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Ann Thorac Surg 2006;82:795-801
© 2006 The Society of Thoracic Surgeons
a Departments of Surgery and Cardiology, VA Medical Center and University of Minnesota, Minneapolis, Minnesota
b The Cooperative Studies Program Coordinating Center and the Division of Peripheral Vascular Surgery, VA Hospital, Hines, Illinois
c Division of Cardiology, VA Medical Center, Portland, Oregon
d Division of Cardiology, VA Medical Center, Tucson, Arizona
e Division of Vascular Surgery, VA Medical Center, Denver, Colorado
Accepted for publication March 23, 2006.
* Address correspondence to Dr Ward, VA Medical Center (112), One Veterans Dr, Minneapolis, MN 55417 (Email: wardx020{at}umn.edu).
Presented at the Forty-second Annual Meeting of The Society of Thoracic Surgeons, Chicago, IL, Jan 30–Feb 1, 2006.
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Abstract |
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 Top Abstract IntroductionPatients and MethodsResultsCommentDiscussionFootnotesAcknowledgmentsReferences |
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METHODS: In this Veterans Affairs Cooperative trial involving 18 medical centers, 222 patients underwent elective vascular surgery after coronary revascularization. The mode of coronary revascularization was selected at each site by the local investigators (CABG in 91 patients and PCI in 131 patients). The vascular surgical indications were similar in both groups.
RESULTS: There were 2 deaths in the CABG group (2.2%) and 5 deaths in the PCI group (3.8%; p = 0.497) after the vascular procedure. There were fewer perioperative myocardial infarctions after the vascular operation in CABG patients (6.6%) than in PCI patients (16.8%; p = 0.024), despite more diseased vessels in the CABG group (3.0 ± 1.3 versus 2.2 ± 1.4, respectively; p < 0.001). The completeness of revascularization (defined as the number of coronary artery vessels revascularized relative to the total number of vessels with a stenosis 
70%) in patients in the CABG and PCI groups was 117% ± 63% and 81% ± 57%, respectively (p < 0.001). Hospital length of stay in CABG versus PCI patients was 6 (4, 8) and 7 (4, 10) days, respectively (p = 0.078).
CONCLUSIONS: Among patients receiving multivessel coronary artery revascularization as prophylaxis for elective vascular surgery, patients having a CABG had fewer myocardial infarctions and tended to spend less time in the hospital after the vascular operation than patients having a PCI. More complete revascularization accounted for the intergroup differences.
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Introduction |
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TopAbstractIntroductionPatients and MethodsResultsCommentDiscussionFootnotesAcknowledgmentsReferences |
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A perioperative myocardial infarction may reduce the long-term survival after vascular surgery [2, 3]. Therefore, there is a need to understand differences in perioperative outcomes associated with noncardiac operations between patients who have undergone prophylactic coronary artery bypass grafting (CABG) versus percutaneous coronary intervention (PCI). The Bypass Angioplasty Revascularization Investigation (BARI) trial randomized patients to CABG versus PCI and reported comparable rates of perioperative myocardial infarctions in those patients undergoing noncardiac surgery [4]. The interpretation of that substudy may be difficult because the median interval between coronary revascularization and noncardiac surgery was 29 months. Any decision to undergo prophylactic CABG or PCI must consider the timeliness of the reference operation. In this substudy of the CARP trial, we studied the effect of prophylactic coronary revascularization on the incidence of perioperative myocardial infarction during vascular surgery. We hypothesized that CABG is associated with fewer perioperative myocardial infarctions when compared with PCI and that the completeness of coronary revascularization can account for those differences.
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Patients and Methods |
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TopAbstractIntroductionPatients and MethodsResultsCommentDiscussionFootnotesAcknowledgmentsReferences |
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The study design and results of the original randomized CARP trial have been previously published [1, 5]. In brief, patients were considered eligible for the study if they were scheduled for an elective vascular operation for either an abdominal aortic aneurysm or lower extremity arterial occlusive disease. Coronary angiography was recommended if the patient was considered to be at high risk for significant coronary artery disease. If coronary angiography revealed significant flow-limiting disease (one or more of the major coronary arteries had a stenosis 70% that was suitable for revascularization), the patient was eligible for randomization. Of the 510 patients who were randomized, 258 were assigned to prophylactic coronary revascularization and 252 to no revascularization before the reference vascular operation.
