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J Am Coll Cardiol, 1999; 34:1750-1759 © 1999 by the American College of Cardiology Foundation |
* Department of Cardiology, The Cleveland Clinic Foundation, Cleveland, Ohio, USA
Department of Cardiology, Hygeia Hospital, Athens, Greece
Department of Cardiology, Duke University Medical Center, Durham, North Carolina, USA
Montreal Heart Institute, Montreal, Canada
¶ Division of Cardiology, St. Louis University Health Sciences Center, St. Louis, Missouri, USA
# Department of Epidemiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
** Cardiology Division, Seattle V.A. Hospital, Seattle, Washington, USA
Division of Cardiology, Stanford University Medical Center, Stanford, California, USA
Manuscript received May 21, 1998; revised manuscript received March 29, 1999, accepted August 5, 1998.
Reprint requests and correspondence: Patrick L. Whitlow, Department of Cardiology, F25, The Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, Ohio 44195
whitlop{at}ccf.org
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Abstract |
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To determine the relative degree of revascularization obtained with bypass surgery versus angioplasty in a randomized trial of patients with multivessel disease requiring revascularization (Bypass Angioplasty Revascularization Investigation [BARI]), one-year catheterization was performed in 15% of patients.
BACKGROUND
Complete revascularization has been correlated with improved outcome after coronary artery bypass grafting (CABG) but not with percutaneous transluminal coronary angioplasty (PTCA). Relative degrees of revascularization after PTCA and surgery have not been previously compared and correlated with symptoms.
METHODS
Consecutive patients at four BARI centers consented to recatheterization one year after revascularization. Myocardial jeopardy index (MJI), the percentage of myocardium jeopardized by 
50% stenoses, was compared and correlated with angina status.
RESULTS
Angiography was completed in 270 of 362 consecutive patients (75%) after initial CABG (n = 135) or PTCA (n = 135). Coronary artery bypass grafting patients had 3 ± 0.9 distal anastomoses and PTCA patients had 2.4 ± 1.1 lesions attempted at initial revascularization. At one year, 20.5% of CABG patients had 1 totally occluded graft and 86.9% of vein graft, and 91.6% of internal mammary artery distal anastomotic sites had <50% stenosis. One year jeopardy index in surgery patients was 14.1 ± 11%, 46.6 ± 20.3% improved from baseline. Initial PTCA was successful in 86.9% of lesions and repeat revascularization was performed in 48.4% of PTCA patients by one year. Myocardial jeopardy index one year after PTCA was 25.5 ± 22.8%, an improvement of 33.8 ± 26.1% (p < 0.01 for greater improvement with CABG than PTCA). At one year, 29.6% of PTCA patients had angina versus 11.9% of surgery patients, p = 0.004. One-year myocardial jeopardy was predictive of angina (odds ratio 1.28 for the presence of angina per every 10% increment in myocardial jeopardy, p = 0.002). Randomization to PTCA rather than CABG also predicted angina (odds ratio 2.19, p = 0.03).
CONCLUSIONS
In this one-year angiographic substudy of BARI, CABG provided more complete revascularization than PTCA, and CABG likewise improved angina to a greater extent than PTCA.
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Over the last 20 years, angioplasty has also become a treatment alternative for patients with multivessel disease (10–18). The relative merits of bypass surgery versus angioplasty for treatment of patients with multivessel disease and angina or severe ischemia on exercise testing were tested in the Bypass Angioplasty Revascularization Investigation (BARI). Death and freedom from myocardial infarction (MI) were not statistically different in the 1,829 patients randomly assigned to surgery versus angioplasty at five-year follow-up (19). However, bypass surgery patients had improved symptom relief compared with those with angioplasty at one-year follow-up (20,21). A subset of consecu tively randomized patients at four centers in the BARI trial agreed to protocol catheterization at the end of one year to determine the degree of revascularization accomplished by the two treatment options and the relationship of the extent of jeopardized myocardium to clinical outcome. This article reports the results of the one-year angiographic substudy of the BARI randomized population.
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Methods |
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One year substudy. A consecutive group of 362 patients randomized in BARI at four investigative centers (Table 1) signed informed consent including one-year angiographic follow-up. One-year angiography was defined as either protocol mandated or an intercurrent angiogram occurring within a window of nine to 15 months following the baseline arteriogram. The angiographic analysis was based on the anatomy at one year angiography prior to any subsequent intervention.
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A myocardial jeopardy percentage was quantitated for each patient, with "myocardial jeopardy index (MJI)" defined as the sum of the estimated percentage of LV myocardium distal to 50% stenoses. By using a graphic database, each patient’s coronary distribution to LV myocardium was characterized, and total LV units were computed. Coronary lesions were positioned appropriately in relation to vessel branches and bifurcations in each patient. The total LV myocardial units jeopardized by lesions 50% were summed. The units of LV myocardium jeopardized by 50% lesions divided by the total LV territory units defined the extent of myocardial jeopardy. Wall motion and previous MI were not considered in the calculation of myocardial jeopardy (Appendix 1) (28,29).
