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Ann Thorac Surg 2006;81:1949-1957
© 2006 The Society of Thoracic Surgeons
Division of Cardiothoracic Surgery, Department of Surgery, Emory University School of Medicine, Atlanta, Georgia
* Address correspondence to Dr Guyton, Section of Cardiothoracic Surgery, The Emory Clinic, 1365 Clifton Rd, Atlanta, GA 30322 (Email: robert_guyton{at}emoryhealthcare.org).
| During the past 36 months, the author has received research grants, consultation fees/honoraria, and travel expenses from US Surgical Corporation, Guidant, Quest Medical, Medtronic, and Chase Medical. He has no investment interest in any of these corporations.
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| Abstract |
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The utilization of coronary artery bypass surgery (CABG) for revascularization of patients with coronary artery disease has been the subject of extensive scrutiny for more than a quarter century, beginning with randomized trials of CABG versus medical therapy conducted in the late 1970s [1]. Percutaneous intervention (PCI) for coronary revascularization has improved and has been used progressively more frequently compared with CABG, proponents of PCI claiming equivalent survival with a strategy of initial PCI compared with a strategy of initial CABG. Improvement in restenosis with drug-eluting stents has accelerated the utilization of PCI in patients with multivessel disease (MVD) [2].
This analysis of recent publications will examine the studies comparing CABG with PCI and combine this evidence with studies comparing bare metal stents and drug-eluting stents. This combination presents compelling evidence that CABG as initial therapy is superior to initial PCI with drug-eluting stents in the treatment of patients with MVD. The accelerated application of PCI to patients with MVD is not warranted. More importantly, patients are not being given adequate information about relative survival outcomes.
| Survival Advantage of CABG Compared With Medical Therapy for Patients With MVD |
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These trials of CABG versus medical therapy are the basis for current recommendations for the use of CABG for extension of survival in patients with MVD. Major improvements in medical therapy have occurred in the last 25 years, but these improvements apply to surgical patients as well as to medically treated patients. These trials are also the underpinning of inferences that PCI extends survival, based upon comparative studies of PCI versus CABG.
| Comparative Studies of PCI Versus CABG |
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The largest randomized controlled trial of CABG versus PCI in MVD was the Bypass Angioplasty Revascularization Investigation (BARI) trial, conducted in 18 centers from 1988 to 1991. An analysis of enrollment was published by Bourassa and colleagues [6]. A total of 25,200 patients with MVD was screened. Approximately half were excluded for clinical, administrative, or major angiographic reasons (eg, left main stenosis). The analysis states: "Of 12,530 patients who met clinical eligibility for BARI, 67% were unsuitable for one or both procedures. In < 95% of the time this was due to technical unsuitability for PTCA. Although complete revascularization was not a requirement, the protocol called for anticipation of successful relief of the major areas of ischemia. To leave patients with large areas of unrevascularized myocardium was clearly not in the patient's best interest" [6]. In all, 1,829 patients entered the trial. Mean age was 61 years; 59% had two-vessel disease and 41% had three-vessel disease [7]. Only 7.3% of screened MVD patients were randomized [6]. At 7 years, there was a significant survival advantage for CABG versus PCI (absolute survival difference 2.5%, relative survival difference 15%; p = 0.043, Fig 1) [8]. This significant 15% relative survival advantage for CABG occurred in the 7.3% of MVD patients screened in BARI who were most suitable for either procedure.
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Results from other trials of CABG versus PCI in MVD, in aggregate, are consistent with the result from the BARI trial. A meta-analysis of nine randomized controlled trials of CABG versus PCI in MVD revealed that survival was equivalent in these selected randomized patients at 1 year and 3 years, but initial CABG compared with initial PCI had a significant survival advantage at 5 years and 8 years (Figs 2 and 3)
[10].
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| Rapid Evolution of Revascularization Technology |
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An equally strong argument can be made that the quality and efficacy of CABG improved in the early 1990s. Weintraub and associates [11] at Emory examined outcomes and costs from 12,200 CABG patients from 1988 to1996. Multiple risk factors were significantly increased: age, prior coronary artery bypass, diabetes mellitus, prior myocardial infarction, class III or IV angina, congestive heart failure, hypertension, multivessel coronary disease, and low ejection fraction. Despite increased severity of disease, multiple outcome variables improved. Notably, operative mortality decreased from 4.7% to 2.7%. Accounting for the increased severity of patients, this was a 10% decrease in mortality per year (p = 0.0001). Postoperative length of stay decreased from 9.2 to 5.9 days. Related to this decrease in length of stay, hospital costs importantly decreased from $22,700 to $16,000 per case. Adjusting for increased patient severity, hospital costs decreased by $1,118 per year during this 9-year period [11].
| PCI Versus CABG Data From Registries of Entire Populations |
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| Randomized Controlled Trials of PCI With Stents Versus CABG in Multivessel Disease |
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The ARTS trial randomly assigned 1,205 patients with MVD in 67 centers [13]. The ARTS was a very PCI-friendly trial with enrollment only when the cardiologist and surgeon agreed that equivalent revascularization of two or more lesions could be achieved with either method. Only 5% of screened patients were enrolled. Patients enrolled were very low risk patients: no previous intervention, no congestive heart failure, no recent myocardial infarction, no cerebrovascular accident, mean age 61 years, and mean ejection fraction 0.61.
