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From the Division of Cardiology, VA Medical Center, University of Minnesota, Minneapolis, Minnesota.
Address correspondence and reprint requests to Dr. Edward O. McFalls, MD, PhD, Division of Cardiology, VA Medical Center, University of Minnesota, Minneapolis, MN. Address e-mail to mcfal001{at}umn.edu.
Practicing anesthesiologists are frequently confronted with the difficult task of risk-stratifying patients just before a high-risk noncardiac operation. Overall, elective surgical procedures in a population of general medical patients without cardiac symptoms carry a very low risk of perioperative cardiac complications and, therefore, probably need no adjunctive testing.1 As discussed in the comprehensive review by Kertai,2 however, patients undergoing vascular surgery have a frequent prevalence of atherosclerotic heart disease and coupled with the complex hemodynamic stresses associated with aortic and arterial procedures, require special attention in the preoperative period. Coronary artery disease remains the major cause of death after any vascular operation and, therefore, consideration for preoperative coronary artery revascularization has been a justifiable endeavor.
PREOPERATIVE CORONARY ARTERY REVASCULARIZATION AND LONG-TERM OUTCOMES
Kertai's review focused on three studies that address the potential role of preoperative coronary artery revascularization in patients undergoing elective vascular surgery. The Coronary Artery Revascularization Prophylaxis (CARP) trial was the first multicenter, randomized study to test the hypothesis that coronary artery revascularization before major elective vascular surgery improves outcome in patients with documented coronary artery disease that is amenable to revascularization with either percutaneous coronary intervention or bypass surgery. Long-term survival was the primary end-point of the study and, at a median of 2.7 yr after randomization, was 78% in patients assigned to preoperative revascularization and 77% in patients assigned to conservative treatment (Relative Risk, 0.98; 95% Confidence Interval, 0.70–1.37; P = 0.92).3 By study design, those individuals who were selected for preoperative coronary angiography demonstrated increased clinical risk factors, either because of multiple intermediate risk variables or myocardial ischemia on a preoperative stress imaging test.4 Although a preoperative stress imaging test was not a prerequisite for enrollment into the study, 74% of the randomized cohort would have been deemed high clinical risk by the American College of Cardiology/American Heart Association (ACC/AHA) Guidelines, either because of the presence of multiple intermediate clinical risk variables or a high-risk stress-imaging test.5 Therefore, the CARP study results should be considered generalizeable to the vast majority of patients who have documented coronary artery disease and have been scheduled for elective vascular surgery. As one might expect, a strategy of preoperative coronary artery revascularization was not associated with a successful outcome in all end-point measures. Twice as many people failed to return for their needed vascular operation and, of those who did return, the delay from randomization to surgery was three times longer compared with the conservatively treated group (median of 54 days versus 18 days). Coupled with the increased expenditures associated with revascularization therapies and the lack of efficacy in either the short-term or long-term, widespread identification and treatment of fixed obstructive coronary artery disease in patients scheduled for elective vascular surgery is hardly an encouraging strategy. An additional consideration is that drug-eluting stents were not used during the CARP enrollment period yet have rapidly gained acceptance as the device of choice within most catheter laboratories. Accordingly, the associated delays in the present era are likely to be much greater than estimated from the CARP trial, with the uncertain risks of nonfatal myocardial infarctions after stopping antiplatelet drugs in the perioperative period. In the final interpretation of the CARP trial, it is imperative to understand that β-blockers were used in >85% of the randomized cohort before and after vascular surgery and highlight the evidence that conservative therapy with this class of drugs is more than just a placebo effect.6,7
Although the CARP trial supports a conservative approach in patients scheduled for elective vascular surgery, the trial was not designed to assess the optimal screening test for all patients with increased risk who are being considered for noncardiac operations. To address the utility of screening before elective surgery, the second article discussed in Kertai's review comes from Landesberg et al. who compiled an elegant review of their own institutional experience on preoperative stress thallium testing as a means of prognosticating long-term postoperative outcomes. Among patients with a high-risk preoperative thallium result, individuals who had successful coronary artery revascularization had an improved 3-yr survival after vascular surgery, compared with individuals of equivalent intermediate clinical risk scores who were not selected to undergo revascularization.8 The authors have suggested that the prevalence of multivessel disease was higher in their cohort compared with the CARP trial and speculate that the improved outcomes with preoperative revascularization reflect differences in anatomical risk. In defense of this position, by study design, patients with an unprotected left main stenosis 
50% were excluded from randomization into the CARP trial.4 Although this could explain some differences between studies, a severe left main stenosis was identified in only 48 of 1048 (4.6%) patients screened for the CARP trial9 which is not sufficient to account for the larger outcome differences between studies.
