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(Circulation. 1996;93:1954-1962.)
© 1996 American Heart Association, Inc.

Articles

Effectiveness of Revascularization in the Emory Angioplasty Versus Surgery Trial

A Randomized Comparison of Coronary Angioplasty With Bypass Surgery

Xue-Qiao Zhao, MD; B. Greg Brown, MD, PhD; Douglas K. Stewart, MD; Lynn A. Hillger, PhD; Huiman X. Barnhart, PhD; Andrzej S. Kosinski, PhD; William S. Weintraub, MD; Spencer B. King, III, MD

From the Department of Medicine, Cardiology Division, University of Washington School of Medicine, Seattle, and Division of Interventional Cardiology, Emory University School of Medicine, Atlanta, Ga (H.X.B., A.S.K., W.S.W., S.B.K.).

Correspondence to Xue-Qiao Zhao, MD, Cardiology, Box 358771, 1914 North 34th St, Suite 105, University of Washington, Seattle, WA 98103.

	Abstract

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Background The Emory Angioplasty Versus Surgery Trial (EAST) was designed to determine whether percutaneous transluminal coronary angioplasty (PTCA) is as effective as coronary artery bypass graft surgery (CABG) in restoring arterial perfusion capacity in eligible patients with multivessel disease.

Methods and Results Of 392 patients in EAST, 198 were randomized to PTCA and 194 to CABG. Index lesions (2.7±1.0 per patient) were those with 50% stenosis judged treatable by both angioplasty and surgery. Coronary segments jeopardized by these index lesions were designated as index segments (4.4±1.4 per patient). Percent stenosis was measured by quantitative angiography at the point of greatest obstruction in the main perfusion path of each index segment. The EAST primary arteriographic end point was the percent of a patient's index segments with <50% stenosis in the main perfusion pathways at 1 and 3 years. At baseline, the percent of index segments for which revascularization was attempted was 85% for PTCA and 98% for CABG (P<.0001). At 1 year, PTCA patients had a smaller percentage of successfully revascularized index segments than CABG patients (59% versus 88%, P<.001). At 3 years, the findings were similar but less striking (70% versus 87%, P<.001). When only "high-priority" index segments (2.1±1.6 per patient) were considered, baseline attempts were comparable (96% versus 99%, P=NS); despite this, CABG remained more successful at 1 (64% versus 93%, P<.001) and 3 (76% versus 89%, P<.01) years. However, the mean percent of index segments free of severe stenosis (70%) did not differ between PTCA and CABG patients at 3 years (93% versus 95%, P=NS). Furthermore, the frequency of patients with all index segments free of severe stenosis did not differ between the two groups at 1 (76% versus 83%, P=NS) or 3 (82% for both PTCA and CABG) years.

Conclusions In patients with multivessel disease, index segment revascularization was more complete with CABG than PTCA at both 1 and 3 years. However, when the physiological priority of the target lesion and the measured severity of the residual stenosis are taken into account, the advantage of CABG becomes less significant or nonsignificant. This may, in part, explain why these two strategies did not differ in terms of the EAST primary clinical end points over 3 years.

Key Words: coronary disease • angioplasty • bypass • revascularization

	Introduction

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Two commonly used and clinically effective myocardial revascularization procedures are CABG and PTCA.^{1 2 3 4} Coronary angioplasty has been widely accepted as the initial revascularization procedure for treatment of most single-vessel coronary artery disease.^{4 5 6} CABG has been the standard form of revascularization for multivessel disease. However, in the last decade, PTCA has been proposed and evaluated in initial trials as an alternative to CABG in these patients,^{7 8 9 10 11 12 13 14 15 16 17} but definitive conclusions await more comprehensive studies.