Restenosis in patients who underwent percutaneous transluminal coronary angioplasty (PTCA) was defined as a 50% lesion attempted at the initial PTCA having 50% stenosis on an intercurrent angiogram or the one-year protocol angiogram. Graft lesions were referenced against the adjacent normal-appearing graft conduit, not the native coronary reference vessel. In determining the frequency of target vessel revascularization (TVR), PTCA patients who underwent intercurrent coronary artery bypass grafting (CABG) were assumed to have TVR on all vessel(s) treated at the initial PTCA.
Statistical analysis. Student t test and chi-square tests were used to compare baseline and follow-up characteristics. Logistic regression analysis was used to determine the odds of one-year angina by treatment assignment and myocardial jeopardy score (in units of 10 percentage points). Adjustment was made for history of smoking and angina at study entry which were significant predictors of one-year angina status. All analyses were conducted by the "intention to treat" assignment, with the exception of the exclusion from analysis of bypass surgery or angioplasty lesion outcome in four patients who did not receive their assigned treatment.
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Results |
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The number of patients randomized, eligible and studied at each participating institution is listed in Table 1. The baseline characteristics and one-year incidence of repeat revascularization and Q-wave MI of the angiographic substudy patients, the consecutive patients in BARI at the four participating institutions who were alive but not restudied and the remaining surviving BARI randomized cohort are compared in Table 2. Patients at participating centers without one-year angiography were significantly older than those undergoing one-year angiography and showed a trend for more congestive heart failure and diabetes. In fact, the subgroup without one-year angiography had a higher five-year all-cause mortality (16.1%) than those undergoing one-year angiography (5.1%, p = 0.007). Cardiac mortality was also higher in those not restudied (8.3%) than in those undergoing one-year recatheterization at the angiographic substudy sites (2.1%, p = 0.03). Baseline LV wall motion and myocardial jeopardy were similar in all groups. A higher percentage of patients at the one-year angiographic sites underwent repeat PTCA (14%) than at other BARI sites by one year (10%, p = 0.05). Fewer patients undergoing one-year angiography had Q-wave MIs during the first year (3.3%) than those at other BARI sites (6.9%, p = 0.05).
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Baseline characteristics of the 270 patients in the series completing one-year angiography are listed in Table 3 according to treatment assignment. Bypass and PTCA patients were similar in all baseline clinical and angiographic characteristics except that patients in the PTCA group were more likely to have had a prior history of congestive heart failure (9.6% vs. 3.0%, p = 0.04).
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50% per patient at study entry. Mean myocardial jeopardy at baseline was 60.8 ± 17.3% (Table 3), and the cumulative percentage of patients with any specified degree of myocardial jeopardy or less (cumulative frequency distribution of myocardial jeopardy) is displayed in Figure 1. Initial bypass surgery consisted of 3.0 distal anastomoses per patient. Ninety percent of patients received at least one internal mammary artery graft. Figure 2A is a flow diagram showing the initial procedure and one-year angiographic outcome of these patients, grafts and distal anastomotic sites. At one year, 20.5% of CABG patients had 1 totally occluded graft. However, 86.9% of vein graft and 91.6% of internal mammary artery distal anastomotic sites were patent without significant stenosis.
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Baseline ejection fraction, available in 96 of 135 surgery patients (71.1%), was 0.58 ± 0.10. Paired left ventriculography was quantitated in 68 restudied surgery patients, and one-year ejection fraction was 0.62 ± 0.13. Paired wall motion assessment was available in 131 patients with one-year wall motion score of 6.4 ± 2.4 and a baseline wall motion score of 7.0 ± 2.5.
One hundred nineteen of 135 (88.1%) surgery patients were angina free at the time of one-year follow-up (Fig. 3). Eleven patients had functional class I or II angina, while 5 patients had functional class III or IV angina.
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50% per patient at study entry, and myocardial jeopardy at baseline was 59.4 ± 16.0% (Table 3). Angioplasty patients had 2.4 ± 1.1 lesions per patient attempted at single or staged procedures.
One hundred twenty-four of 134 angioplasty patients (92.5%) had at least one significant lesion successfully dilated (
50% residual stenosis by caliper measurement with Thrombolysis In Myocardial Infarction [TIMI] 3 flow by core laboratory analysis). Of all attempted significant lesions, 284 of 327 were successfully dilated (86.9%). Of the successfully dilated lesions, 79 of 284 (27.8%) had 50% stenosis at one-year follow-up. Details of angiographic outcome of PTCA patients are delineated in Figure 2B. Target vessel revascularization by the time of one-year angiography was performed in 60 of 124 patients (48.4%) with at least one initially successfully dilated lesion.