A major concern in the ARTS trial is a problematic difference between the PCI group and the CABG group in timely therapy after randomization. Treatment with with stents occurred an average of 11 days after randomization with no deaths, 1 myocardial infarction, and no strokes in this interval. Treatment with CABG averaged 27 days after randomization with 3 deaths, 4 myocardial infarctions, and 1 stroke in this interval. Delay in initiation of therapy in the surgical group led to a 0.5% mortality and more than 1% major adverse cardiac and cerebral event rate before therapy was initiated [16]. The authors' analysis of results included these pretreatment events despite this problematic difference between the groups. The following paragraphs present a postprocedure outcomes analysis, which accommodates the difference in timeliness of therapy in the two groups.
One-year results in ARTS were not surprising, with equivalent mortality and major adverse cardiac and cerebral event rate in each group. But despite PCI-friendly enrollment, deaths after the procedure were the same (15 in stent group, 14 in CABG group) at 1 year. As in EAST and BARI, percutaneous intervention for MVD does not have a lower early (1-year) mortality rate compared with CABG. This equal 1-year mortality is not the general perception of the public or of cardiologists. Additionally, 16.8% of the stent group versus only 3.5% of the CABG group required repeat revascularization by 1 year. Even with repeat revascularization, significantly more of the stent group had angina (21%) compared with the CABG group (10%) [16].
Five-year follow-up of the ARTS trial revealed postprocedure mortality of 7.1% at 5 years in the CABG group and 8% in the stent group (yielding a rough relative risk of 1.13). Five-year postprocedure death, myocardial infarction, or stroke rate was 13.5 % for CABG and 18% for PCI/stents (relative risk approximately 1.33). Repeat revascularization was 8.8% for CABG and 30% for PCI/stents (relative risk approximately 3.46). Despite the fact that the study was not powered to detect a mortality, myocardial infarction, or stroke difference between groups and the postprocedure data favored CABG, the authors of the 5-year follow-up concluded: "At five years there was no difference in mortality between stenting and surgery for MVD. Furthermore, the incidence of stroke or myocardial infarction was not significantly different between the two groups." They further endorse stenting by stating that "the difference in outcomes seen between bare metal stents (BMS) versus CABG is likely to narrow substantially with the advent of drug-eluting stents (DES)" [13].
The not-so-subtle bias of the ARTS authors favoring stenting is a particular concern because of at least one major conflict of interest that was not disclosed in the 1-year and 3-year reports. Doctor Brian Firth was on the board of governors of the study group and was acknowledged "for ... careful review of the manuscript and for ... constructive suggestions" [16]. Undisclosed was the fact that Dr Firth was Vice President of Cordis, a division of Johnson and Johnson, the stent manufacturer that supported the study [17]. In the report of 5-year results, Dr Firth was a coauthor of the report, and it was disclosed that he was "an employee of Cordis" [13]. The extent of this conflict is beyond the usual standards for properly run RCTs.
The ERACI II trial randomly assigned 450 MVD patients over 2 years in seven Argentine centers. The mean age of patients was 61 to 62 years; 40% of the patients had two-vessel disease. The 30-day mortality was 5.6% in the CABG group and 0.9% in the stent group. The remarkably high CABG mortality was attributed to unstable angina in 91% of the CABG patients. As in the ARTS trial, there was a relative delay in therapy for CABG patients after randomization (13.2 days for CABG and 4.2 days for stent). One death occurred in the CABG group before the procedure and no deaths in the stent group. The high 30-day mortality for CABG led to a significantly better 5-year mortality with stenting: 7.2% versus 11.6%. Five-year major adverse cardiac and cerebral event rate was better with CABG: 23.6% versus 34.7% (related to more revascularization in the stent group) [14, 18].
The major issue related to the outcomes in ERACI II is concern about the high 30-day CABG mortality. The yearly average CABG volume in the seven participating centers was 57 patients! Internal mammary artery use was 89% in these approximately 62-year-old patients. With an institutional CABG volume of 1 patient per week, a delay of 13 days for CABG (these would have to be called elective patients, despite the fact that they may have been "unstable" at the time of enrollment), internal mammary artery use in less than 90%, and a CABG operative mortality of 5.6%, a very serious question must be raised about the quality of surgical therapy in this study. The authors expressed concern about the unusually large percent of patients with unstable angina, stating that "results could change if the patient population treated had different baseline clinical characteristics or if technical proficiency for either treatment was altered" [14, 18].
