|
|
Predictors of Cardiac Events After Major Vascular
Surgery
Role of Clinical
Characteristics, Dobutamine Echocardiography, and  -Blocker Therapy
 Eric Boersma, PhD; Don Poldermans, MD, PhD; Jeroen J. Bax, MD, PhD;
Ewout W. Steyerberg, MD, PhD; Ian R. Thomson, MD; Jan D. Banga, MD, PhD;
Louis L. M. van de Ven, MD, PhD; Hero van Urk, MD, PhD; Jos R. T. C.
Roelandt, MD, PhD; for the DECREASE Study Group
Context Patients who undergo major vascular surgery are at increased
risk of perioperative cardiac complications. High-risk patients can be
identified by clinical factors and noninvasive cardiac testing, such as
dobutamine stress echocardiography (DSE); however, such noninvasive imaging
techniques carry significant disadvantages. A recent study found that
perioperative  -blocker therapy
reduces complication rates in high-risk individuals.
Objective To examine the relationship of clinical characteristics, DSE
results, -blocker therapy,
and cardiac events in patients undergoing major vascular surgery.
Design and
Setting Cohort study conducted
in 1996-1999 in the following 8 centers: Erasmus Medical Centre and Sint
Clara Ziekenhuis, Rotterdam, Twee Steden Ziekenhuis, Tilburg, Academisch
Ziekenhuis Utrecht, Utrecht, and Medisch Centrum Alkmaar, Alkmaar, the
Netherlands; Ziekenhuis Middelheim, Antwerp, Belgium; and San Gerardo
Hospital, Monza, Istituto di Ricovero e Cura a Carattere Scientifico, San
Giovanni Rotondo, Italy.
Patients A total of 1351 consecutive patients scheduled for major
vascular surgery; DSE was performed in 1097 patients (81%), and 360 (27%)
received -blocker therapy.
Main Outcome
Measure Cardiac death or
nonfatal myocardial infarction within 30 days after surgery, compared by
clinical characteristics, DSE results, and -blocker use.
Results Forty-five patients (3.3%) had perioperative cardiac death or
nonfatal myocardial infarction. In multivariable analysis, important clinical
determinants of adverse outcome were age 70 years or older; current or prior
angina pectoris; and prior myocardial infarction, heart failure, or
cerebrovascular accident. Eighty-three percent of patients had less than 3
clinical risk factors. Among this subgroup, patients receiving -blockers had a lower risk of cardiac complications (0.8%
[2/263]) than those not receiving -blockers (2.3% [20/855]), and DSE had minimal additional
prognostic value. In patients with 3 or more risk factors (17%), DSE provided
additional prognostic information, for patients without stress-induced
ischemia had much lower risk of events than those with stress-induced
ischemia (among those receiving -blockers, 2.0% [1/50] vs 10.6% [5/47]). Moreover, patients with
limited stress-induced ischemia (1-4 segments) experienced fewer cardiac
events (2.8% [1/36]) than those with more extensive ischemia ( 5 segments, 36% [4/11]).
Conclusion The additional predictive value of DSE is limited in clinically
low-risk patients receiving -blockers. In
clinical practice, DSE may be avoided in a large number of patients who can
proceed safely for surgery without delay. In clinically intermediate- and
high-risk patients receiving -blockers, DSE
may help identify those in whom surgery can still be performed and those in
whom cardiac revascularization should be considered.
