed
at deep hypothermia, but controversy exists over the danger of hypothermia
prior to cardioplegic arrest. Hypothermia can cause myocyte Ca accumulation
experimentally and has been noted to result in reduced postischemic recovery in
some experimental and clinical reports. Preischemic hypothermia is routinely
used in other centers with good results. To explore this discrepancy we
evaluated the effects of preischemic ionized (i) Ca concentration and
temperature on outcome after 2 hrs and 15°C cardioplegia-protected ischemia in
38 isolated, blood perfused neonatal lamb hearts. LV maximal developed pressure
(DP), dP/dt, -dP/dt, coronary blood flow (CBF), and oxygen consumption (MVO2)
were measured before and 30 and 60 minutes after 2 hours of ischemia. After
baseline measurements, hearts were perfusion-cooled (groups B, C, and D) for 10
minutes to 17 °C and then arrested with cold (4°C) St. Thomas cardioplegia.
Group A had 10 minutes of normothermic perfusion after baseline
measurements, then were arrested with the cold cardioplegia. Group B had
cooling normal iCa. Group C had citrate (Cit) added as cooling was started to
low iCa and iCa was not normalized until 15 minutes into reperfusion. Group D
received citrate plus Ca to give normal iCa during cooling. Results are given
as % recovery of baseline except iCa (nM/1).* =p<0.05 vs groups B and D.
|
|
|
Pre
|
Cooling
|
30
minutes reperfusion
|
60
minutes reperfusion
|
|
Group
|
n
|
iCa
|
iCa
|
iCa
|
DP
|
dP/dt
|
-dP/dt
|
DP
|
dP/dt
|
-dP/dt
|
|
A
(No Cooling)
|
8
|
0.99
|
-
|
1.00
|
92.8*
|
86.0*
|
76.2*
|
85.7*
|
72.1*
|
64.0
|
|
B
(Cooling)
|
8
|
1.06
|
1.06
|
1.06
|
79.0
|
69.9
|
66.8
|
72.0
|
60.0
|
57.2
|
|
C (Cooling
+ Cit)
|
8
|
1.06
|
0.26*
|
1.10
|
91.6*
|
84.7*
|
77.8*
|
86.5*
|
74.8*
|
71.3*
|
|
D
(Cooling + Cit + Ca
|
8
|
1.02
|
1.03
|
1.07
|
67.6
|
62.2
|
54.7
|
59.7
|
51.9
|
46.6
|
MVO2 per beat significantly increased while the coronary
blood flow decreased during preischemic cooling (p<0.05) in all groups. CBF
was higher in Group C than in other groups during both pre and postischemia as
long as iCa was low (p<0.05).
These data suggest that preischemic
hypothermia results in reduced postischemic recovery of function than simultaneous
induction of cardioplegia and hypothermia. Low iCa during preischemic
hypothermia and early reperfusion offsets these effects. Therefore, careful
attention to both temperature and iCa prior to ischemia are important in the
outcome after ischemia in neonatal hearts.
*By Invitation
F6. Temporary Leukocyte
Depletion Reduces Ventricular Dysfunction During Prolonged Postischemic
Reperfusion
IAN C. WILSON, MB, ChB*, TIMOTHY J. GARDNER,
M.D.,
JOSEPH M. DiNATALE, B.S.*,
A. MARC GILLINOV, M.D.*, WILLIAM E. CURTIS,
M.D.*
and DUKE E. CAMERON, M.D.*
Baltimore, Maryland
Previous experiments in our laboratory have
demonstrated that leukocyte depletion improves early postischemic
ventricular performance in a neonatal model of global myocardial ischemia.
However, the rate at which leukocytes return to the circulation after
cardiopulmonary bypass (CPB), their possible late accumulation in the
myocardium and their subsequent effect on the functional recovery of left
ventricle is not known.