In addition to the initial angioplasty targets, 1 ± 1.2 lesions per patient 50% had been untreated at the initial angiogram. This corresponded to 72 of 134 patients (53.7%) having at least one lesion 50% untreated at the initial PTCA. Twenty-five patients (18.6%) had undergone crossover to CABG by one year, including three patients with both repeat PTCA and subsequent CABG. Myocardial jeopardy at one year was 25.5 ± 22.8%, significantly improved from baseline (p = 0.001) but also significantly higher than in bypass surgery patients (p = 0.01) (Fig. 1). Improvement in myocardial jeopardy from baseline was 33.8 ± 26.1 percentage units, and 24.6% of PTCA patients had a myocardial jeopardy of 0.
Baseline LV ejection fraction, available in 104 of 135 patients (77%), was 0.59 ± 0.12. Paired one-year left ventriculograms were available in 84 patients (62.2%), and one-year LV ejection fraction was 0.61 ± 0.12. Paired wall motion assessment was available in 125 angioplasty patients with one-year wall motion score of 7.1 ± 3.1 and baseline wall motion score of 7.7 ± 3.1.
Ninety-five of 135 angioplasty patients were angina free at the time of one-year angiography (70.4%) (Fig. 3). Twenty-eight patients had functional class I–II angina, 9 patients had functional class III–IV angina and 3 patients had unstable angina. Percutaneous transluminal coronary angioplasty patients had significantly more angina than bypass patients at one year (p = 0.004).
Relation of angina and clinical events to MJI.
In order to analyze a potential independent treatment effect on the occurrence of angina beyond the effect of extent of jeopardized myocardium, patients were divided into three subgroups of myocardial jeopardy at one-year angiography: <10%, 10% to 33% and >33% (Fig. 4). Within each subgroup of myocardial jeopardy, PTCA patients reported more angina than CABG patients, most striking in the subgroup with >33% myocardial jeopardy (11% angina for CABG patients vs. 49% for PTCA patients, p = 0.004). Patients having CABG did have more Q-wave MIs than those with PTCA, 5.8% versus 1.9% in the subgroup with 10% to 33% MJI and 10.5% versus 0% in the 33% MJI subgroup, p = 0.03. More MIs in the CABG group likely contribute to but do not fully explain the lower prevalence of angina in CABG patients.
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Other clinical events occurring over four subsequent years of follow-up analyzed for the three subgroups of patients with specified degrees of one-year MJI are delineated in Table 4. Cardiac death was infrequent but did increase with each increment of myocardial jeopardy. Increasing MJI was highly significantly associated with the need for subsequent bypass surgery (p = 0.008). There was a nonsignificant trend suggesting higher risk of a major cardiac event in follow-up with increasing degrees of MJI at one year (p = 0.12).
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Discussion |
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Completeness of revascularization. Completeness of revascularization has long been argued to be predictive of follow-up events in bypass surgery patients (30–33). However, the extent of revascularization has not been unequivocably proven to be predictive of outcome in angioplasty patients (34–43). Therefore, BARI was designed to treat patients with multivessel disease and significant ischemia without requiring that the proposed PTCA procedure(s) provides revascularization anatomically equivalent to that provided by surgery. Indeed, study results confirm that surgery provided more complete revascularization than PTCA by initial strategy and also at one year.
Completeness of revascularization at one year with PTCA is affected by initial strategy of lesions attempted, by success or failure of the PTCA, by restenosis of a subgroup of initially successfully dilated lesions and by progression of native coronary disease. Of the 60 angioplasties performed following the initial revascularization procedure in patients randomized to PTCA, 51 (85.0%) included an attempt of a lesion previously dilated at the index procedure (restenosis), 24 (40.0%) included an attempt of a lesion not previously dilated at the index procedure (new lesion) and 15 (25.0%) included an attempt of both a restenotic lesion and a new lesion. Target vessel repeat revascularization was performed in 40.0% of 50 PTCA patients with initially complete revascularization versus 45.9% of 74 patients with initially incomplete revascularization (p = 0.58). Thus, intent of the angioplasty operator to provide complete versus incomplete revascularization did not appear to influence the high incidence of subsequent repeat revascularization procedures in this angiographic substudy.
Less complete revascularization with PTCA was not associated with worsened ejection fraction or LV wall motion at one-year follow-up compared with surgery. With both treatments, patients had equal wall motion score and ejection fraction at one year. However, higher degrees of myocardial jeopardy at one year were associated with an increased frequency of subsequent bypass surgery.