JAMA. 2001;285:1865-1873
Patients with severe peripheral vascular
disease frequently have underlying coronary artery disease. Hence, patients
undergoing major vascular surgery are at increased risk for cardiac
complications during or shortly after surgery. Appropriate patient management
then includes assessment of the perioperative cardiac risk, as well as
strategies to reduce this risk. Several investigations demonstrated the utility
of dobutamine stress echocardiography (DSE) for preoperative cardiac risk
assessment.1-5 Patients
with stress-induced new wall-motion abnormalities (NWMAs), a hallmark of
myocardial ischemia, are at an 8% to 38% risk of cardiac death or myocardial
infarction (MI) within 30 days after surgery.2, 4, 6, 7 In contrast,
patients without NWMAs have much lower complication rates: in the range of 0%
to 5%. There are, however, significant disadvantages associated with the
routine use of DSE (or other noninvasive imaging techniques) in all vascular
surgery candidates. These include the substantial costs of the test, and,
more importantly, the risk of delaying surgery in patients with large aortic
aneurysms or critical limb ischemia. The recent Dutch Echocardiographic
Cardiac Risk Evaluation Applying Stress Echocardiography (DECREASE) study
demonstrated that perioperative -adrenergic blockade with bisoprolol reduces the risk of 30-day
complications in patients with NWMAs to a risk level as observed in patients
without NWMAs.8, 9 This finding raises
the question of whether DSE is indicated in all patients scheduled for
vascular surgery. Does simple perioperative administration of -blockers reduce or eliminate the need for noninvasive
preoperative cardiac testing?10 On the other hand,
in some patients the cardioprotective effect of -blockers may be insufficient to effectively reduce
perioperative cardiac events. These patients may benefit from additional
coronary revascularization. To address these issues we studied the
relationship between clinical characteristics, DSE results, -blockers, and adverse cardiac outcome in a large series
of consecutive patients scheduled to undergo major vascular surgery.
METHODS
Patients
The study population consisted of 1351 consecutive patients scheduled for
elective major vascular surgery who were screened for eligibility for the
DECREASE study at 8 of the following participating centers: Erasmus Medical
Centre and Sint Clara Ziekenhuis, Rotterdam, Twee Steden Ziekenhuis, Tilburg,
Academisch Ziekenhuis Utrecht, Utrecht, and Medisch Centrum Alkmaar, Alkmaar,
the Netherlands; Ziekenhuis Middelheim, Antwerp, Belgium; and San Gerardo
Hospital, Monza, Istituto di Ricovero e Cura a Carattere Scientifico, San
Giovanni Rotondo, Italy.8 Per protocol, 846
patients with at least 1 of the following risk factors underwent DSE: age 70
years or older, angina, prior MI, congestive heart failure, treatment for
ventricular arrhythmias, treatment for diabetes mellitus, or limited exercise
capacity. Two hundred forty-five additional patients underwent DSE at the
discretion of the treating physician, based on other risk factors (eg,
hyperlipidemia and smoking). Thus, in total 1091 patients (81%) underwent
DSE. Perioperative -blockers were
administered to 360 patients (27%): 301 (22%) of the 1351 patients were
treated long-term with -blockers, and 59
(5%) were randomized to receive -blockers within the framework of the DECREASE study. Eight
patients who had extensive resting and/or stress-induced ischemia were
excluded from the DECREASE study. Four of these underwent coronary artery
bypass graft surgery, and 2 of them died during this operation. The 2
surviving patients subsequently underwent uneventful vascular surgery with
perioperative -blocker
administration for cardiac protection. The other 4 patients underwent
vascular surgery without prior myocardial revascularization and received -blockers for
cardiac protection. None of the other non-DECREASE patients received -blockers for
cardiac protection.
Dobutamine Stress Echocardiography
Dobutamine stress echocardiography was performed according to a standard
protocol.11 The left
ventricle was divided into 16 segments and wall motion was scored on a 5-point
ordinal scale (1, normal wall motion; 2, mild hypokinesis; 3, severe
hypokinesis; 4, akinesis; and 5, dyskinesis). The results of DSE were
considered positive if new wall-motion abnormalities (NWMAs) occurred (ie, if
wall motion in any segment worsened by 1
more grades during the test, with the exception of akinesis becoming
dyskinesis). The extent and location of ischemia were evaluated and a
wall-motion index was calculated, both at rest and during peak stress.
End Point Definition
The study end point was a composite of cardiac death or nonfatal MI (MI)
occurring during the period from screening until 30 days after surgery. An
adverse events committee adjudicated all end points. Deaths were considered
to be cardiac related unless there was explicit evidence for a noncardiac
cause. Myocardial infarction was defined by either a serum creatine kinase
level of more than 110 U/L with a myoglobin isoenzyme fraction of more than
10%, or by new Q waves faster than 30 milliseconds in duration on the 12-lead
electrocardiogram.
Data Analysis
Univariable and multivariable logistic regression analyses were applied to
evaluate the relations between a limited number of baseline clinical
characteristics, DSE results, -blocker therapy, and the composite end points as outlined above.
All variables that reached a P
value <.50 in univariable analysis entered the multivariable stage.