The present study examined the effect of leukocyte
depletion on myocardial performance during the 6 hour period post CPB in an in
situ, in vivo porcine model of neonatal cardiac surgery. Median sternotomy
was performed on thirteen 3-5 day old piglets, 6 controls and 7 leukocyte
depleted animals (LD), and left ventricular (LV) short-axis sonomicrometry
crystals and an in-traventricular micromanometer positioned. Piglets were
cooled to 22 °C prior to 90 minutes hypothermic ischemia after a single dose of
cold crystalloid car-dioplegia. Mechanical leukocyte depletion was achieved
using Pall RC100 filters. Granulocyte counts in the initial coronary
reperfusate were reduced to 0.8% of controls (2±1 cells/ml, mean±SEM,
p<0.001). However, circulating granulocyte counts progressively increased
throughout the period of myocardial reperfusion reaching 66% of controls
(874±356/ml) after 6 hours (p<0.3). Control piglets demonstrated an
immediate reduction in postischemic left ventricular performance (measured
by preload recruitable stroke work, PRSW) to 87 ± 6% baseline. PRSW further
declined to a nadir of 73 ± 8% at 4 hours before improving to 86 ± 6% 6 hours
postoperatively. In contrast, LV performance in LD animals were 94 ±6% baseline
immediately post CPB and did not decline throughout the period of observation,
remaining 98 ± 5% and 98 ± 4% baseline at 4 and 6 hours, respectively
(p<0.02). Left ventricular systolic function (measured by
end-systolic pressure-volume relationship) and ventricular compliance similarly
were better preserved in the LD group throughout the postoperative period
(p<0.05 and p<0.04, respectively). This improvement in postischecmic
ventricular function was associated with decreased myocardial water content at
6 hours (79.6 ± 0.9%) compared to the control group (80.9 ± 0.8%, p<0.02),
and with reduced tissue myeloperoxidase concentration (46% of controls,p<0.05),
representing less myocardial leukocyte accumulation.
These data show that leukocyte depletion
during initial reperfusion reduces myocardial leukocyte accumulation and
results in sustained improvement of postischemic LV function. Temporary
manipulation of the leukocyte population during cardiopulmonary bypass can
reduce myocardial injury and improve myocardial protection following prolonged
reperfusion despite rapid return of granulocytes to the circulation within 6
hours.
*By Invitation
F7. Alternative Methods of Retrograde Cardioplegia
Delivery: Effects on Preservation of the Ischemic Left Ventricle After Acute
Coronary Artery Occlusion and Reperfusion
JAMES T. DIEHL, M.D.* MICHAEL PONTORIERO, M.D.*,
RAYMOND CONNOLLY, Ph.D.*
STEVEN SCHWARTZ, M.D.* and
RICHARD J. CLEVELAND, M.D.
Boston, Massachusetts
Myocardial protection may be enhanced by
altering the flow (intermittent vs continuous) and temperature (cold vs warm)
of retrograde blood car-dioplegia. 24 dogs were randomized into 4 cardioplegia
groups (n = 6): Group I - intermittent cold antegrade, Group II - intermittent
cold retrograde, Group III - continuous warm retrograde, and Group IV -
continuous cold retrograde. Preservation was assessed with a model of left
ventricular ischemia and reperfusion induced by acute occlusion of the LAD.
Functional parameters were collected at baseline, at 60 minutes of LAD
occlusion (ischemia), and following reperfusion. All dogs were maintained
normother-mic during cardiopulmonary bypass (CPB) and all data was collected
off CPB. Regional and global LV function is reported as the load independent
slope (E max) of fiber segment and minor LV axis dimension vs LV end systolic
pressure respectively. Group I demonstrated no recovery of global LV function
(#).Recovery of global LV function was similar for Grp II, III, and IV
(*). Regional LV function demonstrated significant functional recovery only for
Group IV, continuous cold retrograde cardioplegia (**). 2-D echo wall motion
studies confirm this data.
|
E max
|
GrpI(n = 6)
|
GrpII(n = 6)
|
GrpIII (n = 6)
|
GrpIV (n = 6)
|
|
Global Ischemia
|
18±2
|
22±2
|
20±3
|
18±2
|
|
Post-reperfusion
|
17±5#
|
36 ±3*
|
38 ±2*
|
38 ±5*
|
|
Regional
|
|
|
|
|
|
Ischemia
|
49 ±10
|
47 ±10
|
51±4
|
43 ±6
|
|
Post- reperfusion
|
48 ±26
|
72 ±48
|
112±29
|
129 ±28**
|
|
# NS vs ischemia
|
|
*P<0.05 vs
ischemia and vsGrpI
post-reperfusion
|
|
"P<0.05 vsGrpIV ischemia - All data expressed as mean ± SEM
|
Conclusions:
1. Retrograde cardioplegia provides superior
global LV preservation during ischemia when compared with antegrade
cardioplegia.