An alternative interpretation of the observed survival benefit with preoperative coronary artery revascularization after high-risk thallium tests is the potential selection bias that may occur with retrospective analyses. A comparison between those patients who were selected for preoperative revascularization and who returned for the vascular operation may result in the "survival of the fittest," when compared with those patients who were not selected for either coronary angiography or revascularization and proceeded directly to vascular surgery. Within the CARP registry, 1525 (34.5%) of 4414 screened patients were excluded from the randomization process by design, because of the presence of one or more severe comorbid conditions or an urgent vascular operation.10 These individuals had a frequent prevalence of clinical cardiac risk variables and a long-term risk of death that was 2.5 times higher than low-risk registry patients, yet they were not considered suitable candidates for preoperative coronary angiography and complex revascularization therapies. It is conceivable that these patients could have had high-risk preoperative thallium test results, yet inconceivable that they should have been exposed to excess cardiac procedures prior to surgery, considering their associated noncardiac conditions. Although Landesberg et al. have provided important prognostic information about postoperative outcomes in patients with high-risk thallium tests, until recently, it remained a testable hypothesis that preoperative revascularization improves outcomes in this highest risk cohort.
To address the optimal treatment in the highest risk group of patients being considered for vascular surgery, the final study discussed in the review was the Decrease V pilot study from Erasmus Medical Center in Rotterdam. The investigators in this trial enrolled patients with a high-risk stress imaging test before vascular surgery and randomized them to a strategy of preoperative revascularization or no revascularization prior to the scheduled vascular surgery.11 The prevalence of advanced coronary artery disease including three-vessel disease and unprotected left main disease was high and, therefore, addressed the potential limitations of a lower risk group of patients within the CARP trial. The results showed that, at 1 yr after surgery, the composite end-point of death and nonfatal myocardial infarction was not different between groups and provide complementary evidence that a strategy of preoperative revascularization before elective vascular surgery does not improve long-term outcomes.
TRANSLATING RANDOMIZED TRIALS INTO COMMON PRACTICE
Based on the ACC/AHA Guidelines, major risk variables should be identified before any elective noncardiac operation and these include unstable coronary syndromes, decompensated congestive heart failure, a severe valvular abnormality and life threatening arrhythmias.5 Patients with these risks were never included in the major randomized trials and their outcomes after noncardiac surgery were likely influenced by the unstable cardiac status. Among the vast majority of patients who do not have evidence of unstable cardiac signs or symptoms, however, we have come closer to accepting the concept that widespread screening with preoperative cardiac imaging tests will likely delay treatment of the primary vascular condition, without assurance of any improved outcome measure. It is time for clinicians to shift the emphasis from indiscriminate "pre-ops" with widespread cardiac imaging to adoption of evidence-based therapies including β-blockers, statins and antiplatelet drugs that preserve survival and quality of life while conserving valuable medical resources.
Footnotes
Accepted for publication October 22, 2007.
REFERENCES
This article has been cited by other articles:
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  P. Tinits Preoperative Coronary Revascularization in High-Risk Patients Undergoing Vascular Surgery Anesth. Analg., October 1, 2008; 107(4): 1442 - 1442. [Full Text] [PDF]
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