Multivariable models were constructed by backward deletion of the least
significant characteristics, applying the Akaike optimal information
criterion.12, 13 Special attention
was paid to the extent to which DSE results and -blocker therapy contributed to the prognostic information
obtained from clinical characteristics alone. Odds ratios (ORs) and
corresponding 95% confidence intervals (CIs) are reported.
Despite the fact that the population consisted
of patients undergoing high-risk surgery, the number of outcome events
appeared to be limited. Therefore, there was a serious concern that model
overfitting would occur. To overcome this, we limited the number of candidate
clinical variables to be included in the model, whereby, particularly, the
results of prior risk modeling analyses in surgical patients were considered.14-17 Furthermore, we
applied a clinical risk model that was developed elsewhere to our data set,
and collapsed the clinical risk assessment into 1 index variable.
Subsequently, the prognostic value of this risk index and the additional and
additive prognostic value of DSE results and -blocker therapy were analyzed by logistic regression analyses. We
chose the risk index that was recently developed by Lee and colleagues17 in a data set of
4315 patients undergoing major noncardiac surgery, including 898 patients
undergoing vascular surgery. To compose the Lee risk index, 1 point is
assigned to each of the following characteristics: high-risk type of surgery,
known ischemic heart disease, a history of congestive heart failure, a
history of cerebrovascular disease, diabetes mellitus, and renal failure.
The performance of the risk models was
determined by the cardiac index, which indicates how well a model rank-orders
patients with respect to their outcomes; the cardiac index ranges from 0.5
(not predictive at all) to 1.0 (optimal performance).18 In addition, the
Hosmer-Lemeshow statistic for goodness of fit is presented. The predictive
accuracy of the models was further evaluated by bootstrapping techniques.19 One hundred bootstrap
samples were drawn from the original data set (with replacement) and the full
modeling process, including the stepwise selection, was redone in every
bootstrap sample. The models developed in the bootstrap samples were
subsequently tested in the original data set. This process provides a factor
to correct for a possible overoptimism of the cardiac index.20
Based on the results obtained by the described
modeling strategies, a risk score was developed to estimate an individual
patient's risk of perioperative cardiac death or MI. Furthermore, a simple
decision-tree is constructed to help the physician decide in which patients
to refer for noninvasive perioperative cardiac testing.
RESULTS
The primary patient characteristics are
described in Table 1.
Obviously, patients receiving -blockers during surgery had a risk profile that was worse than
that of patients not taking such medication because they had higher rate of
hypertension, ventricular arrhythmias, and history of coronary disease.
Furthermore, patients receiving -blockers more frequently used other cardiac medications than those
who were not receiving -blockers. There
were 45 perioperative cardiac complications (3.3%): 31 patients had cardiac
death and another 14 nonfatal MI.
Univariable Models
In univariable analysis, a history of heart failure was the most significant
determinant of adverse cardiac outcome among the clinical variables examined
(Table 2).
The subgroup of patients with a history of heart failure (5% of the
population) had a more than 5-fold increase in the risk of perioperative
cardiac death or MI compared with those without such a history. Other
important univariable determinants of perioperative cardiac complications
were a history of MI, prior cerebrovascular accident (CVA), current or prior
angina pectoris, and age 70 years and older. Patients taking cardiac
medications had higher event rates than patients not taking such medication;
statistical significance was observed for nitrates and angiotensin-converting
enzyme (ACE) inhibitors. There was no relationship between the type of
surgery and the composite end point.
Patients who did not undergo DSE (ie, patients
without clinical cardiac risk factors) and those without NWMAs during DSE had
a significantly lower cardiac death or MI rate than patients with NWMAs
during DSE (0.4% and 1.6% vs 13.5%, respectively (P<.001; Table 3).
Thus, NWMAs were strongly predictive of adverse perioperative cardiac
outcome. Moreover, the extent of stress-induced ischemia also provided
important prognostic information, as the event rates ranged from 10.8% in
those with NWMAs in 1 to 4 segments to 23.9% in patients with NWMAs in 5 or
more segments. The echocardiogram at rest also provided prognostic
information. Patients with 5 or more abnormal segments had a 4- to 6-fold
increased risk of cardiac complications compared with those with a normal or
slightly aberrant (1-4 abnormal segments) wall motion at rest.
