(Circulation. 1998;98:823-824.)
© 1998 American Heart Association, Inc.
Noncardiac Surgery in CAD Patients
Enrique V. Carbajal, MD
Veterans Affairs Medical Center Fresno, Calif
To the Editor:
The article by Eagle et al1 provides interesting
data that may have important implications in the management of patients
with coronary artery disease (CAD) who are scheduled for
noncardiac surgery. This is an extremely interesting and complex
subject, in part because of the difficulty in assessing cardiac risk in
CAD patients and because of the paucity of data to guide management
strategies aimed at reducing the risk of perioperative
cardiac complications.
Indeed, there is an urgent need for management tactics in CAD patients
to reduce or suppress perioperative coronary
events (myocardial infarction [MI] or cardiac death). In this regard,
the authors accomplished a superb task in summarizing data from the
CASS trial.1,2
There are, however, some issues of concern in this report. The data
presented in this study1 appear to be
derived from retrospective observations in patients from the CASS
registry and randomized groups3 who underwent
noncardiac surgeries. In the design of CASS, a portion of patients from
the registry were randomized to treatment according to specific
clinical and angiographic criteria.3 Because
treatment of CAD was dictated by physician and patient
preference,1 it is likely that significant bias
was introduced into the various analyses of treatment outcomes.
It appears unlikely that use of various statistical tools while these
data are evaluated will compensate for the observational nature of the
analyses.
It is interesting to note that in the high-risk noncardiac surgery
groups (vascular, thoracic, and head and neck), patients without
evidence of CAD had higher rates of perioperative MI
than did CAD patients with prior CABGs. In such patients, one would
expect the opposite findings.
To help explain the reported findings on outcome, one should consider
the available medical therapy options at the time of the start of and
follow-up of CASS.3 Medical therapy was based on
administration of sublingual nitroglycerin, isosorbide
dinitrate, and nitroglycerin
ointment.3 The use of propranolol was
suggested but not closely monitored. The decision to prescribe a given
treatment was left to the referring and treating physicians. Similarly,
management of risk factors was suggested, and enforcement of these
interventions was left to the discretion of the treating physician.
Therefore, there was a rather limited effort, based on the prevailing
clinical practice, to provide optimal
antianginal–anti-ischemic medical therapy or to furnish
supervised intensive risk factor modification aimed at
"stabilizing" coronary plaques. More aggressive medical
intervention could have contributed to a better outcome among patients
without prior CABG.
The authors have highlighted several important points, such as
identifying specific procedures associated with higher risk of MI or
death. It was also suggested that the higher-risk subcategory of
patients undergoing noncardiac procedures may derive the benefit, if
any, from prior CABG.
The stimulating suggestions from this study1
should be evaluated in large, prospective, randomized studies using
optimal myocardial revascularization and medical
therapies. Only after such trial(s) are completed will definitive data
be available to assist the clinician in making a recommendation for
myocardial revascularization or intensive medical
therapy in stable CAD patients scheduled for noncardiac surgery.
References
1.
Eagle KA, Rihal CS, Mickel MC, Holmes DR, Foster ED,
Gersh BJ, for the CASS Investigators and University of Michigan Heart
Care Program. Cardiac risk of noncardiac surgery: influence of
coronary disease and type of surgery in 3368 operations.
Circulation. 1997;96:1882–1887.[Abstract/Free Full Text]
2.
Foster E, Davis K, Carpenter J, Abele S, Fray D. Risk
of noncardiac operation in patients with defined coronary
disease: the Coronary Artery Surgery Study (CASS) registry
experience. Ann Thorac Surg. 1986;41:42–50.[Abstract]
3.
The principal investigators of CASS and their
associates. The National Heart, Lung, and Blood Institute
Coronary Artery Surgery (CASS). Circulation.
1981;63(suppl I):I-1–I-81.
Response
Kim A. Eagle, MD;
Charanjit S. Rihal, MD;
Mary C. Mickel, MS;
David R. Holmes, MD;
Eric D. Foster, MD;
; Bernard J. Gersh, MD
University of Michigan Heart Care Program,
Ann Arbor, Michigan
Dr Carbajal raises concerns regarding our recent article
discussing the cardiac risk of noncardiac surgery in patients followed
up after enrollment in CASS.1 Dr Carbajal
correctly notes that because the majority of patients in this study
were not actually randomized in CASS, it is conceivable that there was
bias in terms of the physician or patient preference for or against
CABG surgery. However, in the case of CASS, if anything there may have
been a tendency for nonrandomized patients to be directed toward
surgery when they had more advanced coronary disease, not less.
This is evident in our Table 3, which indicates that a much greater
percentage of patients who ultimately had bypass surgery had 3-vessel
disease compared with those treated medically. This tendency for
patients with more advanced coronary disease to receive bypass
surgery, if anything, should have biased the analysis against
CABG in terms of effectiveness in reducing
perioperative and long-term risk.
Dr Carbajal also states that patients having no CAD had higher event
rates after high-risk noncardiac surgery than those treated previously
with bypass surgery. This is not true. The Figure in our article
demonstrates that the perioperative MI rate among
patients without coronary disease was 0.8%, identical to
patients who had CABG surgery before noncardiac surgery. In fact, the
death rate showed a trend to be higher (1.7% versus 1%) in patients
who had CABG than in patients with no coronary disease. Because
of small numbers in the subsets of high-risk surgery, there is random
variation, but the overall numbers suggest that prior successful CABG
surgery returns patients toward a level of risk that is similar to but
not lower than individuals without significant CAD.
Finally, Dr Carbajal correctly points out the most important
limitations in this analysis. These were highlighted in our
article under the limitations section. Because medical management,
coronary surgery, and coronary angioplasty are evolving
rapidly, it is difficult to know how to frame results from patients
treated in the 1980s with those being managed in the late 1990s. As
Carbajal suggests, one way of trying to resolve remaining questions
would be the performance of a randomized trial. We described
such a trial in an editorial several years ago.3
Currently, a pilot phase of a trial examining the influence of medical
therapy versus revascularization in these patients
is under way in the Veterans Affairs system. Although a similar trial
has been proposed to the National Institutes of Health, this
project has not received sufficient prioritization to be funded.
Part of the funding concerns for this trial are due to the very large
numbers and long-term follow-up that would be required to develop a
satisfactory answer. Because the short-term risks of coronary
revascularization for many patients can only be
overcome by long-term benefit, any trial designed to study patients
isolated to the perioperative period is not likely to
show a benefit from revascularization.
References
1.
Eagle KA, Rihal CS, Mickel MC, Holmes DR, Foster ED,
Gersh BJ, for the CASS Investigators and University of Michigan Heart
Care Program. Cardiac risk of noncardiac surgery: influence of
coronary disease and type of surgery in 3368 operations.
Circulation. 1997;96:1882–1887.
2.
Domanski M, Ellis S, Eagle K. Does preoperative
coronary revascularization before
noncardiac surgery reduce the risk of coronary events in
patients with known coronary artery disease? Am J
Cardiol. 1995;75:829–831.[Medline]
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