Angina status. The previously reported improved angina status of bypass surgery patients over PTCA randomized patients at one year (20,21) was confirmed in this angiographic substudy. Myocardial jeopardy index was more predictive of angina in PTCA patients than in CABG patients. The degree of anatomical revascularization and resultant MJI differences between the two treatment options is certainly part of the explanation for the greater relief of angina with surgery. However, these data suggest that there are additional factors involved in angina beyond the anatomical degree of revascularization, as surgery provided greater relief of angina than PTCA even with a similar degree of myocardial jeopardy. The reason for this finding is likely multifactorial, including both psychological factors such as the relief of cognitive dissonance and physiologic factors such as change of pain perception associated with an operative procedure or a perioperative MI. In addition, angiography is not a perfect method of assessing the angina-provoking potential of coronary disease. No attempt was made in this analysis to account for stenoses >50% subserving "infarcted myocardium" because of the inadequacy of angiography in classifying myocardial viability. This limitation and the small sample size analyzed may have affected the low incidence of angina found in bypass surgery patients with >33% MJI, who had 10.5% Q-wave MI incidence by one year compared with 0 for PTCA patients in the same jeopardy category, p = 0.03. This study was not designed to determine the mechanisms involved in angina perception, and, therefore, we can only speculate about and document this interesting phenomenon.
This angiographic substudy reports patient status at one particular time point, and most patients with severe angina at one-year angiography were treated with further revascularization. In the complete BARI cohort, angina status differences between PTCA and surgical patients were attenuated by three years with both groups experiencing similar angina relief at five years (20,21). It is therefore reasonable to expect that this will be the case for the BARI subgroup that was angiographically studied with the angioplasty patients requiring a greater number of revascularization procedures.
Internal mammary artery versus saphenous vein bypass graft patency. The one-year patency of 98% for internal mammary artery grafts in this study of 135 consecutive patients establishes a benchmark for current bypass surgery. The one-year patency of saphenous vein grafts performed by the same group of surgeons was 87%, similar to previous data reported in the early and mid 1980s (44,45). These data are consistent with the current trend in clinical care to utilize mammary artery grafts in virtually all patients undergoing elective bypass surgery.
Study limitations. The angiographic substudy included only 15% of the BARI randomized cohort, and therefore extrapolating conclusions based on this subgroup to the entire group is based on the relative similarity of baseline characteristics and five-year clinical course between the angiographically restudied subgroup and the other randomized BARI patients. The finding of more angina at one year with PTCA in the angiography cohort was also similar to that reported in the main BARI trial (20). Similar concurrence was observed in the subgroup analysis of economics and quality of life (21). While it would have been desirable to have a larger substudy, the authors feel that the results of this study of consecutive patients are both interesting and representative.
Angiography clearly has limitations in the assessment of the severity of coronary disease, and alternative methods (intravascular ultrasound, flow reserve, or fractional flow reserve measurement or even routine stress testing) would have been helpful to compare to these angiographic analyses. However, these data were not collected in BARI, and therefore are not available for comparison.
Conclusions. In this cohort of protocol-driven angiographically restudied patients in the BARI trial at one year, those having initial PTCA were more likely to report angina than those having CABG. Reduction in myocardial jeopardy for PTCA patients was also less than for CABG patients despite more repeat revascularization procedures in the angioplasty group. Increased MJI was related to increased frequency of angina at one year, and to an increased need for CABG in the four subsequent years of follow-up. At one year after revascularization, every increase of 10 percentage units in myocardial jeopardy increased the probability of angina by 28%.
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Appendix |
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TopAbstractMethodsResultsDiscussionAppendixReferences |
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50% stenoses considered "jeopardized." Each major branch vessel (diagonals, circumflex marginals, ramus, posterior descending and posterolateral arteries) was assigned a territory unit of 1 (small), 2 (medium) or 3 (large), based on the vessel’s size and length. The distal terminating portions of the left anterior descending, right coronary artery and circumflex vessels were similarly sized. Three units of territory were assigned to the septal vessels. By using a graphic database, each patient’s coronary distribution to LV myocardium was characterized and total LV units computed. Coronary lesions were positioned appropriately in relation to vessel branches and bifurcations in each patient. The total LV myocardial units jeopardized by lesions 50% were summed. The ratio of the number of units of LV myocardium jeopardized by 50% lesions divided by the total LV territory units, expressed as a percentage, defined the extent of myocardial jeopardy.
Coronary angioplasty mitigated all of the jeopardy distal to lesions that were successfully dilated to a stenosis below 50%. Similarly, bypass grafts mitigated all jeopardy distal to the insertion site of the graft and retrograde, including branches, up to the point of a more proximal lesion that is 50% severity. Myocardial jeopardy expressed as a percent provides a semiquantitative, continuous variable measurement of the amount of LV myocardium that is subject to ischemia by 50% stenoses. The reproducibility of this measurement has been assessed in blinded recycling of 70 angiograms. The mean difference between readings was 3.2 units with a standard deviation of 11.8 jeopardy units. The intraclass correlation of readings was 0.77.
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Footnotes |
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