Despite their overall risk profile being worse
(Table 1),
patients receiving -blockers during
surgery had a significantly reduced risk of cardiac death or MI compared with
those not taking such medication. Among the 254 patients who did not undergo
DSE, no perioperative cardiac complications were observed in the 8.7% of
patients receiving -blockers,
whereas there was 1 event (0.4%) in the remaining patients. In the 875
patients without stress-induced NWMAs, 22% were receiving -blockers. One cardiac complication (0.5%) occurred in
this group, and there were 13 (1.9%) in those not receiving -blockers. Finally, in the 222 patients with NWMAs, 67% of
those receiving -blockers with
4.7% having a perioperative cardiac event vs 31.5% among those not receiving -blockers. There
was no evidence of a differential effect of -blocker therapy in these patient categories (homogeneity test for
ORs, P = .69), so that the
crude OR is best estimated by the method of Mantel-Haenszel test (0.1; 95%
CI, 0.1-0.3).
Multivariable Models
Many of the univariably significant clinical determinants of cardiac outcome
remained important in the multivariable analysis (Table 4).
After correcting for other determinants, prior CVA showed the strongest
relationship with perioperative cardiac complications. A history of heart
failure and prior MI were the next strongest clinical predictors. Angina and
age 70 years or more were also important. After correcting for differences in
clinical characteristics, patients receiving -blockers were still at significantly lower risk for the composite
end point than those who were not (adjusted OR, 0.3; 95% CI, 0.1-0.7).
When clinical data were combined with DSE
results, advanced age, angina pectoris, prior MI, and prior heart failure
lost most of their predictive power with respect to the composite end point.
In fact, DSE results (especially the presence or absence of NWMAs) were the
most important determinants of perioperative cardiac outcome. In connection
with both clinical data and DSE results, -blocker therapy was again associated with a significantly reduced
risk of the composite end point. The protective effect of -blocker therapy was observed in long-term users (OR, 0.1;
95% CI, 0.0-0.3) as well as in patients who received bisoprolol as part of
the DECREASE study (OR, 0.1; 95% CI, 0.0-0.4).
Application of the Lee Risk
Index
In all, 611 patients (45%) had a Lee risk index of 1, 509 (38%) had an index
of 2, and 231 (17%) had an index of 3 or more points (note that all patients
underwent high-risk surgery, and thus had a risk index 1 points). The incidence of the composite end point in these
patients was 1.3%, 3.1%, and 9.1% (P<.001).
Regression analysis revealed a crude OR of 2.3 for the composite end point
associated with a 1-point increase in the risk index (95% CI, 1.8-3.1).
Multivariable analyses again demonstrated the additional and additive
prognostic value of DSE results and -blocker therapy (Table 5).
Predictive Accuracy
The cardiac index for the composite end point model based on clinical
characteristics only was 0.78, reflecting good ability to discriminate
between patients who did and did not have a life-threatening cardiac
complication. The associated goodness of fit of the  27 statistic was 2.1 (P = .95). After correction for
overoptimism the cardiac index was 0.72, still reflecting satisfactory
performance. The multivariable model that combined clinical data with DSE
results had considerably better discriminating power with a cardiac index of
0.87 (goodness of fit 26
= 7.6, P = .27;
optimism-corrected cardiac index, 0.82). The cardiac index connected with the
Lee risk-index-alone model was 0.71 (goodness of fit 26, 7.0; P
= .32) and improved to 0.87 by adding DSE results and information regarding -blocker therapy.
Risk Classification Model
Based on the results described above, a simple scheme was developed to
estimate a patient's risk of perioperative cardiac complications (Figure 1).
A clinical risk score can be determined on the basis of the patient's age and
clinical history. If this risk score is in the range of 0 to 2 points (83% of
the patients belonged to this category) and the -blockers are administered perioperatively, the estimated
cardiac complication rate is relatively low (<2%), irrespective of the DSE
result. The estimated risk of cardiac complications is also low in patients
with a risk score of 3 or more points without NWMAs, provided -blockers will be applied. Patients with a risk score of 3
or more and NWMAs were at a considerable cardiac risk (>6%), despite -blocker therapy.
