Ann Thorac Surg 2005;80:1340-1346
© 2005 The Society of Thoracic Surgeons
Original article: Cardiovascular
Percutaneous Intervention Versus Coronary Bypass Surgery for Patients Older Than 70 Years of Age With High-Risk Unstable Angina
Kodangudi B. Ramanathan, MD, FACC
a
,
Darryl S. Weiman, MD, JD
a
,
*
,
Jerome Sacks, PhD
b
,
Douglass A. Morrison, MD, FACC
c
,
Steven Sedlis, MD, FACC
d
,
Gulshan Sethi, MD, FACC
e
,
William G. Henderson, PhD
b
a Veterans Administration Medical Center, Memphis, Tennessee
b Veterans Administration Medical Center, Hines, Illinois
c Veterans Administration Medical Center, Denver, Colorado
d Veterans Administration Medical Center, New York, New York
e Veterans Administration Medical Center, Tucson, Arizona
Accepted for publication March 16, 2005.
* Address reprint requests to Dr Weiman, 956 Ct, Suite G212, Memphis, TN 38163 (Email: dweiman{at}utmem.edu).
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Abstract
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BACKGROUND: The Angina With Extremely Serious Operative Mortality Evaluation (AWESOME) study was a multicenter Veterans Affairs randomized trial and registry that compared long-term survival of percutaneous coronary intervention with coronary artery bypass graft surgery for the treatment of patients with medically refractory myocardial ischemia and at least one additional risk factor for an adverse outcome with bypass. Both the randomized trial and the registry demonstrated comparable 3-year survival. The purpose of this study was to compare bypass and percutaneous intervention survival of AWESOME patients who were older than 70 years of age.
METHODS: Over a 5-year period (1995 to 2000), 2,431 patients with medically refractory myocardial ischemia and at least one of the following five risk factors (prior heart surgery, myocardial infarction within 7 days, left ventricular ejection fraction less than 35%, age > 70 years, intraaortic balloon pump requirement to stabilize) were identified. Of these patients, 1,278 were older than 70 years of age. Eight hundred, seventy-one patients were turned down by at least one physician, 407 were acceptable to both physician and surgeon for randomization, and 236 (60%) consented to randomization. Of the 1,042 eligible patients who were not randomized, 871 had their revascularization directed by a physician who was not involved in the study. One hundred, seventy-one patients who were acceptable for randomization by both the interventional cardiologist and the cardiac surgeon refused consent.
RESULTS: Bypass and percutaneous intervention survival were compared using Kaplan-Meier curves and log rank tests. Bypass and percutaneous intervention 36-month survival rates for patients older than 70 years of age were 76% and 75%, respectively, among the eligible patients. Survival was 71% and 78% among those patients who were randomized and 76% and 67% in the physician-directed subgroup. Of those patients who chose their revascularization techniques, the survivals were 79% and 85%, respectively. The survival differences are not large, and none of the global log rank tests of bypass compared with percutaneous intervention survival showed a statistically significant difference over 5 years.
CONCLUSIONS: Both the randomized and registry subgroups of patients who were older than 70 years of age support the trial conclusions that either bypass or percutaneous intervention effectively relieves medically refractory ischemia among high-risk unstable angina patients whose age was greater than 70 years.
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Introduction
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People who are 65 years of age or older represent the population segment with the greatest growth rate in the developed world [1]. Most randomized clinical trials in coronary artery disease have failed to pay attention to this subgroup of patients [2]. The problems associated with aging are not related to aging alone, but are associated with risk factors and co-morbidities. Unlike cigarette smoking, most of the risk factors for coronary disease, such as hypercholesterolemia, hypertension, and type II diabetes mellitus are age related and tend to be present in this older age group [3]. Furthermore, the risk factors in the aged have been present for a longer time than among young patients. Other co-morbidities, such as renal failure and the presence of atherosclerosis in other vessels, increase the complication rate associated with interventional treatment of coronary artery disease in these patients [4].
Randomized clinical trials comparing percutaneous coronary intervention (PCI) with coronary artery bypass graft (CABG) surgery have demonstrated comparable long-term survival [5–17]. In most trials, relief of angina has been comparable or slightly better with CABG surgery, and the need for further revascularization procedures has also favored the CABG subgroup. The AWESOME study targeted patients for inclusion that prior trials had consistently excluded because of their high-risk status. This article presents the results of CABG surgery and PCI revascularization of randomized and nonrandomized registry AWESOME patients whose age was greater than 70 years.