2. Preservation of regional myocardium beyond
an occluded coronary artery is best achieved with cold continuous retrograde
cardioplegia.
*By Invitation
F8. Detrimental Effects of Interrupting Warm Blood
Cardioplegia During Coronary Revascularization
HIROSHI MATSUURA, M.D.*, HAROLD L. LAZAR,
M.D.,
XI MING YANG, M.D.*, SAMUEL RIVERS, B.S.*,
PATRICK R. TRAENOR, CCP* and
RICHARD J. SHEMIN, M.D.
Boston, Massachusetts
Warm Blood Cardioplegia (WBC) has emerged as an
alternative method of myocardial protection to Cold Blood Cardioplegia (CBC).
However, the continuous infusion of blood required in this technique may
obscure the operative field necessitating that the WBC be interrupted. The
effects of interrupting WBC during coronary revascularization are unknown. This
experimental study was therefore undertaken to determine whether interrupting
WBC during coronary revascularization will result in increased myocardial
damage.
In 30 adult pigs, the second and third
diagonal vessels were occluded with snares just beyond the LAD for 1 ½ hours. All animals were then placed on
cardiopulmonary bypass and underwent 45 minutes of cardioplegic arrest.
Following aortic unclamping, the coronary snares were released and all hearts
were reperfused for 3 hours. During the period of cardioplegic arrest, 10 pigs
received intermittent, antegrade/retrograde CBC (4°C), 10 animals received
continuous, retrograde WBC (37°C) at 100 ml/min; and 10 animals received
continuous, retrograde WBC but had the infusion stopped for three 7 minute
periods during the 45 minute crossclamp period. The effectiveness of myocardial
protection in the area at risk was assessed by myocardial pH measured during
cardioplegic arrest using tissue pH probes, Wall Motion Scores (WMS) using 2-D
echo (4 = normal to -1 = dyskinesia), and the Area of Necrosis/Area of Risk
(AN/AR) using histochemical staining. Results are Mean±SE;*p<.05 from
Antegrade/Retrograde CBC; +p<.05 from Retrograde WBC.
|
|
Antegrade/Retrograde
|
Retrograde
|
Interrupted Retrograde
|
|
|
CBC
|
WBC
|
WBC
|
|
pH
|
6.98 ± .17
|
6.45 ± .12*
|
6.20 ± .16
|
|
WMS
|
3.3 ± .4
|
2.8 ± .4
|
2.06 ± .30*
|
|
AN/AR (%)
|
21 ± 2
|
25 ± 2
|
38 ± 5+*
|
Interrupting Retrograde WBC resulted in more tissue
acidosis during acrioplegic arrest, lower wall motion scores, and increased
tissue necrosis. We conclude that interrupting WBC during coronary
revascularization diminishes the effectiveness of WBC and results in increased
ischemic damage.
*By Invitation
F9. Complete Prevention of Myocardial Stunning,
Low-Reflow and Edema After Heart Transplantation by Blocking Leukocyte Adhesion
Molecule During Reperfusion
JOHN G. BYRNE, M.D.*, LAWRENCE H. COHN, M.D.,
WENDEL J. SMITH, M.D.*, MICHAEL P. MURPHY,
M.D.*,
GREGORY S. COUPER, M.D.* and
ROBERT F. APPLEYARD, Ph.D.*
Boston, Massachusetts
Following heart preservation and
transplantation, reperfusion-induced microvascular inflammation with release of
leukocyte-derived toxic mediators (oxygen free radicals, enzymes) has been
suggested as an underlying mechanism leading to edema, "low-reflow" and
subsequent diastolic dysfunction ("diastolic stunning"). For lekocytes
to mediate inflammation and release their toxic mediators they must first
adhere to either each other or to the endothelium. We therefore hypothesized
that preventing leukocyte adhesion, by blocking leukocyte membrane
adhesion molecule CD18, would reduce myocardial inflammation and edema and
improve reflow and diastolic function after heart preservation and
transplantation.