COMMENT
Consistent with other studies,14-17 our analysis of
1351 patients undergoing high-risk noncardiac vascular surgery demonstrated
that advanced age, current or prior angina, and a history of cardiac or
cerebral events are the most important clinical determinants of perioperative
cardiac death or MI. Apart from clinical data, DSE results were highly
predictive of adverse cardiac outcome, which also confirms other
investigations.1 Patients receiving -blockers had
significantly lower risk than those not receiving them. It should be
emphasized that patients receiving -blockers had a considerably worse overall risk profile than those
not receiving them, which makes this result even more convincing. The
additional and additive prognostic value of DSE results and -blocker therapy was confirmed in the analysis that
applied the previously developed Lee risk index. On the basis of a risk score
composed of a weighted sum of the prognostic clinical characteristics, a
large group (83%) of low-risk patients with a score of less than 3 could be
defined. In this group, the estimated risk of cardiac complications is less
than 1%, regardless of DSE results, as long as patients are receiving -blockers. In the
remaining patients, those without stress-induced ischemia also had a low
estimated cardiac risk in the presence of perioperative -blocker therapy.
Univariable analyses showed that patients with
diabetes mellitus, pulmonary disease, prior ventricular arrhythmias, or
aortic valvular stenosis are at increased risk of surgical complications.
However, in contrast to earlier studies,16, 21 these factors were
not independent predictors in our multivariable analyses. This finding can be
reflect a changing patient population or improved perioperative management
although it may also be a matter of (lack of) power. Additionally, it should
be emphasized that cardiac death or MI during complex surgery is most likely
to occur in patients with stress-inducible cardiac ischemia. Indeed, the
occurrence of NWMAs during DSE was a major determinant of adverse outcome.
Because a stress-induced ischemia was not more common in patients with
diabetes mellitus, pulmonary disease, prior ventricular arrhythmias, or
aortic stenosis (78 NWMAs of 352 cases [22%]) than in patients without such
characteristic (144 NWMAs of 745 cases [19%]; P = .28), these characteristics are likely not strong
determinants of a predisposition to ischemia. In contrast, patients with
prior MI, prior heart failure, or prior CVA were more likely to have
stress-induced ischemia than other patients (150 NWMAs of 545 cases [28%] vs
72 NWMAs of 552 cases [13%]; P<.001).
Still, factors such as diabetes mellitus, may be predictive of long-term
complications. Diabetes mellitus (and renal failure) were therefore still
incorporated in the clinical risk index (Figure 1).
Clinical Implications
Figure 2
may help to understand how results can be translated into clinical practice.
The perioperative cardiac event rate was low (1%) in patients with a clinical risk score of less than 3 points
and who were receiving -blockers. It
seems therefore appropriate to omit DSE (and other noninvasive cardiac
testing) in this large (>80%) group of patients and to proceed expeditiously
with surgery under protection by -blocker therapy. Dobutamine stress echocardiography is useful to
further risk-stratify patients with a clinical risk score of 3 or more
points. If protected by perioperative -blockade, patients without stress-induced ischemia still had a low
complication rate (2%) and are also candidates for prompt surgery. Patients
with a risk score of 3 or more points and NWMAs (approximately 6% of the
population) had a considerable complication rate despite the -blocker therapy. Our data suggest that the proposed
treatment policy in these patients may depend on the extent of stress-induced
ischemia. Although the numbers of patients and events are relatively small in
the specific subgroups, patients with NWMAs in 1 to 4 segments were properly
protected by -blockers. In
patients with more extensive ischemia, however, -blockers failed to reduce the rate of perioperative
cardiac complications. Cardiac catheterization and subsequent myocardial
revascularization should be considered in these patients.
The prescription of -blockers may delay surgery; so far, no study has
indicated what the optimal run-in period of this drug is in this setting.
Therefore, it can be questioned whether such therapy is really necessary in
patients at very low risk. In the group of patients with a risk score of 0
points, 1.2% perioperative complications were observed in those without -blocker therapy
(Figure 2).
This complication rate seems sufficiently low to refrain from administering
medication indeed and opt for surgery without delay. Another issue is that -blocker therapy
may be contraindicated, especially in patients with reactive airway diseases,
such as severe asthma or chronic obstructive pulmonary disease with a
reactive component. It should be noticed that these patients are rare: there
were no such cases in our data set. Still, if -blocker therapy is contraindicated, the use of calcium
antagonists with a negative chronotropic effect may be considered. The recent
Incomplete Infarction Trial of European Research Collaborators Evaluating
Prognosis post-Thrombolysis (INTERCEPT) study of post-MI patients reported
fewer cardiac events in patients randomized to such a drug compared with
placebo.22
Study Limitations
Because of its retrospective nature, our analysis has limitations, which
should be considered when interpreting the results. The risk-stratification
and modification scheme using a clinical risk score, DSE, and -blocker therapy was developed after events had occurred.