EAST,¹⁸ conducted at Emory University, is among the first of these. This comparison of PTCA and CABG in terms of clinical outcomes (death, Q-wave myocardial infarction, or a large ischemic thallium defect) and the frequency of additional procedures has been reported elsewhere.¹⁹

In EAST, arteriograms were obtained routinely at baseline, at 1 and 3 years, and at the time of interval revascularization procedures for symptomatic ischemia. These arteriographic images were analyzed independently at the University of Washington in Seattle. The primary arteriographic end point was the proportion of a patient's initially jeopardized (50% stenosis) arterial segments with <50% stenosis in the main perfusion pathway as assessed by QCA. In this report, we compare two patient groups randomized to one of these two initial treatment strategies in terms of baseline arteriographic characteristics and the above revascularization end point at 1 and 3 years.

	Methods

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Patients
Patients were enrolled from those referred for revascularization to the Emory University cardiology and cardiac surgery divisions.^{18 19} Of 5118 patients evaluated, 842 were eligible, and 392 consented to participate. These had multivessel (two- or three-vessel) ischemic heart disease, no total coronary occlusions of >8 weeks' duration, and at least one lesion of 50% diameter stenosis in each of the two or three diseased vessel systems. The patients were judged suitable for treatment by either PTCA or CABG. Exclusion criteria included any previous CABG or PTCA, 30% left main coronary narrowing, target lesions longer than 20 mm, and left ventricular ejection fraction <25%. The procedures were performed by use of current techniques without the primary use of new devices. Patients were followed clinically by Emory investigators at protocol preprocedure and postprocedure time points and by their referring physicians at times of recurrent ischemia. Protocol follow-up coronary arteriography and stress-thallium imaging were performed at 1 and 3 years.

Definitions of Index Lesions, Index Segments, and Main Perfusion Pathways
Before randomization, the patient's baseline angiographic anatomy was evaluated by an Emory cardiologist and surgeon. The coronary anatomy, as seen in the baseline clinical arteriogram, was interpreted in terms of the percent diameter reduction measured by digital caliper in the standard CASS²⁰ representation of the coronary anatomy (see Fig 1A). Lesions with 50% stenosis that could be treated by both PTCA or CABG were called index lesions. Coronary segments jeopardized by these index lesions were designated as index segments. The index segments were specified before randomization by consensus of the surgeon and the invasive cardiologist. An index segment could be any 1 of the 12 segments commonly grafted to bypass proximal stenosis. An index lesion can jeopardize >1 of these segments. In the example of Fig 1A, the 70% LAD stenosis limits perfusion of the middle and distal LAD and the stenotic second diagonal branch. An angioplasty or bypass of that index lesion would favorably influence perfusion to both LAD vascular distributions. The main channel for blood flow to each of these index segments is called its main perfusion pathway. For index segments distal to an angioplasty-treated lesion, the main perfusion pathways are through the proximal native arteries. For a grafted index segment, the main perfusion pathway is through the graft unless the graft is more severely stenotic than the proximal lesion, in which case the main perfusion pathway would be through the diseased native artery.

View larger version (34K): [in this window] [in a new window]   Figure 1. A, A hypothetical baseline anatomy. Before randomization, in this RCA-dominant coronary system, the middle and distal LAD, second diagonal branch, and third marginal branch were index segments, given the disease severity of 40% stenosis (S) in middle LAD, 70% stenosis in distal LAD, 70% stenosis in the second diagonal branch, and 55% stenosis in midcircumflex. Each index segment had an identifiable perfusion pathway. In this case, it was from proximal to middle and distal LAD or to the second diagonal branch and from proximal through middle circumflex to the third marginal branch. The first and second marginal branches were not index segments if their proximal lesion was mild (as in the example). B, In this PTCA example, middle and distal LAD were successfully revascularized, but the second diagonal was not. The midcircumflex lesion was not dilated at baseline procedure. Therefore, 50% of this PTCA patient's index segments were revascularized at this time. C, CABG follow-up. In this CABG example, middle and distal LAD and the third marginal branch were successfully bypassed, but the second diagonal graft was occluded. This CABG patient had 75% successful revascularization.

