(Circulation. 1995;92:163-168.)
© 1995 American Heart Association, Inc.
Articles |
Early and Late Mortality of Patients Undergoing Aortic Valve Replacement After Previous Coronary Artery Bypass Graft Surgery
From St Luke's Episcopal Hospital and Texas Heart Institute, Houston, Tex.
Correspondence to Sayid F. Fighali, MD, 6624, Fannin, Suite 2780, Houston, TX 77030.
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Abstract |
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Background In a small number of patients who undergo coronary artery bypass graft surgery (CABG), a hemodynamically significant aortic valve lesion requiring aortic valve replacement (AVR) develops as they grow older. In a limited number of studies in small patient groups, high mortality has been shown in patients undergoing AVR after CABG. We undertook this study to determine the mortality risk factors for patients who undergo AVR after CABG procedures.
Methods and Results The outcome of 104 patients treated at our institution between January 1983 and December 1993 was retrospectively reviewed. The initial surgery was CABG in all patients. The patient population included 86 men (83%) and 18 women (17%); their mean age was 67 years. Overall, 70% of patients had congestive heart failure, and 96% had multivessel coronary artery disease. The diagnosis was aortic stenosis in 68% of patients, aortic insufficiency in 16%, and combined aortic stenosis and aortic insufficiency in 16%. Postoperative complications included worsening congestive heart failure (35%), perioperative myocardial infarction (13%), and bleeding (28%). The early mortality was 14%, and the late mortality was 17% (mean follow-up, 35 months). The risk factors for early mortality were number of diseased vessels (P=.028), renal failure (0.000), and prior myocardial infarction (P=.028). A perioperative predictor of early mortality was cardiopulmonary bypass time (P=.000). The risk factors for late mortality included preoperative diabetes mellitus (P=.007), postoperative acute respiratory distress syndrome (P=.011), and ventricular arrhythmias (P=.0001). The survival at 1, 5, and 10 years was 96%, 75%, and 49%, respectively.
Conclusions Risk factors were identified for early and late mortality in patients undergoing AVR after previous CABG. Although early morbidity and mortality were high, the long-term outcome of the survivors was favorable.
Key Words: surgery • bypass • mortality • morbidity • risk factors
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Introduction |
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TopAbstractIntroductionMethods Results Discussion References |
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The surgical results and late outcome of patients undergoing isolated aortic valve replacement (AVR) and AVR with concomitant coronary artery bypass graft surgery (CABG) have been well established.1 2 3 4 5 6 7 8 9 10 Little information is available on AVR after CABG, but studies in small groups of patients have shown a very high perioperative mortality associated with this procedure.11 We observed in a small number of patients with prior CABG that a hemodynamically significant aortic valve lesion requiring AVR develops as they grow older. We thus undertook the present study to examine the early and late outcomes of AVR in patients with previous CABG surgery and to identify predictors of early and late outcome in these patients.
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Methods |
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TopAbstractIntroductionMethods Results Discussion References |
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Patient Data
The study group comprised 104 patients who had undergone AVR after previous CABG between January 1983 and December 1993 at the Texas Heart Institute. Patients undergoing concomitant mitral valve replacement and those with aortic dissection were excluded from the study. Patients were identified through computer-generated records, and in-hospital outcome was determined by review of the patient charts. Long-term follow-up was obtained through questionnaires and telephone calls.
Clinical and Laboratory Data
Etiologic classification of the
aortic valve disease was based
on findings at cardiac catheterization,
echocardiography, surgery, and pathological
examination of the excised valve. On the basis of the clinical
examination with echocardiographic and angiographic
studies, patients were classified as having pure aortic
stenosis (AS), pure aortic insufficiency (AI), or combined AS
and AI.
Cardiac catheterization and coronary angiography were performed routinely before all cardiac operations. Narrowing of the left main coronary artery by more than 50% and narrowing of the other coronary artery branches or bypass grafts by more than 70% were considered significant.
Perioperative myocardial infarction was defined either by the appearance of a new Q wave on the postoperative ECG or when the postoperative MB isoenzyme of creatine kinase was more than 50 units and comprised more than 10% of the total creatine kinase in patients with equivocal ECG changes.
Renal failure was defined as serum creatinine of more than 2.0 mg/dL. Left ventricular ejection fraction was derived from one or more procedures: left ventricular angiography, two-dimensional echocardiography, and left ventricular gated blood pool nuclear study.
Early mortality was defined as any death occurring during or within the first 30 days after surgery. An in-hospital death occurring more than 30 days after surgery was also considered early mortality.