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Patients and Methods
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The AWESOME protocol, baseline characteristics of randomized patients, and 3-year outcomes of the randomized cohort have been previously reported [18–19]. Patients were enrolled at 16 Veterans Administration medical centers during a 5-year period from 1995 to 2000.
During the study's 5-year period, 2,431 patients with medically refractory myocardial ischemia and at least one of five risk factors (prior heart surgery, myocardial infarction within 7 days, left ventricular ejection fraction less than 0.35, age > 70 years, and intra-aortic balloon required to stabilize) were identified. After coronary arteriography, both the interventional cardiologist and the cardiac surgeon reviewed all potentially randomizable patients. The principal investigator for cardiac surgery determined suitability for cardiac surgery, and the principal investigator for interventional cardiology determined suitability for percutaneous intervention. By accepting to participate in the study, the surgical principal investigator could not deny a percutaneous intervention nor could the cardiology principal investigator deny coronary bypass surgery. One thousand, two hundred, seventy-eight of the 2,431 patients were older than 70 years of age. Four hundred, seven patients were acceptable to both the interventional cardiologist and the cardiac surgeon for randomization. Two hundred, thirty-six patients (60%) consented to randomization and one hundred, seventy-one refused randomization. The registry consisted of eight hundred, seventy-one eligible patients whose revascularization was physician-directed. The physician-directed group consisted of patients who were not found to be suitable for bypass surgery by the surgical principal investigator and those found unsuitable for percutaneous intervention by the interventional cardiologist. The patient-directed group consisted of 171 randomizable patients acceptable to both the interventional cardiologist and the cardiac surgeon, but refused consent to be randomized and chose the intervention they and their family preferred.
Statistical analysis showed differences in baseline variable frequencies that were tested by 
2 tests for proportions. Long-term survival was measured by Kaplan-Meier survival estimates that were plotted. The statistical significance of global differences between survival curves was tested by log-rank tests. Differences between 36-month CABG and PCI survival were computed along with z-tests of the differences.
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Results
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Baseline Features
A baseline comparison of randomized and registry patients whose age was greater than 70 was performed. The overall profile of these groups was similar except for prior CABG surgery, three-vessel disease, and thrombolysis in myocardial infarction (TIMI) no flow, which were more prevalent in the registry patients. Physician-directed and patient-choice baseline rates were also similar except for three-vessel disease and TIMI no flow, which were more prevalent in the physician-directed subgroup (Table 1).
Subgroups allocated to CABG surgery or PCI were also compared. Physician-directed patients assigned to CABG surgery had a substantially higher prevalence rate for diabetes and three-vessel disease, and a lower rate for prior CABG surgery, prior PCI, and TIMI no flow compared with those assigned to PCI. Patient-choice patients receiving CABG surgery had a higher prevalence rate of TIMI no flow compared with those receiving PCI. These factors were significantly associated with allocation to CABG surgery or PCI in the two registry subgroups (Table 2).
CABG and PCI Methods
Of the 614 patients that underwent surgical revascularization, 386 patients received a left internal mammary bypass graft to the left anterior descending coronary artery. Ten patients received a right internal mammary graft, and 10 others received both LIMA and right internal mammary artery grafts. In this subgroup, none received radial or other forms of arterial grafts. The majority of patients (258) received three bypass grafts. One hundred, forty-one patients received four bypass grafts, 120 received two bypass grafts, and 22 patients received only one graft. Similar to the overall AWESOME study and registry there was an increase in the use of stents and other forms of interventional treatment (such as rotablations) during the course of the study. However, directional atherectomy was not utilized in this study.
Short-Term Outcomes
Percutaneous coronary intervention revascularization rates were somewhat higher than those for CABG surgery. Coronary artery bypass graft surgery in-hospital mortality was higher, but the 30-day, 6-month, and 12-month CABG and PCI survival rates were all similar in the random and registry cohorts (Table 3).