Furthermore, only some patients (those participating in the DECREASE study)
were randomized to receive either perioperative -blockers or standard care. Patient characteristics may have
played an important role in the decision to administer -blockers to patients who did not participate in the
DECREASE study and could potentially bias the results. Importantly, we found
no difference in the cardioprotective effect of -blockers between patients who were randomized within the
framework of the DECREASE study and those whose receipt of -blockers was chronic. This suggests that the utility of
perioperative -adrenergic
blockade extends beyond the small subset of high-risk patients who
participated in the DECREASE study. Finally, the observed event rates were
relatively low compared with previous investigations. It should be
appreciated that our results were obtained in selected, high-volume hospitals
(3 of the participating hospitals were university hospitals) and that cardiac
event rates might differ in other centers.
Conclusions
Dobutamine stress echocardiography effectively identifies patients at risk
for perioperative cardiac events. Besides, our data showed that the
additional predictive value of DSE is limited in clinically low-risk patients
receiving -blockers. This
observation may have important clinical implications: in a majority of
patients, additional testing by DSE can be avoided and patients can proceed
safely for surgery without delay. In a smaller group of clinically
intermediate- and high-risk patients, DSE may help to identify patients in
whom surgery can still be performed while receiving -blockers and those in whom cardiac revascularization
should be considered.
Author/Article
Information
Author
Affiliations: University Hospital Rotterdam, Rotterdam (Drs
Boersma, Poldermans, Steyerberg, van de Ven, van Urk, and Roelandt), the
University Hospital Leiden, Leiden (Dr Bax), and University Hospital Utrecht,
Utrecht (Dr Banga), the Netherlands; and University of Manitoba, Winnipeg (Dr
Thomson).
Corresponding
Author and Reprints: Don Poldermans, MD, PhD,
University Hospital Rotterdam, Department of Surgery, Room H921, Dr
Molewaterplein 40, 3015 GD Rotterdam, the Netherlands (e-mail: [log in to unmask]).
Author Contributions: Study concept and design:
Boersma, Poldermans, Roelandt.
Acquisition of data: Boersma, Poldermans.
Analysis and interpretation
of data: Boersma, Poldermans,
Bax, Steyerberg, Thomson, Banga, van de Ven, van Urk.
Drafting of the manuscript: Boersma, Poldermans.
Critical revision of the
manuscript for important intellectual content: Bax, Thomson, Banga, van de Ven, van Urk, Roelandt.
Statistical expertise: Boersma, Steyerberg.
Study supervision: Roelandt.
Members of the Dutch
Echocardiographic Cardiac Risk Evaluation Applying Stress Echocardiography
group are listed in
Poldermans D, Boersma E, Bax JJ, et al, for the Dutch Echocardiographic
Cardiac Risk Evaluation Applying Stress Echocardiography Study Group. The
effect of bisoprolol on perioperative mortality and myocardial infarction in
high-risk patients undergoing vascular surgery. N Engl J Med. 1999;341:1789-1794.
REFERENCES
1.
Poldermans D, Fioretti PM, Forster T, et al.
Dobutamine stress echocardiography for assessment of perioperative cardiac
risk in patients undergoing major vascular surgery.
Circulation.
1993;87:1506-1512.
MEDLINE
2.
Poldermans D, Arnese M, Fioretti PM, et al.
Improved cardiac risk stratification in major vascular surgery with
dobutamine-atropine stress echocardiography.
J Am Coll Cardiol.
1995;26:648-653.
MEDLINE
3.
Pellikka PA, Roger VL, Oh JK, Seward JB, Tajik AJ.
Safety of performing dobutamine stress echocardiography in patients with
abdominal aortic aneurysm > or = 4 cm in diameter.
Am J Cardiol.
1996;77:413-416.
MEDLINE
4.
Davila-Roman VG, Waggoner AD, Sicard GA, Geltman EM, Schechtman KB, Perez JE.