Protocol and Nonprotocol Arteriograms
Those randomized to PTCA underwent the procedure within 2 weeks of the baseline film. Protocol angiography was scheduled at 1 year (±1-month window) and at 3 years (±3-month window) after the respective procedures. Out-of-window angiograms were not excluded from this analysis; nevertheless, 85% and 95% of the 1- and 3-year studies, respectively, fell within the target windows. At each catheterization, viewing angles, field size, catheter size, and vasoactive drug use were recorded, to be repeated during subsequent studies. However, no angiograms were excluded because of a mismatch of any variable. Index lesions were measured, as described below, from the baseline film and the two protocol follow-up films and immediately after the initial PTCA procedure. Figs 2 and 3 demonstrate CABG and PTCA arteriographic examples, respectively.

View larger version (138K): [in this window] [in a new window]   Figure 2. Arteriographic example from a bypass patient. This bypassed RCA stenosis was occluded at both 1 and 3 years. The RCA graft was patent at 1 year but was significantly narrowed at the 3-year protocol angiogram, when the patient underwent angioplasty. Even though this graft body stenosis was successfully dilated, the grafted RCA segments were not considered revascularized at 3 years. F/U indicates follow-up.

View larger version (111K): [in this window] [in a new window]   Figure 3. Arteriographic example from a PTCA patient. This RCA lesion became restenotic twice and was redilated. It was found totally occluded at 1 year. The patient underwent bypass surgery. At 3 years, the RCA was occluded, and the graft was patent. RCA segment revascularization in this PTCA patient was called unsuccessful at 1 year and successful at 3 years.

All films were stored securely at Emory University Hospital. The baseline and 1-year pair, plus any nonprotocol films in that interval, were mailed to the quantitative arteriography laboratory at the University of Washington in Seattle for side-by-side analysis. When the 3-year follow-up angiogram was completed, all films made on the patient were mailed to Seattle for review and analysis of the images obtained after year 1. Measurements were blinded to patient characteristics, clinical course, and actual randomization.

Strategy for Analysis
The goal of the analysis was to measure the most flow-limiting or worst stenosis in the principal or main perfusion pathway of each index segment. This concept can best be illustrated by examination of Fig 1. Before intervention (Fig 1A), the middle and distal LAD and the second diagonal and third marginal branches were index segments. The first and second obtuse marginal branches were not index segments because their worst proximal lesion was mild. If the patient were randomized to PTCA, the most severe lesions in the LAD, second diagonal, and third marginal perfusion pathways would be measured in the baseline film, immediately after angioplasty, and on protocol at 1 and 3 years (see Fig 1B). The location of the most severe narrowing may change with time. In Fig 1B, after a successful angioplasty of the 70% stenotic LAD lesion, the mild 40% stenotic lesion became the worst lesion in the main perfusion pathway of the middle and distal LAD index segments, whereas the 65% restenotic lesion in the second diagonal branch was the worst lesion in its perfusion path. If the randomization was CABG and the LAD graft was patent at 1 year, the new anastomotic (40% stenosis) lesion became the worst obstruction in the main perfusion pathway of the middle and distal LAD at follow-up in the example (Fig 1C). If the second diagonal graft was occluded, the 85% second diagonal stenosis remained the worst lesion in its main perfusion path. If the proximal circumflex lesion was <50% stenosis at baseline but became more severe than 50%, changing by at least 10% during follow-up, it would be measured as a new obstruction (Fig 1B).

Quantitative Coronary Arteriography
The primary measurement for each prospectively identified index segment was percent stenosis at the point of greatest obstruction in its main perfusion pathway. An index segment was considered successfully revascularized if this measurement was <50%. The point of greatest obstruction was identified visually; it was measured (in millimeters) at its narrowest point and at a visually selected, appropriate nearby normal diameter. Percent diameter reduction was calculated. If the main perfusion pathway included a bypass graft, the severity of the worst stenosis was estimated as the minimum diameter relative to normal arterial (not graft) diameter at or near the point of graft anastomosis to the native artery.