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Table 3. Short-Term Coronary Artery Bypass Graft and Percutaneous Intervention Outcomes of Patients Older Than 70 Years of Age
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Long-Term Survival
In the physician-directed group, survival free from unstable angina was higher in the CABG patients as compared with the PCI patients. Similarly, survival free of unstable angina and repeat revascularization is higher among CABG patients for the total cohort as well as for the physician-directed group (Table 4).
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Table 4. Coronary Artery Bypass Graft and Percutaneous 36-Month Survival, Survival Free of Unstable Angina, and Survival Free of Unstable Angina or Repeat Revascularization of Patients Older Than 70 Years of Age
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Figures 1 through 4
present plots of Kaplan-Meier estimates for CABG and PCI survival for the randomized, physician-directed, and patient-choice cohorts, along with the global log-rank test for all eligible patients. The yearly CABG and PCI survival estimates appear at the bottom of each plot.
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Fig 1. Kaplan-Meier 5-year survival curves of coronary artery bypass graft (CABG) surgery and percutaneous intervention (PCI) for eligible patients older than 70 years of age. ( = CABG; X = PCI.)
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Fig 2. Kaplan-Meier 5-year survival curves of coronary artery bypass graft (CABG) surgery and percutaneous intervention (PCI) for randomized cohorts older than 70 years of age. ( = CABG; X = PCI.)
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Fig 3. Kaplan-Meier 5-year survival curves of coronary artery bypass graft (CABG) surgery and percutaneous intervention (PCI) for physician-directed cohorts older than 70 years of age. ( = CABG; X = PCI.)
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Fig 4. Kaplan-Meier 5-year survival curves of coronary artery bypass graft (CABG) surgery and percutaneous intervention (PCI) for patient-choice cohorts older than 70 years of age. ( = CABG; X = PCI.)
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Relationship of Risk Factors to CABG Allocation
The choice of revascularization is modified by the presence of additional specific risk factors among the physician-directed and patient-choice subgroups. For example, the CABG assignment rate for physician-directed patients drops from 63% overall to 29% for patients with a prior CABG. This decrease is statistically significant (2 less than 0.05) and appears to indicate a physician trend away from CABG revascularization for patients over the age of 70 with a prior CABG. Generally the presence of additional risk factors does not appear to be associated with the choice of revascularization in either registry cohort (Table 5).
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Table 5. Percentage Allocation to Coronary Artery Bypass Graft Between Physician-Directed and Patient-Choice Patients Older Than 70 Years of Age by Additional High-Risk Baseline Characteristics
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Comment
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The AWESOME Veterans Affairs Cooperative randomized study was specifically designed to compare PCI with CABG surgery for those patients who had unstable angina and other high-risk features [18]. Similar to a previously published study comparing the randomized and registry cohorts in the AWESOME study, the subgroup of patients who were older than 70 years of age demonstrated a similar profile between the two cohorts [20]. The differences noted were limited to those with previous bypass operations, significant three-vessel coronary artery disease, and total occlusion (TIMI no flow). Patients with previous bypass operations were more frequently directed to have a percutaneous intervention by their physicians. Within the registry, the choice for bypass operations among those older than 70 years of age with previous bypass surgery is significantly diminished for the registry patients as a whole and was especially diminished in the physician directed subgroup. Other high-risk features, such as prior angioplasty, recent myocardial infarction, diabetes, prior stroke, multivessel coronary artery disease, or total occlusion did not significantly change the percentage allocation to coronary artery bypass grafting. It is clear that there was a tendency to discourage redo operative intervention for those patients age 70 years and older.
Reluctance to randomize those with three-vessel coronary artery disease to percutaneous intervention seemed to be due to physician preference to recommend bypass surgery in this subgroup. This observation was also noted in the overall study comparing the random and registry patients [20]. In the total AWESOME study, there was also a bias toward bypass grafting for the subgroup of patients aged 70 and older that reflected a physician preference in the absence of trial-based guidelines [20]. Most previous studies have not randomized patients with total coronary occlusion (TIMI no flow) [5–10]. In the physician-directed group in the present study there was a preference for percutaneous intervention, whereas in the patient-directed group the preference was for bypass operation. This finding was consistent with a previous study comparing randomized and registry cohorts in the AWESOME trial [20].
This study did not demonstrate a significant difference in survival among patients randomized to percutaneous intervention or coronary artery bypass grafting in the subgroup of patients aged 70 years or older [5–10]. This finding was consistent for short-term, intermediate-term, and long-term survival.