Surgical Procedures
Valvular surgery was classified as
"urgent"
if it had to be performed in patients with clinical or
hemodynamic instability. All patients underwent
cardiopulmonary bypass with systemic hypothermia and
hypothermic blood or crystalloid potassium cardioplegia. Cardioplegic
solution was delivered in an antegrade fashion into either the aortic
root or the coronary ostia directly with hand-held cannulae
when aortic regurgitation was significant. In three
patients, the cardioplegic solution was delivered into the
coronary sinus. Concomitant CABG was performed with the use of
saphenous vein or internal mammary artery bypass grafts. Distal
anastomoses were usually performed before valve replacement to permit
vein graft perfusion with cardioplegic solution. The selection of the
valve prosthesis and the decision to perform CABG were made by
the surgeon.
Statistical Analysis
The survivors were compared with the
nonsurvivors according to
clinical, anatomic, and surgical variables (Table 1
).
2 and Student's t
tests were used for univariate analysis; those with
P
.5 were incorporated into a model of
multivariate analysis with the use of
SAS-STAT software. Logistic regression was used for early
death with the logistic procedure. Cox regression was used for late
death with the PHREG procedure. P<.05 was
considered significant. A survival curve was constructed with the life
test procedure.
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Results |
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TopAbstractIntroductionMethods Results Discussion References |
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Initial Surgery
The initial surgery was CABG in all patients (Table 2
). The mean number of bypasses grafted was 2.9 per
patient. The mean time interval between the initial surgery and the
index AVR surgery was 9.0±3 years. The mammary artery was rarely used
as a bypass graft in the initial surgery.
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Clinical and Laboratory Data at Index AVR Surgery
Overall,
the patient population was older (mean age, 67 years),
and the majority were men (Table 3). The most common
symptoms at presentation in order of frequency were
congestive heart failure, angina, and hypertension. Prior myocardial
infarction was noted in 38 patients. Three patients (3%) had evidence
of bacterial endocarditis.
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AS was documented in 68% of patients, AI in
16%, and combined AS and
AI in 16%. The incidence of one-, two-, and three-vessel
coronary artery disease (CAD) was 4%, 15%, and 81%. Left
ventricular ejection fraction was severely reduced (30%)
in 18 patients (22%).
Index AVR Surgery
Surgery was performed on an urgent basis in
3 patients (3%)
and as an elective procedure in 101 patients (97%) (Table 4).
The operation was AVR in 45 patients (43%) and AVR
with concomitant CABG in 59 patients (57%), with a mean of 1.9
bypasses grafted per patient. A mechanical prosthesis was used
in the majority of patients (92%). Based on pathological examination,
the aortic lesion was determined to be calcific degeneration in 64%,
bicuspid aortic valve in 12%, and rheumatic disease in 8% of
patients, respectively. Six additional patients (6%) had ectasia of
the ascending aorta.
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Complications
Major postoperative complications occurred in
63 patients (61%)
(Table 5). The most common postoperative complications
were congestive heart failure, severe bleeding requiring surgical
exploration and/or transfusion with more than 4 units of blood,
supraventricular and ventricular
arrhythmias, low cardiac output, sepsis,
perioperative myocardial infarction (MI), acute
respiratory distress syndrome, renal failure, and cerebrovascular
accident. The diagnosis of perioperative MI was based
on ECG criteria in 13 patients and on elevation of the MB isoenzyme of
creatine kinase in one additional patient, with evidence of poor R-wave
progression in the anterior chest leads. Perioperative
MI occurred in two patients undergoing AVR alone and in 12 patients
undergoing AVR and concomitant CABG (P=.019).
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Early Mortality
Early mortality (30 days after surgery)
was documented in 15
patients (14%), with 3 intraoperative and 12 postoperative deaths. The
most common causes of death were congestive heart failure and low
cardiac output in 12 patients (80%), ventricular
arrhythmias in 3 patients (20%), severe bleeding in 2 patients
(13%), cerebrovascular accident in 1 patient (7%), and acute
respiratory distress syndrome in 1 patient (7%). Some patients who
died early had more than one of these diagnoses.
Predictors of Early Mortality
Univariate Analysis
Univariate analyses were performed based on 36
preoperative and intraoperative variables that were
analyzed for possible relation to surgical mortality (Table 1
).
By univariate analysis, the preoperative predictors
of early mortality were unstable angina, prior MI, multivessel CAD,
renal failure, and cerebrovascular accident (Table 6).