Cines were viewed at fivefold image magnification in a side-by-side overhead projection system that allows up to four films to be viewed simultaneously. This facilitates the analysis of identical arterial segments in comparable angiographic views. A single frame was selected at each protocol time point that clearly demonstrated a representative image of the segment of interest. The diseased segment was traced onto a standard form, together with a tracing of the catheter of known diameter for scale. Segments were measured from these tracings with a Macintosh II–based digital caliper system that provides scaled estimates of normal and minimum lumen diameters and percent diameter stenosis. These measurements are adjusted for pincushion distortion and out-of-plane selective magnification owing to x-ray beam divergence.^{21 22}

Primary Patient End Points (Arteriographic)
A scoring system was developed to reflect the degree to which successful revascularization had been accomplished per patient. This primary arteriographic end point was the proportion of a patient's index segments, specified before randomization, that were successfully revascularized (diameter stenosis <50%), as judged by QCA at the 1- and 3-year time windows. By this approach, in the follow-up examples of Fig 1, two of four (Fig 1B) and three of four (Fig 1C) index segments in the left coronary artery were successfully revascularized. Additional angiograms and procedures were required sometimes for symptomatic deterioration. Although measurements were obtained on all changing lesions in these clinically indicated (nonprotocol) films, the primary analysis did not consider these measurements unless they fell within the specified protocol time windows. Thus, a restenosis, redilated or bypassed at 4 months and widely patent at 1 and 3 years, represents a successful outcome at these two time points.

Statistical Analysis: Arteriographic Comparisons
Treatment groups were compared for baseline coronary anatomic and disease characteristics, frequency of complete revascularization, and degree of revascularization by ² tests for categorical variables and by pooled t tests for continuous variables.

The two randomized treatment groups were compared by pooled t tests in terms of the mean percent of designated index segments that were successfully revascularized (with <50% stenosis) at 1 and 3 years. The analysis was by intention to treat for those patients having complete arteriographic data to the 1- and/or 3-year time points.

Index segments were subclassified as high priority if they were supplied, at baseline, through high-priority index lesions. Such lesions were severely (70% to 95% stenosis) narrowed and were in large (2.5 mm) or proximal (LAD proximal to second diagonal branch, left circumflex artery proximal to the first major marginal branch, or RCA proximal to the posterior descending branch). The frequency of attempts and the success of revascularization of high-priority index lesions at protocol time points for various subgroups were compared by use of the above tests.

Patients with incomplete revascularization (at least one index segment supplied with 50% stenosis) were classified into moderate (50% to 69%) and severe (70% to 100%) stenosis on the basis of the worst outcome among all their index segments. PTCA and CABG patients with incomplete revascularization were compared in terms of the stenosis severity of their worst outcome by a pooled t test. The proportion of such patients with moderate or severe stenosis was compared by the ² test.

	Results

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Angiographic Characteristics
Table 1 shows baseline angiographic characteristics for 392 patients randomized to PTCA (n=198) or CABG (n=194).

View this table: [in this window] [in a new window]   Table 1. Baseline Angiographic Characteristics

There were 2.8±1.0 index lesions and 4.4±1.4 index segments per patient in the PTCA group and virtually identical numbers in the CABG group. Baseline index lesion stenosis severity averaged 71±7% per patient in both groups. The average proportion of index segments per patient for which revascularization was attempted in the baseline procedure(s) was 85% for PTCA and, judged from the operative report, 98% for CABG patients (P<.0001). However, for 2.1±1.6 index segments per patient classified as high priority, 96% were attempted in the PTCA group and 99% were reported as bypassed (P=NS).

Ejection fraction averaged 61±12 for PTCA and 62±12 for CABG patients. Twenty percent of PTCA and 16% of CABG patients had ejection fractions <50.

During follow-up, 85% of PTCA and 88% of CABG patients were recatheterized at 1 year. Three-year angiograms were completed for 77% of PTCA patients and 75% of CABG patients. Reasons for failure to complete protocol angiography are detailed in Table 2. Patients who failed to complete the angiographic follow-up (Table 3) were somewhat older (64 versus 61 years, P<.01) and more frequently female (36% versus 23%, P<.05) than those who finished. Otherwise, patients who failed to complete angiographic follow-up were indistinguishable from those who finished in terms of the baseline clinical and angiographic characteristics listed in Table 3.