Methods: After cardioplegia and insertion of an LV balloon, rabbit hearts were
heterotopically transplanted into recipient rabbits either immediately
(Immediate, n = 12) or after preservation in 4°C saline (3 hrs ischemia,
n = 23). Recipients of preserved hearts received, 45 min before
reperfusion, either IV saline (Placebo, n = 13) or IV anti-CD18
monoclonal antibody R15.7 (2 mg/Kg) (Anti-CD18, n =10). During 3
hours reperfusion the slope of the end-systolic pressure-volume relation
(Emax), the exponential elastic coefficient of the end-diastolic
pressure-volume relation (β), the unstressed ventricular volume (V0)
and the time constant of the exponential LV pressure fall after dP/dtmin
(τ) were serially measured. Myocardial blood flow was measured
with microspheres from which coronary vascular resistance (CVR) was calculated.
After explantation the degree of myocardial inflammation, estimated by tissue
leukocyte sequestration (Myeloperoxidase assay, MPO), and myocardial water
content (%H2O) were determined.
|
|
|
Emax
|
b
|
V0
|
t
|
CVR
|
MPO
|
%H2O
|
|
Group
|
n
|
(mmHg/ml)
|
|
(ml)
|
(msec)
|
U/g
|
(mU/g)
|
|
|
Immediate
|
12
|
63. 3 ± 2.7
|
3.4 ± 0.3
|
0.3 ± 0.2
|
37.9 ± 3.8
|
70.5 ± 10.6
|
1712 ± 552
|
75.6 ± 1.3
|
|
Placebo
|
13
|
67.6 ± 3.1
|
3.1 ± 0.3
|
-0.5 ± 0.3
|
157.7 ± 4.4*
|
1 15.5 ± 13.4#
|
3380 ± 456#
|
79.8 ± 0.4#
|
|
Anti-CD18
|
10
|
57.6 ± 3.6
|
4.3 ± 0.3
|
0.5 ± 0.3
|
32.7 ± 5.0
|
64.8 ± 4.5
|
1100 ± 308
|
75.2 ± 1.7
|
Values: Mean ± SEM;*p<0.01 vs Immediate; p<0.01 vs Placebo;
#p<0.05 vs Immediate; p<0.05 vs Placebo (ANOVA)
Increased MPO, prolonged t, elevated CVR and increased %H2O
observed in Placebo hearts were all completely averted by Anti-CD18 treatment,
demonstrating complete prevention of myocardial inflammation, diastolic
stunning, low-reflow, and edema.
Conclusion: Leukocyte adhesion is a critical initiating event in reperfusion-induced
myocardial damage after heart transplantation and should be addressed in
treatments directed at limiting reperfusion injury.
*By Invitation
F10. A Long-Term Ventricular Assist System
WILLIAM S. PIERCE, M.D., ALAN J. SNYDER,
Ph.D.*,
GERSON ROSENBERG, Ph.D.*, WILLIAM WEISS,
M.S.*,
WALTER E. PAE, JR., M.D. and
JOHN A. WALDHAUSEN, M.D.
Hershey, Pennsylvania
While cardiac transplantation is excellent therapy
for certain patients with end-stage heart disease, the number of donor hearts
is far less than the need. A permanent left ventricle-to-aortic assist pump has
the potential of providing long-term systemic circulatory support in patients
for whom donor hearts cannot be obtained.
Our multidisciplinary group is developing an
implantable, electrically powered pump that will provide tether-free circulatory
support. The blood pump consists of a seamless polyurethane sac within a
polysulfone case. Bjork-Shiley monostrut valves provide unidirectional flow.
The blood sac is compressed by a pusher plate actuated by a brushless DC
electric motor-motion translator.
The system has gradually
evolved from one in which a tube crossed the skin, serving as a conduit for
electrical wires, to the most recent model in which the unit is completely
sealed and inductive coupling is used to transfer electrical energy across the
intact skin. The current model has an implantable miniature control system as
well as a battery that provides 30 minutes of operation when the external coil
is disconnected. However, during normal operation, the pump is powered by a
portable battery pack or by house current.
The pump has a stroke volume of 62 ml and is
capable of pumping 8.5 l/min, (l0mmHg filling pressure, 120mmHg outlet
pressure). Extensive mock loop testing has demonstrated progressive improvement
in system reliability.
Twenty-six chronic animals have had
circulatory support with an average period of pumping of 62 days, the longest
period of support being eight months. Experiments were terminated in 18 animals
for pump related problems (electromechanical 8, moisture related 6, sac rupture
4) and in 7 for animal related problems (thromboembolic 3, bleeding 2 and
infection 2). One animal is ongoing.