The decision to perform either PCI or CABG was left to the discretion of the local investigators. If PCI was planned, it was advised that the vascular operation be delayed to avoid the increased risk of in-stent thrombus [6]. The potential long-term advantage of CABG versus PCI among patients with diabetes and multivessel disease was also considered in the decision. After vascular surgery, blood for cardiac enzymes and an electrocardiogram were collected each day for 4 days and assessed by the local sites for the presence of a perioperative myocardial infarction. A myocardial infarction after vascular surgery was defined by an elevation of the locally measured cardiac enzymes above the normal reference value [7]. The assays used for local determination of myocardial infarction were troponin I or troponin T at the majority of sites. An end point committee, independent of the CARP investigators, reviewed all source documents, confirmed all perioperative myocardial infarctions, and determined all causes of death. Long-term survival was determined from the time of the vascular operation until the end of the study and was retrieved through the BIRLS system (the VA Beneficiary Information and Records Locator Subsystem).
The completeness of revascularization was defined as the number of coronary artery vessels that were revascularized relative to the total number of vessels with a stenosis of 70% or greater. The vessels that were considered from the angiographic report to be potential target vessels included the left anterior descending coronary artery, circumflex artery, right coronary artery, ramus intermedius, three diagonal branches, three obtuse marginal branches, the right and left posterior descending and posterolateral branches. Of the potential 13 distal vessels with stenoses of 70% or greater, the completeness of revascularization was determined by the number of vessels revascularized relative to the number of vessels diseased. A revascularization rate greater than 100% could be obtained if one of the three major vessels had more than one revascularization site or if vessels with stenoses less than 70% were revascularized.
Data are expressed as proportions, means and standard deviations, or medians with interquartile range when specified. The 
2 test was used to compare categorical data and the Student's t test or Wilcoxon rank-sum test, when appropriate, was used to compare continuous variables. Survival distributions were compared by the log-rank test. Three separate multivariate logistic regression models were run to estimate the effect of type of revascularization on postvascular surgery myocardial infarction after adjusting for the effect of covariates. These three models adjusted for completeness of revascularization, time between revascularization and the vascular procedure, and type of vascular surgery. Odds ratios and 95% confidence intervals are reported from these models. All tests were two-sided, and differences were considered significant at a probability value less than 0.05.
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Results |
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TopAbstractIntroductionPatients and MethodsResultsCommentDiscussionFootnotesAcknowledgmentsReferences |
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Comment |
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TopAbstractIntroductionPatients and MethodsResultsCommentDiscussionFootnotesAcknowledgmentsReferences |
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One should bear in mind that the original CARP trial was not designed to test the benefit of CABG versus PCI before a vascular operation [1]. Once a patient was assigned to preoperative coronary artery revascularization, the decision to perform CABG versus PCI was left to the discretion of the local investigators. Under the circumstances, we cannot eliminate potential confounding variables in that selection process that may have altered perioperative cardiac events. These variables include but are not limited to selection bias related to the suitability of targets and patient characteristics that would predict a more favorable recovery.
The advantage of performing CABG versus PCI as prophylaxis before noncardiac surgery has not been addressed in any previous study. A noncardiac operation after a CABG procedure is typically delayed to allow sufficient time for the patient to recover from the major insult of a sternotomy and cardiopulmonary bypass. There is no contraindication to performing a noncardiac operation immediately after a CABG, but this may not be the case immediately after PCI.