View this table: [in this window] [in a new window]   Table 2. Failure to Complete Protocol 1- or 3-Year Angiography

View this table: [in this window] [in a new window]   Table 3. Baseline Clinical and Angiographic Characteristics for the Patients With Complete and Incomplete 1- and 3-Year Angiographic Follow-up

Analyses of Primary QCA End Point
After completion of the initial PTCA procedure(s) (Fig 4A), the mean percent per patient of index segments supplied by perfusion pathways with <50% stenosis was 71% (using QCA measurements). Of this 71%, 5% was attributable to additional procedures, mainly bypass surgery at this time point.

View larger version (43K): [in this window] [in a new window]   Figure 4. A, Differences in the mean percent of index segments revascularized (with percent stenosis [S] <50%) between PTCA and CABG at the protocol time points. The mean percent of index segments revascularized with QCA measurements was 71% for PTCA (the previously published 75%19 was determined with digital caliper measurements performed at Emory University Hospital) for PTCA and not assessed (N A) for CABG at baseline after the procedure. From operative reports, 99% of index segments were initially bypassed. Revascularization averaged 59% for PTCA vs 88% for CABG at 1 year (P<.001) and 70% for PTCA vs 87% for CABG at 3 years (P<.001). *Mean percent of index segments successfully revascularized through additional procedures. B, Differences in the mean percent of index segments free of severe stenosis (70%) between PTCA and CABG at the protocol time points. At baseline after the procedure, the mean percent of index segments free of severe stenosis was 96% for PTCA and not assessed (N A) for CABG. It was 90% for PTCA vs 95% for CABG at 1 year (P<.05) and 93% for PTCA vs 95% for CABG at 3 years (P=NS). *Mean percent of index segments free of severe stenosis as a result of additional procedures. F/U indicates follow-up. P<.001, P<.05 vs CABG group by t test.

Among patients studied at 1 year, the mean percent of successfully revascularized index segments was 59% for PTCA and 88% for CABG (P<.001). Contributing to these results were additional procedures (usually PTCA or bypass for restenosis): 17% for PTCA and 1% for CABG patients. The differences at 3 years were less striking but still highly significant (70% versus 87%, P<.001; 23% versus 2% of this was the result of additional procedures).

Revascularization Success With Various Disease Complexity
Patients were prospectively subclassified (Table 1) into four categories in terms of the number of vessels involved and complexity of disease: 29% had focal double-vessel disease (with only one lesion with 50% stenosis in each vessel), 31% had complex double-vessel disease (with at least one vessel having two or more lesions with 50% stenosis), 13% had focal triple-vessel disease, and 27% had complex triple-vessel disease.

As previously shown,¹⁹ for those patients randomized to CABG, the mean proportion of index segments revascularized was high in these four disease subsets (84% to 93%) at 1 and 3 years and did not depend on initial disease complexity, as was true for PTCA (56% to 66%) at 1 year. However, at 3 years after PTCA, success was greater among those patients without complex three-vessel disease (73% to 75% versus 56%, P<.03 by one-way ANOVA).

Complete and Partial Revascularization
A patient with all index segments successfully revascularized (free from residual stenosis 50%) was said to have complete revascularization. At 1 year, 30% of PTCA and 68% of CABG patients (P<.001) were so classified (Table 4). In 13% of PTCA and 4% of CABG patients, revascularization was incomplete because these procedures were not originally attempted for all index segments. Of completely revascularized patients, 11% of the PTCA and 1% of the CABG group achieved this status because of additional procedures for recurrent or persistent ischemia. At 3 years, results were similar, with complete revascularization in 44% of the PTCA and 66% of the CABG groups (P<.001). Again, a number (18%) of those with PTCA and few (4%) with CABG owed this success to additional procedures. Much of the improvement between 1 and 3 years in complete revascularization status among the PTCA group was due to repeated PTCA performed after the 1-year angiogram. Such procedures were performed if a target lesion could be linked to objective signs of ischemia. Patients also were categorized in terms of the percent of their index segments that were successfully revascularized (Table 4). The distributions of various degrees of revascularization success differed significantly between the two groups at 1 and 3 years (P<.001).