The perioperative univariate predictors
were surgery performed on an emergency basis, the need for
intra-aortic balloon pump assistance at the end of surgery, and
longer cardiopulmonary bypass time.
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Multivariate Analysis
Preoperative predictors of early postoperative mortality by
multivariate analysis were renal failure, prior
MI, and multivessel CAD. A perioperative predictor was
longer cardiopulmonary bypass time (Table 7).
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Late Outcome
Follow-up was obtained in 89% of patients. The
mean
follow-up was 35 months. The late mortality was 17%. The survival
rate at 1, 5, and 10 years was 96%, 75%, and 49%, respectively.
Early perioperative death was not taken into
consideration (Figure).
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Multivariate Predictors of
Late
Mortality
The preoperative predictor of late mortality was diabetes
mellitus
(Table 8). Postoperative predictors included
ventricular arrhythmias and acute respiratory
distress syndrome.
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Discussion |
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TopAbstractIntroductionMethods Results Discussion References |
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Most of the disease processes that commonly involve the aortic valve have been shown to progress in severity with advanced age.12 13 14 These include degenerative calcific aortic valve, rheumatic aortic valve disease, and congenital bicuspid aortic valve. As the cohorts of patients who had CABG over the past 25 years grow older, the incidence of a hemodynamically significant aortic lesion requiring AVR is expected to rise accordingly. Some studies have suggested that concomitant CAD can accelerate the rate of progression of AS.14 The present study was initiated to examine the early and late outcomes of AVR in patients with prior CABG.
Previous Studies
Early Mortality
The surgical
mortality associated with AVR has been
progressively decreasing because of improvements in myocardial
preservation, surgical techniques, and postoperative care. In most
institutions, the risk of early mortality in isolated AVR has been
reported to range from 2% to
6%.1 4 5 6 7 8 9 10
The predictors of
early mortality include age, left ventricular function,
prior aortic valve surgery, aortic insufficiency, and the presence of
CAD.1 2 3 4 5 6 7 8 13
Although concomitant CABG may improve the
long-term results for patients with aortic valve disease and CAD,
it also increases the risk of early
mortality.1 5 6 9
AVR and CABG Procedures
Kirklin and
colleagues1 2 reported an early mortality
of 2.9% in patients with primary isolated AVR, 6.5% with repeat AVR,
and 9% with concomitant AVR and CABG. Mullany et al4
compared early mortality in patients with CAD and aortic disease
undergoing AVR only with similar patients undergoing AVR and CABG:
mortality was 6.3% for AVR alone and 10% for AVR and CABG. Although
the difference between these rates was not statistically significant, a
definite trend toward higher mortality in the AVR/CABG group was
noted.
A group from the University of Toronto7 published their experience with AVR in elderly patients; mortality was 7.6% in patients older than 70 years versus 5.8% in patients younger than 70. The mortality was 11.5% in patients with concomitant CAD treated with CABG and 21% in patients with CAD with no surgical intervention. In the Veterans Administration Cooperative Study, the mortality for AVR was 8.3% and increased to 12.8% in patients with three-vessel CAD.5 The mortality in patients with previous cardiac operations was 30.4%. Collins and Aranki11 reported 44 patients who underwent AVR after previous CABG. The mean interval between both procedures was 68 months, and 24 patients had evidence of mild-to-moderate AS at the time of CABG. The surgical mortality of AVR in this group was 18.2%. Based on this high mortality rate, the authors concluded that concomitant AVR should be performed in patients with evidence of mild-to-moderate AS at the time of CABG.
In the present study, the 104 patients had no evidence of significant aortic valve disease at the time of the initial CABG procedure and the mean interval between both operations (109 months) was longer than that reported in the study of Collins and Aranki.11 This lessens the likelihood that AVR would have been necessary at the time of initial CABG procedures in our patients.
Effect of CAD on Surgical Outcome
It has
been demonstrated that CAD decreases the tolerance of the
hypertrophied myocardium to ischemia, thereby
interfering with myocardial preservation during open heart
surgery.1 15 16 In the present study, we
had the
opportunity to study the effect of patent vein grafts from a prior
surgery on myocardial preservation and perioperative MI
during AVR. Patent vein grafts from a prior CABG may improve myocardial
preservation during AVR by allowing cardioplegic solution to reach
distal coronary arterial beds beyond areas of
proximal stenosis. Mammary artery grafts, however, do not
provide the same protection. In the present study, 14 patients
(13%) had evidence of a new transmural MI after AVR.