Studies to date are very encouraging and
suggest that, with further refinement, a reliable assist pump can be developed
that will have important clinical application.
*By Invitation
TUESDAY MORNING, April 28, 1992
9:00 a.m. SCIENTIFIC SESSION - Los Angeles Ballroom
13. Aortic Valve Replacement With Pulmonary
Homografts: Early Experience
GINO GEROSA, M.D.*, DONALD N. ROSS, F.R.C.S.
PETER E. BRUECKE, M.D., ANTONI J.
DZIATKOWIAK, M.D.*,
SOPHIA MOHAMMAD, MSc* and
DINO CASAROTTO, M.D.*
Verona, Italy; Linz, Austria; Krakow, Poland;
London, England
The increased use of aortic homografts (AH) as
aortic valve substitute and the limited availability of donor valves prompted
us to consider the pulmonary homograft (PH) as an alternative substitute for
aortic valve replacement (AYR). The aim of our study is to compare the
morphologic, ultrastructural and biomechanical properties of PH leaflets with the
AH leaflets and to present the early phase results using PH for AYR. Light,
scanning and transmission electron microscopy have shown that PH leaflets are
thinner than the aortic with a lesser content of elastic tissue in the
ven-tricularis layer. Moreover there were not marked differences in the
ultrastruc-ture. Uniaxiale tensile tests were carried out on 36 cusps from
human pulmonary and aortic valves using an Instron test machine. The strain at
200 KPa was found to be similar for both pulmonary and aortic leaflets (approx
26%) cut radially. Circumferential strips appear to be more extensible in
pulmonary leaflets, than in aortic (15% and 9% respectively). The ultimate
tensile strength (UTS) for circumferential strips was found to be one and a
half times as large for aortic when compared with pulmonary, but there was
relatively little difference between the radial strips. As far as clinical
experience is concerned, from September 1988 through September 1991, 107
consecutive patients 20-78 years old received either fresh-antibiotic or
cryopreserved PH for AYR. The PH's were inserted in place of patients' diseased
aortic valve with two different techniques: freehand in subcoronary position or
as a "short cylinder" inside the aortic root. There,were 3 hospital deaths
(2.8%). Follow-up was complete (1-36 mo.), all surviving patients have been
followed with serial color flow Doppler echo.cardiography. There were no late
deaths. 3 patients (2.9%) underwent reoperation because of severe aortic
regurgitation (1,4 and 15 mo. post-op.) due to technical problem (mismatch in
size between PH and aortic annulus) in 2 cases and probably due to graft
rejection in 1 case. Mild aortic regurgitation has been detected in 3 patients
(2.9%). No patients incurred in thromboembolicepisodes or infective
endocarditis. According to our results the PH has shown to have ultrastructural
and biomechanical properties similar to that of the AH. Furthermore PH has
shown to be more pliable and easier to insert giving promising short term results.
*By Invitation
14. Infant Repair of Complete Atrioventricular
Canal Defects: 20 Year Trends
FRANK L. HANLEY, M.D.*, RICHARD A. JONAS,
M.D.,
JOHN E. MAYER, JR., M.D. and
ALDO R. CASTANEDA, M.D.
Boston, Massachusetts
Three
hundred nineteen infants with complete atrioventricular canal defects have
undergone surgical repair at our institution from 1972 to 1991. Analysis of
these cases by 5 year intervals reveals a number of important institutional
trends.
|
|
1972-77
|
1977-81
|
1982-86
|
1987-91
|
|
Caseload
|
13
|
63
|
107
|
136
|
|
Assoc. Lesions
|
16%
|
22%
|
22%
|
30%
|
|
1° Repair
|
56%
|
81%
|
87%
|
88%
|
|
Reoperations Within
6 mo
|
31%
|
19%
|
15%
|
8%
|
|
Age 0-6 mo. (Hosp.
Deaths)
|
6(2)
|
26(7)
|
48(8)
|
70(1)
|
|
Age 7-12 mo. (Hosp.
Deaths)
|
7(4)
|
37(11)
|
59(5)
|
66(3)
|
These trends
show increasing volume and complexity of cases over time. In spite of this the
number of cases undergoing primary repair increased and the need for early
reoperation and the in hospital mortality have decreased markedly. The most
recent 5 year experience reveals a 1.5% mortality in patients aged 0 to 6
months at the time of surgery and a 4.5% mortality in patients aged 7 to 12
months (overall 2.9% in hospital mortality).
