Circulation. 1995;92:50-57
(Circulation. 1995;92:50-57.)
© 1995 American Heart Association, Inc.
In-Hospital and Long-term Outcome After Reoperative Coronary Artery Bypass Graft Surgery
William S. Weintraub, MD;
Ellis L. Jones, MD;
Joseph M. Craver, MD;
Ralph Grosswald, BS;
Robert A. Guyton, MD
From the Divisions of Cardiology and Cardiothoracic Surgery, Emory
University School of Medicine, Atlanta, Ga.
Correspondence to William S. Weintraub, MD, Division of Cardiology, Emory
University Hospital, 1365 Clifton Rd NE, Atlanta, GA 30322.
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Abstract
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Background Increasingly over the past several years,
patients
have returned after coronary surgery for reoperative
procedures,
and the experience has become substantial. In this report,
we
describe immediate- and long-term outcomes after reoperative
coronary
artery bypass graft surgery.
Methods and Results The source of data was the clinical
database at Emory University. The surgical procedure and statistical
methods were standard. Data were collected prospectively and entered
into a computerized database. Follow-up was by letter, telephone,
or hospital records documenting additional events resulting in
readmission. In-hospital correlates of survival were determined by
logistic regression, and long-term correlates were determined by
Cox model analysis. There were 2030 patients with a mean age of
61 and a mean of 7.8±4.1 years since the first surgery. The mean
ejection fraction was close to 50%, and the majority had
three-vessel or left main disease. Urgent or emergency surgery was
required in 16.6%. The internal mammary was used in 60.1%. Q-wave
myocardial infarctions occurred in just over 5%. Neurological events
increased from 1.2% at less than age 50 to 4.1% at more than age 70.
The hospital mortality increased from 5.7% at less than age 50 to 10%
at more than age 70, with an overall rate of 7.0%. Mortality was 5.7%
for elective, 10.9% for urgent, and 16.4% for emergency cases.
Angina was noted at follow-up in 41.3%. Urgent or emergency
surgery, reduced ejection fraction, hypertension, older age, and female
sex were univariate and multivariate
correlates of in-hospital death. Diabetes was a
univariate correlate only. Five- and 10-year survival rates
were 76% and 55%, respectively. Five- and 10-year myocardial
infarction–free survival rates were 63% and 40%, respectively.
By 12 years, few patients were free of cardiac events. The
univariate and multivariate correlates of
long-term mortality were older age, reduced ejection fraction,
hypertension, diseased vessels, presence of diabetes, congestive
failure, and emergency surgery, with a strong trend for female sex. The
use of the internal mammary artery was not a correlate for
long-term mortality.
Conclusions Patients undergoing reoperative procedures have
higher mortality initially and at long term than patients undergoing a
first procedure. Expected mortality based on covariates may help in the
decision of whether to perform reoperative coronary artery
bypass graft surgery.
Key Words: surgery • aging • bypass • mortality • morbidity
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Introduction
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Coronary artery bypass
graft surgery (CABG) may be limited by
incomplete
revascularization, graft failure, and progression
of
narrowing in the native coronary arteries. Each of these
problems
alone or, more likely, in combination may lead to the need for
reoperative
CABG, which was first described within a few years of the
first
coronary surgical procedures.
1 The problems
of progression
and graft failure accelerate after approximately 8
years, leading
to an increased incidence of reoperative
procedures.
2 Furthermore,
reoperative CABG has been shown
to be an increasing part of
current surgical
practice.
3 4
In the present study, we examine
the in-hospital and
long-term outcomes of reoperative CABG.
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Methods
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Patient Population
The study population comprised patients
undergoing a first
reoperation
at Emory University Hospitals between 1975 and 1993.
Patients
with valve disease, congenital heart disease, or primary
myocardial
diseases and patients requiring aneurysmectomy were
excluded.
The total population was 2030 (mean age, 61±9 years),
and
2011 (99%) had follow-up (mean, 4.3±3.2 years).
Surgical Technique
Extracorporeal circulation was instituted
by standard
techniques,5 and perfusion was maintained at 2.0 to 2.4
L · min-1 · m-2. Systemic
hypothermia
(30°C to 25°C), topical hypothermia, and cold potassium
cardioplegia were used for myocardial protection. Cardioplegic solution
was reinfused at 20- to 30-minute intervals to maintain an
intramyocardial temperature of <20°C. After the patient was weaned
from cardiopulmonary bypass, the chest was closed with
standard techniques. The patients were then transferred to the surgical
intensive care unit.