View this table: [in this window] [in a new window]   Table 4. Comparisons of Frequency of Freedom From Residual Stenosis 50% and 70% in Various Degrees of Revascularization Between PTCA and CABG at 1 and 3 Years

Revascularization Attempts and Success in Patients With High-Priority Index Lesions
As Table 5 shows, for patients randomized to PTCA, PTCA was significantly more likely to be attempted on high-priority index lesions (with 70% to 95% stenosis and located either in proximal segments or in large [2.5 mm] vessels) than on their lower-priority counterparts. However, the immediate success rate after PTCA was not significantly higher for high-priority index lesions (78% versus 70%, P=NS). For patients randomized to CABG, the chances for high-priority index lesions and their lower-priority counterparts to be bypassed were equal. For patients with high-priority index segments, the mean per-patient percentages of such segments successfully revascularized at 1 year were 64% for PTCA and 93% for CABG patients (P<.001). At 3 years, the difference was diminished but still significant (76% versus 89%, P<.01). Table 5 also identifies other index lesion morphological characteristics associated with attempted PTCA.

View this table: [in this window] [in a new window]   Table 5. Angiographic Correlates and Success Rate of Initially Attempted PTCA and CABG

Analyses Using an Alternative (<70% Stenosis) QCA End Point
Fig 4B compares PTCA and CABG in terms of the mean percent of index segments free of severe stenosis (<70%) at the protocol time points. At baseline, after initial PTCA procedure(s), the mean percent of index segments with <70% stenosis was 96%. Of this 96%, 6% was free of severe stenosis as a result of additional procedures, mainly bypass surgery at this time point. At 1 year, the mean percent of index segments free of severe stenosis was 90% for PTCA and 95% for CABG patients (P<.05). Contributing to these results were additional procedures, usually PTCA or bypass for restenosis: 22% for PTCA and 1% for CABG patients. At 3 years, there was no significant difference between PTCA and CABG in terms of the mean percent of index segments free of severe stenosis (93% versus 95%, P=NS).

Patients also were categorized in terms of the percent of their index segments free of severe stenosis (Table 4). The distributions of various degrees of freedom from residual stenosis 70% did not differ significantly between the two groups at 1 year but differed significantly at 3 years (P<.05).

Revascularization Failure: Frequency and Severity
A patient who at follow-up had at least one index segment with 50% stenosis was said to have failed to achieve complete revascularization. As Table 6 shows, 70% of PTCA and 32% of CABG patients (P<.001) were so classified at 1 year; at 3 years, 56% of PTCA and 34% of CABG patients with failed complete revascularization (P<.001). The mean stenosis severity of the worst outcome lesion among those patients with failed complete revascularization was 74% stenosis for CABG and 67% stenosis for PTCA patients at both 1 (P<.01) and 3 (P<.05) years. When patients with failed complete revascularization were classified as having moderate (50% to 69%) or severe (70% to 100%) stenosis based on the worst outcome among their index segments, there were significantly more PTCA than CABG patients in the moderate stenosis range (46% versus 15% of patients at 1 year, P<.001; 38% versus 16% of patients at 3 years, P<.001). But there was no difference between PTCA and CABG patients in the severe stenosis range (24% versus 17% of patients at 1 year, P=NS; 18% versus 18% of patients at 3 years, P=NS).