Perioperative MI occurred more frequently when CABG was
performed concomitant with AVR. The presence of CAD at the time of AVR
procedures has been reported to be associated with a higher incidence
of perioperative MI.17 18 19 Iung and
colleagues17 reported a perioperative rate
of MI of 0.7% after AVR in patients with normal coronary
arteries and 6.9% in patients with aortic valve disease and CAD
undergoing AVR and CABG. Reed and colleagues19 reported a
7.6% incidence of perioperative MI after AVR and CABG.
MI was diagnosed by ECG criteria and/or elevation of the MB isoenzyme
of creatine kinase. With ECG criteria, Jones et al18
reported a perioperative MI rate of 17% after AVR and
15% after AVR plus CABG in a group with aortic valve disease and
concomitant CAD. Our findings indicate that patent vein grafts from
previous CABG do not lower the incidence of
perioperative MI at the time of AVR. This study also
reveals that patients who do not have concomitant
revascularization while undergoing AVR after
previous CABG have a lower perioperative MI rate.
Some investigators believe that in the presence of severe CAD, retrograde delivery of cardioplegic solution through the coronary sinus generates better global distribution of cardioplegia and cooling than does antegrade delivery and can help optimize preservation of myocardium in jeopardy during surgery.20 This technique was uncommonly used at our institution at the time of this study.
Predictors of Early Mortality
All five predictors of early
mortality by univariate
and multivariate analyses in this study are
related to variables and conditions already known to affect results
of AVR and heart surgery in general. These factors are reported to
include age, left ventricular function, associated systemic
illnesses, prolonged ischemic time, prior heart surgery, and
low cardiac output at the end of the surgical
procedure.1 2 3 4 5 6 7 8 9 10 11
Several variables that correlated with
early mortality by multivariate analysis,
however, were not found to be independent predictors of early mortality
by multivariate analysis. These variables
were preoperative cerebrovascular accident, preoperative unstable
angina, emergency surgery, and the use of IABP after surgery.
Reduced left ventricular contractility has been shown repeatedly to be associated with a poor early and late outcome after AVR, for both AS and AI.1 3 7 8 9 10 The combination of CAD and aortic valve disease can alter ventricular function by different mechanisms, including increased wall stress, myocardial ischemia, and MI.15 16 It is interesting that a prior MI—and not left ventricular ejection fraction—in this study was an independent predictor of poor outcome because areas of MI are not expected to regain function after the aortic lesion is corrected. The finding of increased mortality in the subgroup of patients with multivessel CAD is concordant to reports in which patients with combined aortic valve disease and CAD with a higher number of diseased coronary artery vessels have a higher surgical mortality.5 7 8 An independent perioperative predictor of early mortality was prolonged cardiopulmonary bypass time.
Perioperative MI, however, was not found to be an independent predictor of early mortality.
Other factors that did not significantly affect early mortality included age, nature of the aortic lesion (AS, AI, or combined AS and AI), and concomitant coronary artery bypass revascularization at the time of the index surgery.
Late Results
The incidence of late mortality in our series
was higher than that
reported after isolated AVR but similar to that of patients with AVR
and concomitant CABG. Kirklin and Barratt-Boyes1 had
reported an overall survival of 91% and 77% at 1 and 5 years after
isolated AVR. In the series reported by Magovern and
colleagues,6 in which 52% of patients had AVR plus CABG,
72% of hospital survivors were alive at 48 months. In a report from
the Cleveland Clinic9 of patients with AVR and CABG, the
survival rate was 89%, 79%, and 52% at 2, 5, and 10 years,
respectively. Previously reported risk factors for late mortality after
AVR include old age, poor New York Heart Association functional class,
ventricular enlargement or dysfunction,
coexistent CAD, mitral regurgitation, and
ventricular
arrhythmias.1 2 3 4 5 6 7 8 9 10
In our
study, the preoperative predictor of late mortality was diabetes
mellitus. The postoperative predictors of late mortality were acute
respiratory distress syndrome and postoperative ventricular
arrhythmias. Age and left ventricular ejection
fraction were not factors for late mortality in this study.
Conclusions
In the present study, we identified predictors of
early and
late mortality in patients undergoing AVR after previous CABG. Early
and late outcomes were not affected by the nature and etiology of the
aortic valve lesions (AS, AI, or combined AS and AI; degenerative
versus other pathological lesions). Although AVR after a previous CABG
procedure is associated with a high rate of early morbidity and
mortality, the long-term outcome of survivors appears
favorable.
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