Among patients undergoing PCI, there is a risk of catastrophic outcomes during noncardiac operations when the surgery occurs within the first 2 weeks after deployment of a coronary stent [6]. In 40 consecutive patients, seven myocardial infarctions, 11 major bleeding episodes, and 8 deaths were reported with early operations [11]. All deaths and myocardial infarctions occurred when the noncardiac surgery took place within 14 days of the PCI. Of the 27 patients who had noncardiac surgery within 3 weeks of PCI, 6 of 7 had antiplatelet therapy discontinued before the vascular operation. These patients died by a mechanism that was suggestive of in-stent thrombosis. In contrast, only 1 of 20 patients died when antiplatelet therapy was continued during the operation, and no excessive bleeding episodes were noted in that group. In a similar study, most major adverse cardiovascular events were observed when noncardiac surgery was performed within 6 weeks of PCI [12]. As with other series, there were no cardiac events if the surgery was delayed for more than 42 days after the revascularization.
We believe that the higher incidence of perioperative myocardial infarctions in the PCI group reported in our study was not related to inappropriate timing of the vascular operation after revascularization [13]. The distribution of operations after PCI and CABG was similar, and there were few myocardial infarctions when the operations occurred early after the PCI. Many sick patients with severe lower limb ischemia required an urgent operation after coronary revascularization. These procedures tended to be infrainguinal in location. In this scenario, it was routine for the vascular surgeon to continue antiplatelet medications during the vascular operation. In patients undergoing either PCI or CABG, the continued use of antiplatelet therapy may have averted early stent or graft thrombosis.
In our cohort, the incidence of a myocardial infarction increased with increasing delay between coronary revascularization and the vascular procedure This increase may be attributed to the type of the vascular surgery. Prior studies have shown that the incidence of a perioperative myocardial infarction is increased during abdominal operations on the aorta [14, 15]. During abdominal vascular procedures the aorta is clamped. There is a resultant dramatic increase in cardiac work. Abdominal procedures also exhibit more extensive fluid shifts and altered hemodynamic variables compared with infrainguinal procedures. When abdominal operations were planned, many of the patients in our cohort had a delay in the procedure after either CABG or PCI. Alternatively, the higher incidence of myocardial infarctions observed with long delays may raise the question of loss of cardioprotection beyond a critical window after coronary revascularization. This may be related either to accelerated restenosis after PCI or early graft failure after CABG. It should be noted that most vascular surgeons discontinued the use of antiplatelet medications for 3 to 7 days before major abdominal procedures.
We used multivariate logistic regression analysis on the effect of abdominal procedures, timing of the vascular operation, and completeness of revascularization to analyze the reason for the increase in myocardial infarctions observed in the PCI group (Table 3). We observed that the completeness of coronary artery revascularization was the predominant variable accounting for the differences in perioperative myocardial infarctions between CABG and PCI. These data are consistent with the findings from the Arterial Revascularization Therapies Study trial, which showed that differences in cardiac events 1 year after revascularization with CABG versus PCI could be explained by completeness of revascularization [16].
The findings from our study are at slight variance with a substudy of the BARI trial, which showed no differences in the rates of perioperative myocardial infarctions between the patients who had been randomized to PCI versus CABG [4]. The intent of the revascularization procedure in the BARI trial was for relief of cardiac symptoms and not for the prevention of cardiac events during noncardiac surgery. As a result, the timing of the noncardiac operation occurred at a median of 29 months after the coronary revascularization procedure. This is a much longer interval than might be expected if the goal of treatment is to prevent perioperative cardiac events. Although the incidence of a perioperative myocardial infarction in our cohort was higher than that of the BARI substudy, our definition of cardiac events was more rigorous. In the BARI trial, a myocardial infarction was defined as an elevation of the cardiac biomarker to twice normal in association with electrocardiographic changes. In our cohort, a myocardial infarction was diagnosed by any elevation of a cardiac biomarker above normal [7].