Most trials dealing with either percutaneous intervention or bypass grafting among older patients (including octogenarians) have noted the increasing safety in the performance of either procedure with the acknowledgment of an escalation in morbidity and even mortality among the unstable patients in comparison with younger patients of either sex with stable angina [21–24]. Previous studies have also noted a greater prevalence of females among the aged [25–26]. Because the present study was based on the Veterans Administration it lacked the female component of other previous trials. Among the previous randomized trials, the Bypass Angioplasty Revascularization Investigation study noted that old age was one of the predictors of mortality for both percutaneous intervention and bypass grafting [27]. In the Bypass Angioplasty Revascularization Investigation trial, the 5-year mortality for patients older than 65 years randomized to coronary artery bypass grafting was less than that observed for those randomized to angioplasty. However, when the diabetics in this study were removed from analysis, this difference no longer persisted [28]. Unlike the Bypass Angioplasty Revascularization Investigation study, the AWESOME study did not find a significant survival difference between those randomized to angioplasty or bypass grafting among diabetics [29]. In a nonrandomized comparison of octogenarians, Kaul and colleagues [30] noted a better 5-year survival among patients treated with bypass grafting than angioplasty. This finding was similar to what we observed in the physician-directed registry group in which there was a 9% improvement in long-term survival for the surgical cohort. However, in a smaller group of patients who were 75 years of age or older, Japanese investigators found no difference in survival between those undergoing bypass grafting and angioplasty [31]. Similarly, a study by Bonnier and colleagues [32], found a similar actuarial survival of patients greater than 75 years old followed out to 10 years. Three more recently conducted trials comparing stenting with bypass grafting for multivessel coronary disease resulted in three different conclusions. The ERACI II trial found a greater mortality with bypass grafting compared with stenting at 1 year [14]. The Stent or Surgery (SOS) trial demonstrated a higher mortality among the stent group compared with bypass grafting, and the Arterial Revascularization Therapies Study trial found equal 1-year and 3-year survival among patients randomized to grafting or stenting [15, 33, 34]. The mean age of patients in these previous studies is 61 years, and it is unclear how the older subgroup of patients aged 70 or older compared between PCI and coronary grafting.
With regard to morbidity, the present study demonstrates superior survival free of unstable angina and repeat revascularization for those treated with bypass grafting when compared with percutaneous intervention. This finding was also observed in the AWESOME study as a whole and other randomized trials comparing these two modalities of treatment [5–10, 19]. This finding reflects the tendency for re-stenosis in the PCI group. Although the majority of patients in this study received a stent, the earlier hope that coronary stenting would obviate the need for reintervention has not occurred.
The major limitation of the present study is the lack of women. With studies such as the AWESOME study in which randomization is difficult, follow-up of nonrandomized patients (the AWESOME registries) can complement findings in the randomized groups.
In conclusion, long-term survival was not significantly different in the PCI and CABG groups for this group of elderly male veterans with unstable angina at high risk for coronary artery bypass grafting. The bias to choose either one of these modalities of therapy may be unwarranted unless defined by specific subsets in which one form of therapy is shown to be clearly superior to the other. There appears to be a considerable reluctance to offer bypass grafting to the group of elderly patients who have had a previous bypass operation. Whether newer modalities of surgical intervention, such as off-pump bypass, or better methods to deal with patients who have patent mammary grafts would change this pattern of practice remains to be seen.
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Notice From the American Board of Thoracic Surgery
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The 2005 Part I (written) examination will be held on Monday, December 5, 2005. It is planned that the examination will be given at multiple sites throughout the United States using an electronic format. The closing date for registration was August 1, 2005. Those wishing to be considered for examination must apply online at www.abts.org.
To be admissible to the Part II (oral) examination, a candidate must have successfully completed the Part I (written) examination.
A candidate applying for admission to the certifying examination must fulfill all the requirements of the Board in force at the time the application is received.
Please address all communications to the American Board of Thoracic Surgery, 6333 N St. Clair St, Suite 2320, Chicago, IL 60611; telephone: (312) 202-5900; fax: (312) 202-5960; e-mail: mailto:info{at}abts.org.
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Abstract
Introduction