View this table: [in this window] [in a new window]   Table 6. Per-Patient Frequency, Extent, and Stenosis Severity of Most Severely Failed Index Segment Revascularization: Relationship to Initial Treatment Strategy and Protocol Time Point

	Discussion

Top Abstract Introduction Methods Results Discussion References

 
The answer to the question of whether to recommend an initial strategy of coronary angioplasty or bypass surgery for patients with multivessel coronary disease may depend, in part, on the outcome variables used to compare these strategies. In the prospective, randomized EAST protocol, the composite primary end point of the intention-to-treat analysis was the first occurrence of any of the following: death from any cause, interval Q-wave myocardial infarction, or a large reversible thallium defect detected at 3 years.¹⁸ The two treatment strategies did not differ in terms of these primary clinical end points.¹⁹ After 3 years, death occurred in 7.1% of the PTCA group and 6.2% of the CABG group (P=.7); Q-wave infarction in 15% versus 20% (P=.2); large thallium defect in 10% versus 6% of survivors (P=.2); and the composite end point of at least one of the above events in 27% versus 29% (P=.8). However, coronary angioplasty results in a trend toward more ischemia, whereas bypass surgery trends toward more nonfatal infarction.

Other EAST (secondary) end points include freedom from angina, angiographic status, cost, and the need for additional revascularization procedures. In this EAST report, we compare these two treatment strategies in terms of revascularization success, as determined from protocol QCA performed 1 and 3 years after the initial procedure(s). When compared in terms of the percent of jeopardized coronary index segments that are successfully revascularized (<50% stenosis), the strategy of initial CABG is significantly more effective than the PTCA strategy at both protocol time points. Revascularization success averaged 59% per patient with PTCA versus 88% with CABG (P<.001) at 1 year and 70% versus 87% (P<.001) at 3 years. A substantial portion of this revascularization in the PTCA group (17% and 23% at 1 and 3 years, respectively) was attributable to additional procedures. For the CABG group, revascularization was seldom (1% and 2% at 1 and 3 years, respectively) attributable to additional procedures.

Thus, there is an apparent paradox in the EAST results: the two treatment strategies do not differ in terms of the primary clinical end points but appear to differ substantially in revascularization success. We have examined these results in an effort to resolve this paradox. There were two main reasons for these between-group differences in revascularization. First, index lesion angioplasty was initially attempted in the perfusion pathway of only 85% of designated index segments. The reason is that the PTCA operators tended to dilate only those lesions judged to significantly contribute to ischemia, whereas the surgeon's approach was to provide complete revascularization.^{23 24 25 26 27 28 29} Consequently, virtually all (98%) index segments among CABG patients were initially grafted. This corresponds to current clinical practice. Surgeons generally attempt to graft as many distal arteries as possible, whereas PTCA operators commonly choose to dilate culprit or high-priority lesions, avoiding the procedural risks and questionable benefits for other milder lesions. For CABG, complete revascularization is considered superior to incomplete in terms of long-term clinical results,^{23 24 25 26 27 28 29} but this has not yet been proved for angioplasty in multivessel coronary artery disease. Some PTCA investigators recommend a selective high-priority lesion targeting strategy, as outlined above,^{30 31 32 33 34} whereas others favor a more complete strategy.^{35 36} MAPS³⁷ showed that angioplasty of stenoses <60% in coronary arteries 1.5 mm in diameter does not increase the clinical benefits attributable to dilating more severe lesions.

In EAST, revascularization was attempted in index segments supplied through high-priority index lesions in 96% of patients with PTCA and 99% of patients with CABG (P=NS; Table 5). Thus, selective lesion targeting was clearly practiced by the EAST angioplasty operators, whose decision to attempt initial dilation of an index lesion correlated highly with its severity (70% stenosis), proximal location, vessel size (2.5 mm), and number of index segments (two or more) supplied through the lesion. However, even among high-priority index segments, PTCA was still less effective than CABG, although treatment group differences were less pronounced (64% versus 93% at 1 year, P<.001; 76% versus 89% at 3 years, P<.01). Therefore, selective lesion targeting cannot entirely explain the paradox of no clinical advantage for CABG despite a revascularization advantage.