These data
support primary repair in infancy as the procedure of choice and suggest that
repair before 6 months may provide further benefit. Further analysis suggests
that precise surgical technique, primarily with avoidance of residual mitral
regurgitation and to a lesser extent with avoidance of residual ventricular
level shunting, is an important factor in the improved outcome and can be
reliably achieved in early infancy.
*By Invitation
15. Deep Hypothermia and Circulatory Arrest:
Determinants of Stroke and Early Mortality in 656 Adult Patients
LARS G. SVENSSON, M.D.*, E. STANLEY CRAWFORD,
M.D.,
KENNETH R. HESS, M.S.*, JOSEPH S. COSELLI,
M.D.*
and HAZIM J. SAFI, M.D.*
Houston, Texas
Deep hypothermia with circulatory arrest are being
used more often for complicated cardiovascular surgery, particularly for repair
of the aortic arch and acute aortic dissection. There are, however, few large
studies that have documented the safety of this technique in adults. We have
therefore evaluated our results for this type of adjunct to determine the
independent predictors of early death and postoperative stroke by logistic regression
analysis. Of the 656 patients operated upon between 7/7/79 and 1/30/91, 43% (N
= 283) were female, median age was 64 years (range 10 to 88 years), 12% (N =
77) had acute dissection, 26% (N = 173) had previously had cardiac or ascending
aortic surgery, and 13% (N = 85) had a history of cerebrovascular disease. The
median circulatory arrest time was 31 minutes (range 7 to 120 minutes). The
univariate predictors of transient or permanent stroke, either global or
hemiparetic, which occurred in 44 patients (7%), were (p<0.05): increasing
age, history of cerebrovascular disease, circulatory arrest time (7-29 minutes
= 12/298 [4%]; 30-44 minutes = 15/201 [7.5%]; 45-59 minutes 9/84 [10.7%];
60-120 minutes 7/48 [14.6%]), car-diopulmonary bypass time, and concurrent
descending thoracic aorta repair. The independent determinants for stroke were
(p < 0.05): history of cerebrovascular disease, previous aortic surgery
distal to the left subclavian artery, and cardiopulmonary bypass time. A
history of aortic valve incompetence was associated with a lower risk (adjusted
odds ratio 0.42, p=0.015). The independent determinants for increased risk of
early death, which occurred in 66 (10%) of patients, were (p < 0.05):
increasing age, Mar-fan syndrome, concurrent distal aortic aneurysm, previous
ascending aortic surgery, cardiopulmonary bypass time, cardiac complications,
renal complications, and stroke. We conclude that deep hypothermia with
circulatory arrest is a safe technique for the repair of complex aortic
problems provided circulatory arrest time and cardiopulmonary bypass time is
not excessive. Furthermore, the determinants of stroke and death are
predominantly related to the patients clinical characteristics.
10:00 a.m. INTERMISSION - VISIT EXHIBITS
*By Invitation
10:45 a.m. SCIENTIFIC SESSIONS - Los Angeles Ballroom
16. Intra-Aortic Balloon Pumping in Cardiac
Surgical Patients: Risk Analysis and Long Term Follow-Up
KEITH S. NAUNHEIM, M.D.*, MARC T. SWARTZ,
B.A.*,
D. GLENNPENN1NGTON, M.D.,
GEORGE C. KAISER, M.D., LAWRENCE R. McBRIDE,
M.D.*
and ANDREW C. FIORE, M.D.*
St. Louis, Missouri
The intraaortic balloon pump (IAB) is usually the
first mechanical device inserted for perioperative cardiac failure, however,
little current data is available regarding short and long-term effectiveness.