The SoS trial from 53 centers in Europe and Canada randomly assigned 988 patients for whom revascularization was indicated and "appropriate by either strategy." The study sample size was calculated to detect a difference in revascularization in the two treatment strategies, assuming a repeat revascularization rate of 5% in the CABG group and 10% in the PCI group. At 2 years' median follow-up, revascularization was dramatically higher than assumed in the PCI group at 21%, compared with 6% in the CABG group (a 15% absolute difference rather than the 5% difference assumed when the study was designed, hazard ratio 3.85, p < 0.0001). Again there was a delay between randomization and therapy (mean 14 days for PCI and 23 days for CABG), but the CABG group was not disadvantaged by this delay (1 pretreatment death occurred, in the PCI group). The authors struggled with the fact that the CABG group had a significantly lower cumulative risk of death than the PCI group. At 2 years' median follow-up, mortality was 2% CABG versus 5% PCI (8 deaths versus 22 deaths, hazard ratio 2.91, p = 0.01). There was a higher rate of noncardiovascular death in the PCI group (9 versus 3, ratio 3:1), but even with the noncardiovascular deaths excluded, there were 13 deaths in the PCI group compared with 5 deaths in the CABG group (ratio 2.6:1). The authors acknowledged that "surgical mortality in SoS was low. To some extent this result is an indication of the nature of the trial population, who had a favorable coronary anatomy and surgical risk profile." They further state: "Our findings are most applicable to patients matching our trial population, many of whom would currently be offered a PCI procedure" [15].
The outcome of SoS clearly favored CABG as a superior treatment for MVD. But despite a difference in repeat revascularization rate for stenting that was three times the assumed difference (p < 0.0001) and a mortality in the PCI group that was 2.9 times the mortality in the CABG group (p < 0.01), the authors made the following interpretation as the entire conclusion of the Summary: "The use of coronary stents has reduced the need for repeat revascularization compared with previous studies that used balloon angioplasty, though the rate remains significantly higher than in patients managed with CABG. The apparent reduction in mortality with CABG requires further investigation" [15]. It is certainly notable that the conclusion of the summary failed to state the superior results observed with CABG versus PCI, and, instead, the conclusion provides yet another endorsement of PCI.
In the SoS authors' discussion of the low surgical mortality in SoS, they state: "Further information is required before any definitive conclusion can be drawn. Such information might become available with extended follow-up and a meta-analysis of the current stent versus surgery trials is planned." The SoS trial was "supported by funding from a consortium of stent manufacturers: Bard (now Medtronic), Guidant, and Schneider (now Boston Scientific)." There is no robust follow-up in progress for SoS; funding from these sources stopped after the 2-year report. There will be a mortality follow-up funded by a grant from the British Heart Foundation (personal communication from Dr R. H. Stables, Cardiothoracic Center, Liverpool, England). There will be no 5-year comprehensive report as there was for ARTS and ERACI II. Any meta-analysis will not include robust follow-up of SoS patients. In a way, a change in funding sources has led to a relative censoring of data that appeared to be not favorable to PCI.
| Drug-Eluting Stents |
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| British Assessment of Drug-Eluting Stents |
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Modeling was then done for MVD with higher risk patients (eg, poor left ventricular function, more than two vessels diseased, diabetic, and so forth). In patients with moderately increased risk compared with the low risk double-vessel disease patient, CABG became very cost effective compared with PCI with either bare metal stents or drug-eluting stents. The study concluded that "In the case of multiple-vessel disease the accumulated trial evidence comparing CABG with PTCA with bare metal stents is sufficient to project over 5 years an important and substantial survival advantage for CABG over PTCA with bare metal stents. Given that CABG is the standard therapy for most patients with multiple-vessel disease, it is difficult to justify substitution by a less effective treatment simply on the grounds that it is cheaper. ... This argument remains valid also in the case of DES, since the the apparent additional benefits from fewer interventions and consequent QoL (Quality of Life) gains are balanced by the extra costs of the new stents. Hence we find no grounds for the substitution of CABG by DES in multiple vessel disease. Indeed we find that higher risk individuals gain greater relative benefit from CABG, not less" [21].