Definitions
Angina was defined by the Canadian
Cardiovascular Society classification.6
The historical variables of previous myocardial infarction,
diabetes mellitus, systemic hypertension, and prior myocardial
infarction were obtained for the patient. An artery was considered
stenotic if there was 
50% diameter narrowing of a main
coronary artery or any of its major branches. The number of
arteries narrowed was determined by a set algorithm.7
Urgent surgical status was defined as surgery necessary within 1 day
and emergency surgical status as surgery necessary within 1 hour
because of symptoms or hemodynamic instability. The
number of grafts was determined by the number of distal anastomoses. A
postoperative myocardial infarction was determined by the development
of new Q waves. A neurological event was a persistent change in
neurological function, including disorientation persisting for several
days.
Data Analysis
All data were prospectively collected and
entered into a
computerized database. Data are displayed as a percentage or mean±SD
where appropriate. Categorical variables were compared by
2, and continuous variables were
analyzed by ANOVA. Where data are displayed by decade,
P values refer to the total trend in the population by
decade. Long-term survival was determined for the entire population
(in-hospital deaths and survivors) by the Kaplan-Meier
method,8 and correlates of survival were determined by the
Cox proportional hazards method.9 Statistical testing was
performed with BMDP.
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Results
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Clinical characteristics, by decade of age, are given in Table
1
.
The percentage of women rose from 13.9% under age 50
to 20.7%
over age 70. The majority had had a previous myocardial
infarction.
Hypertension was present in approximately half the
patients,
whereas three of four had class III or IV angina. Congestive
heart
failure and diabetes were present in a minority of patients.
The
time from the first CABG increased from 5.7 years under age
50 to
9.3 years over age 70. Angiographic characteristics are
shown in Table
2
. The mean ejection fraction was close to 50%,
and a
sizable minority had ejection fractions of less 50%. The
majority had
three-vessel or left main disease, with a small
increase in the
severity of disease in older patients. Procedural
characteristics and
outcome are displayed in Table 3
. Urgent
or emergency
surgery was required in a minority. The number
of grafts placed
increased with age. The internal mammary was
used in the majority.
Q-wave myocardial infarctions occurred
in just over 5%. Neurological
events increased from 1.2% under
age 50 to 4.1% over age 70. The
hospital mortality increased
from 5.7% under age 50 to 10% over age
70. Angina was common
at follow-up but decreased from 50.8% under
age 50 to 25.7%
over age 70. There were 95 patients in this series
from before
1980, 376 from 1980 through 1984, 778 from 1985 through
1989,
and 781 since 1990. Over these time periods, age increased from
53±8
to 64±9 years, ejection fraction fell from 57±13%
to
48±13%,
the incidence of three-vessel or left main
disease rose from 45.7%
to 77.1%, and the incidence of hypertension
increased from 35.9% to
51.8% (all
P<.001). There was no
consistent
pattern to frequency of emergency surgery and no
change noted in sex.
Despite relatively profound changes in
patient population, there were
no differences noted in in-hospital
outcomes of Q-wave myocardial
infarction, neurological events,
or death over this period.
The clinical, angiographic, and procedural characteristics in Tables 1
through 3
were used to determine
the in-hospital mortality. The
univariate and multivariate odds ratios as
well as P values for in-hospital mortality are displayed in
Table 4. For ejection fraction and age, the odds ratios
refer to an increase of 1 unit, for example, age 62 to 63 years or
ejection fraction from 46% to 47%. Urgent and emergency surgery,
reduced ejection fraction, hypertension, older age, and female sex were
univariate and multivariate correlates. The
univariate and multivariate odds ratios
were similar. Diabetes was a univariate correlate only. For
elective surgery, the mortality was 5.7%; for urgent surgery, 10.9%;
and for emergency surgery, 16.4%.
Long-term survival; myocardial infarction–free survival;
freedom from death, myocardial infarction, and a third coronary
surgery; and survival free of myocardial infarction, a third
coronary surgery, and angioplasty are shown as a layered set of
survival curves in Fig 1. There is an initial dip in the
curves representing in-hospital events; thereafter, the
curves become quite linear. Although survival may seem somewhat
reassuring at 76% at 5 years, it fell to 55% at 10 years. Myocardial
infarc-tion was the other major event. The additional influence of
further revascularization procedures seemed
somewhat less. Nevertheless, by 12 years, few patients were free of
cardiac events. Fig 2 shows the freedom from additional
revascularization procedures, which appear more
prominent on this figure than on Fig 1 because patients may
have had
other events, thereby masking the incidence of additional procedures.
Freedom from a third coronary
revascularization procedure, coronary
angioplasty, and additional revascularization of
either type are shown. Note that additional procedures are at first
unusual, but that after 6 to 8 years, repeat
revascularization becomes more common.