From Jan. 1983 through Nov. 1990, 6,856 adult patients (pts) underwent cardiac
surgical procedures, 580 of whom (8.5%) had lABs inserted preoperatively
(preop) 107 pts, intraoperatively 419 pts, or postoperatively 54 pts. There were
374 males, 206 females with a mean age of 63.9 yrs (range 19-88). Operations
included 336 CABG, 75 mitral, 54 aortic, 15 double valve replacements and 100
other procedures. Operative mortality for IAB pts was 44%. Univariate and
multivariate analysis of 26 parameters revealed 6 independent predictors of
mortality.
|
Variable
|
Univariate p Value
|
Multivariate p value
|
|
Preop NYHA
|
<0.0001
|
<0.0001
|
|
Transthoracic IAB
|
<0.0004
|
<0.0001
|
|
Preop IV
nitroglycerine
|
<0.007
|
<0.001
|
|
Patient age
|
<0.006
|
<0.001
|
|
Female gender
|
<0.01
|
<0.001
|
|
Preop IAB
|
<0.013
|
<0.001
|
There were 96 (16.5%) lAB-related complications of
which 43 required IAB removal for ischemia and 53 required surgical
intervention. lAB-related surgical procedures included thrombectomy (34),
vascular repair (15), aortic repair (2) and fasciotomy (2). Univariate analysis
demonstrated no relationship between any of the lAB-related complications and
survival. Only 34 of the 580 pts (6%) were lost to follow-up. There were 75
late deaths, the etiology of which was cardiac in 41 (55%), noncardiac in 20
(27%) and unknown in 14 (19%). Actuarial survival at 1, 5 and 9 years is 51%,
42% and 33%. Of the 217 hospital survivors still alive and contacted, 81% were
in NYHA Class I (114) or II (60).
These data show 1) operative mortality for pts
requiring IAB in the perioperative period remains high; 2) perioperative risk
factors can be identified; 3) IAB complications do not effect survival; 4)
operative survivors can achieve prolonged survival with excellent functional
results; and 5) consideration for alternative methods of circulatory support is
justified.
*By Invitation
17. The Effect of Coronary Reoperation on the
Survival of Patients With Stenoses in Saphenous Vein to Coronary Bypass Grafts
BRUCE W. LYTLE, M.D., FLOYD D. LOOP, M.D.,
PAUL C. TAYLOR, M.D.*, ROBERTONOVOA, M.D.*,
MARLENE GOORMASTIC, M.P.H.* and
DELOS M, COSGROVE, M.D.
Cleveland, Ohio
Coronary
reoperations (reop) have not yet been shown to improve survival. To examine the
question of whether coronary reop improves the survival of patients with
stenoses in saphenous vein to coronary bypass grafts (SVG), we retrospectively
reviewed 1117 patients who had coronary bypass surgery then underwent a
postoperative coronary angiogram (stenotic cath) that documented a stenosis
(20-99%) of at least one SVG. Reop within one month of the stenotic cath was
performed for 394 patients (reop group) whereas 723 patients (med group)
received initial medical treatment (no reop or PTCA within 1 year). Compared
with the med group, patients in the reop group were older, more symptomatic,
had a higher incidence of left main stenosis and fewer patent bypass grafts
(all p < 0.001). In-hospital mortality for the reop group was 3.8%. Mean
post cath follow-up of the entire group was 80 months.
Based on the
interval between the primary operation and the stenotic cath, patients were
designated as having early (< 5 yrs.) or late (> 5 yrs.) SVG stenoses.
Univariate and multivariate analyses were used to identify factors influencing
the survival of these subgroups. Reoperation was not identified as a variable
improving the survival of patients with early SVG stenoses.
For patients
with late SVG stenoses, moderate or severe impairment of left ventricular
function, advanced age, triple-vessel or left main stenosis and stenosis in a
SVG to the left anterior descending artery (LAD) (all p < 0.001) decreased
survival while reoperation (p = 0.0015) improved survival. The benefit of reop
was very strong for patients with SVG-LAD stenoses with survival of 84% and 74%
for the reop group versus 76% and 53% for the med group at 2 and 4 post cath
years, respectively (p = 0.004). Even for patients with Class I or II symptoms,
reoperation prolonged survival (p = 0.02 with multivariate testing). This is
the first study showing that coronary reoperation improves the survival of any
patient subset and documents enhanced survival with reoperation for patients
with late SVG stenoses, particularly those with SVG-LAD stenoses.
11:25 p.m. ADDRESS BY HONORED SPEAKER
Coronary Artery Bypass Graft Surgery; Twenty-five Years Later. Some
Landmarks
Rene G. Favaloro, M.D., Buenos Aires, Argentina
12:10 p.m. ADJOURN FOR LUNCH - VISIT EXHIBITS
CARDIOTHORACIC RESIDENTS' LUNCHEON - Century
Room
*By Invitation