The British conclusion was supported by a study from Stanford by Yock and colleagues [22], which used modeling to compare life-time cost effectiveness of PCI and CABG by updating and extending the results of BARI, updating the results for the effect of stents on PCI results. The model predicted a life-time survival benefit of CABG over PCI with stenting of 0.83 years. Initial CABG was a dominant therapy compared with initial stenting, with a lower life-time cost ($8,400) and a higher effectiveness (+0.31 QALY) compared with initial stenting. To accommodate the possibility that progressive improvements in drug-eluting stents may minimize restenosis, a sensitivity analysis was done to examine the effect of complete elimination of restenosis after stenting in the model. Even with complete elimination of restenosis, CABG remained a dominant therapy compared with PCI with stenting. The lifetime cost benefit was still less ($150), and a clinical benefit remained: + 0.27 QALY. The authors concluded: "... although elimination of target lesion restenosis does improve the short-term outcomes of catheter-based interventions. ... these improvements are not enough to make primary stenting less costly and more effective than CABG for relieving angina in patients with multivessel disease" [22].
| Stents Versus CABG in Clinical Practice |
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Results of 3-year follow-up revealed that repeat revascularization rate was reduced compared with the PCI without stent data presented in 2000, but not nearly so much as one would expect. Repeat revascularization rate was reduced from 37% to 35.1% after PCI between the two studies. Repeat revascularization rate after CABG increased from 3.3% to 4.9%. The relative risk of repeat revascularization after PCI compared with CABG was reduced from 11 times to 7 times higher [12, 23]. This result is consistent with and supports the concept presented earlier that a decrease in restenosis rate does not translate into an equivalent decrease in repeat revascularization rate . As in the SoS trial, the repeat revascularization rate after PCI with stenting was reduced, but not nearly so much as interventionalists would predict.
Mortality outcomes in the New York Registry report were most enlightening. For patients with two-vessel disease including the proximal left anterior descending artery (LAD), 3-year adjusted mortality was 7.9% with CABG versus 10.2% with stents; relative 3-year mortality with stents was 29% higher than with CABG. For patients with triple-vessel disease including the proximal LAD, the 3-year adjusted mortality was 10.7% with CABG versus 15.6% with stents. Relative mortality with initial stent therapy was 46% higher than with initial CABG. Mortality data for all categories of patients with MVD are presented in Figures 6 and 7
[23]. (Data for patients with MVD and nonproximal LAD disease obtained from Dr Michael J. Racz, University at Albany, State University of New York.)
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As restenosis is minimally related to mortality and since multiple trials have shown no survival benefit of DES compared with bare metal stents, there is every reason to believe the remainder of the British Health Service conclusion, that this substantial survival advantage for CABG is "valid also in the case of DES" [21].
| Observations on Appropriate Patient Education |
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In 2006, the statement of interventional cardiologists is: "The drug eluting stents have solved the problem that we used to have with restenosis. You read about it in the newspaper and you saw it on TV. Let us fix your blockages with the stents. There is no difference in mortality and we can always go back and do a coronary bypass procedure if we have to. I just don't want you to have your chest cracked." Note that Dr Guyton is no longer the perpetrator of the chest cracking. That is because Dr Guyton no longer has an opportunity to speak to the patient. But there is another big difference in 2006: we do have data on CABG versus PCI. If the mortality of initial stenting were the same as the mortality of initial CABG, we would all choose stenting (including this author). But the mortality of initial CABG versus initial stenting for MVD is emphatically not the same! Surgeons cannot continue to capitulate to the intuitive and emotional arguments of interventional cardiologists. We surgeons must present our argument with the same conviction that cardiologists present their argument. For the patient with triple-vessel disease including the proximal LAD, the patient should hear our message: "Coronary bypass is the procedure that gives you the best chance of being free from angina, and, if you have stenting as your first procedure instead of CABG, you have, on average, a 46% higher chance of dying in 3 years compared with CABG as your first procedure" (or a 24%, 28%, or 29% higher chance of dying for lesser MVD [Fig 7]).
In discussing coronary revascularization with a MVD patient, it is neither appropriate patient education nor good medical practice for the interventionalist to present only one argument. But do the interventionalists present both arguments? Can the interventionalist present both arguments? Is the interventionalist really going to say to the patient, "If you choose PCI for initial therapy compared with initial CABG, you will have a significantly higher 3-year risk of death"? For years, surgeons have been reluctant to dispute the arguments of local interventional cardiologists. This reluctance is understandable, as these cardiologists are the source of many CABG referrals, referrals that can be sent elsewhere if the surgeon is confrontational. But the application of PCI and CABG to MVD in the real world in a setting of good PCI and good surgeons in New York State, has resulted in a significantly higher 3-year mortality for initial PCI compared with initial CABG for all categories of MVD. There has been no improvement in this excess relative mortality in the stent era compared with the prestent era. Data presented above make a strong argument that drug-eluting stents will have little impact on mortality. It is the responsibility of surgeons to participate aggressively in the decision of revascularization modality for patients with MVD. We must educate primary care physicians, physician extenders, noninvasive cardiologists, invasive cardiologists, and patients. For surgeons to continue to accept passively whichever patients arrive at the operating room door in the hope of preserving personal referrals is a serious disservice to the patients whom we seek to serve.
| Acknowledgments |
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| Footnotes |
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| References |
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