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Figure 1. Twelve-year event-free survival after
reoperative coronary surgery. CABG indicates coronary
artery bypass graft surgery; FF, freedom from; PTCA,
percutaneous transluminal coronary angioplasty;
and MI, myocardial infarction.
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Figure 2. Twelve-year event freedom from a third
coronary bypass surgery, coronary angioplasty, or
either form of revascularization. CABG
indicates coronary artery bypass graft surgery; PTCA,
percutaneous transluminal coronary
angioplasty.
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The clinical, angiographic, and procedural characteristics in Tables 1
through 3 were used to determine
long-term correlates of mortality.
The univariate and multivariate hazard
ratios as well as P values for long-term mortality are
given in Table 5. For ejection fraction and age, the
hazard ratios are for an increase of 1 unit. The univariate
and multivariate correlates were older age, reduced
ejection fraction, hypertension, diseased vessels, presence of
diabetes, congestive heart failure, and urgent or emergency surgery
with a strong trend for female sex. The use of the internal mammary
artery was not a correlate of long-term mortality. The hazard ratio
of 1.04 per year of age may also be expressed as 1.49 for each decade
increase in age (95% confidence interval, 1.32 to 1.69). Similarly,
patient characteristics were used to determine correlates of additional
procedures. The only multivariate correlates of
additional procedures were male sex (P=.0072) and younger
age (P=.0076). Men had a hazard ratio of 1.67 (95%
confidence interval, 1.12 to 2.49) for additional procedures, and the
hazard ratio was 1.21 (95% confidence interval, 1.05 to 1.39) for each
decade decrease in age.
Survival divided by age groups is shown in Fig 3. There
was little difference between patients under age 50 and between ages 50
and 59. Thereafter, mortality rose significantly. Although few patients
over age 70 were alive after 10 years, survival longer than this for
patients over age 70 undergoing reoperative surgery should not be
expected. Note that patients over age 70 were 9.3 years from their
original surgery and thus by 12 years would be over age 80 and more
than 20 years from their original surgery. Survival, divided by
ejection fraction 50%, 35% to 49%, and <35%, is shown in Fig
4. Note that the difference between the curves is
largely established in the first 1 to 2 years, and thereafter the
curves continue to separate more slowly. Survival divided by the
presence or absence of hypertension is shown in Fig 5.
Here, the curves are initially close together but splay out and become
more separated over time. Survival divided by vessels diseased is
displayed in Fig 6. Although the curves do not separate
as cleanly as in several of the other figures, a progression of
increased mortality from single to left main disease may be noted.
Survival divided by the absence and presence of diabetes is
presented in Fig 7. Similar to the curves for
hypertension, the curves for diabetes splay out over time, so that
survival by 10 to 12 years for patients with diabetes is very poor.
Survival divided by the presence or absence of congestive heart failure
is shown in Fig 8. These curves separate rapidly but
then fall in parallel, similar to those for ejection fraction but with
less separation. Survival divided by elective, urgent, or emergency
surgery is shown in Fig 9. The separation is essentially
immediate, reflecting initial in-hospital mortality.
Thereafter, the curves begin to come together, so that by 7 or 8 years
the curves overlap. Survival by sex is displayed in Fig 10.
Women have somewhat lower survival rates, although
the curves are close.
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Discussion
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In the present study, the immediate- and long-term
outcomes
after reoperative coronary surgery have been
presented in a
large patient population. The in-hospital
mortality was 7%,
and 1-, 5-, and 10-year mortality was 11%, 23%,
and 45%. The
major correlate of in-hospital mortality was
emergency surgery,
and of long-term mortality, older age. The other
major complications
in-hospital were acute Q-wave myocardial
infarction in 5.6%
and neurological events in 2.8%. The constancy of
in-hospital
results despite an older and more severely diseased
population
in recent years suggests gradually improving techniques. The
high
in-hospital mortality with emergency surgery suggests that
control
or prevention of perioperative ischemia
may be useful in lowering
in-hospital mortality. There was a
continuing incidence of myocardial
infarction after hospital discharge
as well as additional revascularization
procedures.
The in-hospital mortality rate was higher and long-term
survival rate was lower than in multiple series of first
revascularization procedures. In a recent
publication examining long-term outcome from Emory University, the
in-hospital mortality was 1.0%, and 5- and 10-year survival rates
were 91% and 78%, respectively. Five- and 10-year myocardial
infarction–free survival rates were 83% and 65%, respectively.