Dobutamine stress echocardiography predicts surgical outcome in patients with
an aortic aneurysm and peripheral vascular disease.
J Am Coll Cardiol.
1993;21:957-963.
MEDLINE
5.
Poldermans D, Bax JJ, Thomson IR, et al.
Role of dobutamine stress echocardiography for preoperative cardiac risk
assessment before major vascular surgery.
Echocardiography.
2000;17:79-91.
MEDLINE
6.
Lalka SG, Sawada SG, Dalsing MC, et al.
Dobutamine stress echocardiography as a predictor of cardiac events
associated with aortic surgery.
J Vasc Surg.
1992;15:831-840.
MEDLINE
7.
Langan EM, Youkey JR, Franklin DP, Elmore JR, Costello JM, Nassef LA.
Dobutamine stress echocardiography for cardiac risk assessment before aortic
surgery.
J Vasc Surg.
1993;18:905-911.
MEDLINE
8.
Poldermans D, Boersma E, Bax JJ, et al.
The effect of bisoprolol on perioperative mortality and myocardial infarction
in high-risk patients undergoing vascular surgery.
N Engl J Med.
1999;341:1789-1794.
MEDLINE
9.
Lee TH.
Reducing risk in noncardiac surgery.
N Engl J Med.
1999;341:1838-1840.
MEDLINE
10.
Mayet J, Wolfe J, Foale R.
Cardiac risk stratification [letter].
Lancet.
2000;355:500.
MEDLINE
11.
McNeill AJ, Fioretti PM, el-Said SM, Salustri A, Forster T, Roelandt JR.
Enhanced sensitivity for detection of coronary artery disease by addition of
atropine to dobutamine stress echocardiography.
Am J Cardiol.
1992;70:41-46.
MEDLINE
12.
Akaike H.
Information theory as an extension of the maximum likelihood principle.
In: Petrov BN, Csaki F, eds. Second
International Symposium on Information Theory. Budapest, Hungary:
Akademia Kiado; 1973:267-281.
13.
Boersma E, Pieper KS, Steyerberg EW, et al.
Predictors of outcome in patients with acute coronary syndromes without
persistent ST-segment elevation: results from an international trial of 9461
patients.
Circulation.
2000;101:2557-2567.
MEDLINE
14.
Mangano DT, Goldman L.
Preoperative assessment of patients with known or suspected coronary disease.
N Engl J Med.
1995;333:1750-1756.
MEDLINE
15.
Eagle KA, Brundage BH, Chaitman BR, et al, for the Committee on Perioperative
Cardiovascular Evaluation for Noncardiac Surgery.
Guidelines for perioperative cardiovascular evaluation for noncardiac
surgery: Report of the American College of Cardiology/American Heart
Association Task Force on Practice Guidelines.
Circulation.
1996;93:1278-1317.
MEDLINE
16.
L'Italien GJ, Paul SD, Hendel RC, et al.
Development and validation of a Bayesian model for perioperative cardiac risk
assessment in a cohort of 1,081 vascular surgical candidates.
J Am Coll Cardiol.
1996;27:779-786.
MEDLINE
17.
Lee TH, Marcantonio ER, Mangione CM, et al.
Derivation and prospective validation of a simple index for prediction of
cardiac risk of major noncardiac surgery.
Circulation.
1999;100:1043-1049.
MEDLINE
18.
Kendal DG.
Rank Correlation Methods.
London, England: Charles Griffin; 1962.
19.
Gong G.
Cross-validation, the jackknife, and the bootstrap: excess error estimation
in forward logistic regression.
J Am Stat Assoc.
1986;81:108-113.
20.
Van Houwelingen JC, Le Cessie S.
Predictive value of statistical models.
Stat Med.
1990;9:1303-1325.
MEDLINE
21.
Mangano DT.
Perioperative cardiac morbidity.
Anesthesiology.
1990;72:153-184.
MEDLINE
22.
Boden WE, van Gilst WH, Scheldewaert RG, et al, for the Incomplete Infarction
Trial of European Research Collaborators Evaluating Prognosis
post-Thrombolysis (INTERCEPT).
Diltiazem in acute myocardial infarction treated with thrombolytic agents: a
randomised placebo-controlled trial.
Lancet.
2000;355:1751-1756.
MEDLINE
|