On the basis of this study and the CARP trial, reasonable recommendations can be made to referring cardiologists, interventional cardiologists, vascular surgeons, and cardiovascular surgeons about the need for and timing of coronary revascularization procedures as prophylaxis for vascular operations [1]. In brief, the CARP investigation would suggest that patients in need of a vascular operation who have stable cardiac disease should proceed with that operation without coronary revascularization. This would be an acceptable strategy only if aggressive medical therapy with ß-blockers, antiplatelet drugs, and perhaps statins was used in the perioperative period [8–10]. In patients with both unstable coronary and vascular systems, either CABG or PCI would be acceptable if the vascular operation could be delayed beyond 6 weeks and antiplatelet drugs continued (infrainguinal procedures). When both systems are unstable and an abdominal procedure is anticipated, CABG would be the preferred mode of coronary revascularization.
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Discussion |
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TopAbstractIntroductionPatients and MethodsResultsCommentDiscussionFootnotesAcknowledgmentsReferences |
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DR WARD: In the slide concerning the timing of the vascular operation, most of the urgent procedures were in sick patients with lower extremity ischemia or threatened limb loss, and the procedure may have been performed within the same hospitalization as the myocardial revascularization. There was not an increased incidence of MI (myocardial infarction) at this point. There was, however, an increased incidence of death. As this result was measured in the combined groups, we did not have statistical power to look at the differences between those groups.
DR FRANK W. SELLKE (Boston, MA): You mentioned that the incomplete revascularization occurred more commonly in the PCI group than the CABG (coronary artery bypass grafting) group. What criteria did the cardiologists use to perform PCI? Did they not intend to perform a complete revascularization? Did they just do what they felt was technically possible?
DR WARD: Our trial was to test what we felt was an honest clinical strategy that was used by practitioners at the 18 different VA medical centers. We did not give them any instructions as to what they could do other than remind them that diabetic patients with multivessel disease may do better with CABG than PCI and that vascular operations occurring within 2 weeks of stent deployment have a higher risk of stent thrombosis if antiplatelet medications are stopped. The final decision for the type of revascularization procedure and suitability of vessels to revascularize was clinically based and left to the discretion of the local investigators.
DR DAVID J. UNDERHILL (Farmington, CT): Was any functional testing done to test for ischemia in these patients after their coronary revascularization before they had their surgical procedure? In other words, how was completeness of revascularization assessed?
DR WARD: One of the most important aspects of the execution of this trial was that patients were managed after randomization according to routine clinical practice. Unless a clinically unstable cardiac condition is observed after revascularization, no additional testing is clinically warranted before the vascular operation. We must remember that proceeding with a timely vascular operation was the intent of the physicians.
DR UNDERHILL: So how do you know there was a more complete revascularization if you didn't test for ischemia?
DR WARD: This is a fair question but beyond the scope of our study design. In clinical medicine it is not routine to consider the success of revascularization after uneventful procedures and that strategy was operational within this trial. We based our interpretation of completeness of revascularization on the number of arteries revascularized by either method as a percent of the number of coronary arteries that had stenosis greater than 70%.
DR G. HOSSEIN ALMASSI (Milwaukee, WI): I enjoyed your presentation. These are the patients that apparently were worked up for a planned peripheral vascular operation and then as part of that they had a cardiac workup to see if they were suitable for the peripheral vascular procedure. Was carotid artery disease part of these patients' planned surgery? That is one question. And second, based on these data, what are we going to do now for the patients that are going to have a vascular procedure and then the vascular surgeons say we have to fix their hearts first? What are your recommendations?
DR WARD: I think the next study will be in patients with carotid artery disease. We debated including these patients in our executive committee many, many, many times, and we felt that it would confuse the issue too much to do that during this trial. Patients with active cerebral vascular symptoms were not eligible for randomization.
As to your second question, I really believe in the CARP trial that was published in the New England Journal of Medicine. Coronary artery disease was a secondary problem in these patients, and we should have more confidence in medical therapy at the time of the needed vascular operation. Those therapies include antiplatelet medication, ß-blockers, and possibly statins. Perhaps we, the cardiovascular community, should deemphasize a strategy of widespread coronary revascularization procedures before elective vascular operations and place more emphasis on risk factor modification in the postvascular surgery period.
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Acknowledgments |
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Footnotes |
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TopAbstractIntroductionPatients and MethodsResultsCommentDiscussionFootnotesAcknowledgmentsReferences |
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