The patients in that series were younger and had less severe angina,
fewer previous myocardial infarctions, less hypertension, less
congestive heart failure, less diabetes, less severe coronary
disease, and higher ejection fractions than those in the
present study. In the randomized portion of CASS, the 5- and
10-year survival rates were 95% and 82% in the surgical
arm,10 respectively. The patients in CASS were younger and
had less angina and less severe disease. Van Brussel et
al11 noted 5- and 10-year survival rates of 94% and 82%,
respectively. These patients were also younger and had less severe
disease, less diabetes, less hypertension, and less heart failure than
those in the present study. Rahimtoola et al12
reported 5- and 10-year survival rates of 88% and 73%, respectively.
These patients were also younger and had less diabetes, less
hypertension, and fewer previous myocardial infarctions than the
patients in this study. Loop et al13 also noted lower
long-term mortality rates for first-time surgery and for
patients who were younger and more often male and had less severe
angina and less severe anatomic disease. Lowrie et al14
noted 5-year survival rates of 80% to 85% and 10-year survival rates
of 65% to 70%. The patients were younger and had less severe disease,
better left ventricular function, and less diabetes than in
this series. Similar results were also noted in the European
Cooperative study15 and the VA Cooperative
study16 and in results from the Duke University
database.17
Compared with a wealth of data concerning first-time
coronary surgery, the data on reoperative surgery are more
scant. Kirklin and Barratt-Boyes18 noted that
in-hospital mortality after coronary surgery is
approximately twice that of first surgery. In the CASS registry
experience, 9086 patients having a first procedure were compared with
283 patients having a reoperative procedure.19 The
mortality and myocardial infarction rates after a first procedure were
3.1% and 6.4% versus 5.3% and 5.8%, respectively, for a reoperative
procedure. The patients undergoing reoperation were younger (mean age,
52±9 years in the CASS experience) and had less severe anatomic
disease than in the present report. In the largest series, Loop et
al20 reported on results in 2509 patients. Mortality
ranged from 2% to 5%, and new Q-wave myocardial infarctions ranged
from 4% to 8%, with improved results toward the end of the series.
For hospital survivors, the 10-year survival rate was 69.3%, and
event-free survival was 41.2%. Thus, these patients probably have
not had as good a prognosis as first-time surgical patients. In
addition, these patients were younger and had less diabetes and less
hypertension than those in the present series. In contrast to the
present study, Loop et al13 noted improved survival in
patients with internal mammary artery grafts, although this was not as
important as in their study of first surgeries.
There is an alternative to coronary surgery for at least some
patients in the form of interventional procedures in the
catheterization laboratory. In a recent series from
Emory University of vein graft angioplasty, the in-hospital
mortality was 1.2%, Q-wave myocardial infarction rate was 2.2%, and
rate of need for emergency coronary surgery was
3.5%.21 Restenosis in vein grafts is probably
a more severe problem than in native vessels, and new devices such as
atherectomy and stents may lower the rate of restenosis.
There are little comparative data on the devices, and the little that
there are show little difference in outcome.22 There are
little data comparing interventional procedures with reoperative
surgery. In a recent preliminary, observational comparison, the
long-term results of interventional procedures were superior to
those of reoperative surgery, but the selection bias could not be
accounted for.23 There are no randomized data and no trial
in planning as far as we know. It is not at all certain that the
patients treated with interventional procedures are similar in clinical
or angiographic characteristics to patients undergoing reoperative
surgery. Although the patients undergoing surgery would be expected to
be older and to have more severe disease, this may not always be the
case, as some patients with very severe disease may be referred to
angioplasty as a last-ditch rescue.
How, then, are patients to be cared for after coronary
surgery? There certainly are data on increasing incidence of
reoperative procedures after a period of years, suggesting that
progression of native vessel disease, graft failure, or both accelerate
after approximately 8 years.2 24 25 In
patients with
recurrent symptoms unresponsive to medical therapy, referral for
revascularization is reasonable. Deciding how to
follow and when to catheterize and then revascularize
asymptomatic patients with positive noninvasive testing
and angiographic evidence of ischemic potential is much more
difficult. The decision must be tempered with the knowledge that these
patients have severe disease and will continue to have problems after
palliative surgery. Multivariate models such as those
developed in the present study may be used to more accurately
determine both immediate- and long-term prognosis. Nevertheless,
there is no adequate substitute for good comparative studies that will
permit the assessment of which patients are needing additional
revascularization and of the overlapping patients
who are suitable for either catheter-based or surgical procedures.
Finally, studies are needed comparing the costs in relation to the
clinical outcomes of the various forms of
revascularization after coronary
surgery.
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Top
Abstract
Introduction