A second reason for the observed difference between groups in revascularization relates, in a subtle way, to differences in the mechanisms and magnitude of residual stenosis in those failed index segments with 50% stenosis. Fig 4B and Table 4 help explain the paradox described above. When PTCA and CABG were compared in terms of the mean percent of index segments free of severe stenosis (70%), there was a small but significant difference (90% versus 95%, P<.05) at 1 year and no difference at 3 years (93% versus 95%, P=NS). Furthermore, the frequencies of patients with all their index segments free of severe stenosis (70%) were comparable between PTCA and CABG at 1 year (76% versus 83%, P=NS) and identical at 3 years (82% versus 82%). The data of Table 6 also support this idea. Protocol angiography at 1 year showed at least one index segment supplied through a stenosed (50%) perfusion pathway in 118 PTCA patients (70%) and 54 CABG patients (32%). These segments were not considered successfully revascularized, although in many cases associated ischemic symptoms and/or reversible thallium defects were absent. With no evidence for ischemia, these anatomically stenosed revascularization attempts were seldom redilated or bypassed and usually persisted as 50% stenosis at 3 years (Fig 4B). This was particularly true for patients in whom the worst index segment outcome was only in the moderate stenosis range (50% to 69%). Only 21 (20%) of these patients had associated angina, interval myocardial infarction, and/or a large reversible thallium defect. In contrast, 28 (41%) of patients with one or more severely stenosed (70%) segments had such evidence for myocardial underperfusion. Because of the nature of the procedure, failure of revascularization with CABG (usually by graft occlusion) tends to result in more severely compromised index segment perfusion than does failure with PTCA (usually by restenosis). As a result (Table 6), the worst failure at 1 year among the CABG patients averaged 74±16% stenosis versus 67±14% stenosis for PTCA patients (P<.01). Furthermore, 78 of 169 (46%) of the worst PTCA failures (per patient) were in the moderate range, versus 25 of 170 (15%) of the worst CABG failures (P<.001). The proportion of patients with severe stenosis (70%) does not differ between PTCA and CABG at both 1 and 3 years. Thus, patients in EAST have failed revascularization (at least one index segment with 50% stenosis) more frequently with PTCA than with CABG at both 1 and 3 years. However, PTCA failures are more often of the moderate type (50% to 69% stenosis) that are less frequently associated with symptoms or signs of ischemia and, being less likely to require further revascularization, tend to persist. In contrast, CABG failures, when they occur, tend to be more severe and thus more symptomatic. When PTCA and CABG were compared in terms of the presence of severe stenosis, there was a small and nonsignificant difference at 1 year (24% versus 17% of patients, P=NS) and no difference at 3 years (18% versus 18%, P=NS).

In summary, we find that a strategy of initial PTCA, weighted toward selective targeting of high-priority lesions (70% stenosis in large or proximal arteries), even though associated with the expected frequency of incomplete revascularization, procedural failure, restenosis, and requirement for repeat revascularization, can achieve a 3-year outcome that is comparable in important anatomic and clinical respects to the strategy of initial CABG. It has been shown in this EAST post hoc subgroup analysis that a comparable proportion of index segments supplied through high-priority lesions had revascularization attempted by each of the two strategies (Table 1) and that a comparable number of patients were free of severe stenosis (70%; Table 4) or had severely failed revascularization (Table 6) that would be more likely to provoke a large reversible thallium defect.^{38 39} This is generally consistent with the MAPS analysis.³⁷ These observations suggest that clinical outcomes comparable to those of surgery may be achieved by a judicious lesion targeting approach to angioplasty that emphasizes high-priority lesions that in EAST appear to make up 44% of the index lesion population and supply 48% of jeopardized index segments. If confirmed in a prospectively defined subgroup analysis in another study, this concept has important implications for the practice of angioplasty in patients with multivessel disease.

	Selected Abbreviations and Acronyms

 

CABG = coronary artery bypass graft surgery CASS = Coronary Artery Surgery Study EAST = Emory Angioplasty Versus Surgery Trial LAD = left anterior descending coronary artery MAPS = Multivessel Angioplasty Prognosis Study PTCA = percutaneous transluminal coronary angioplasty QCA = quantitative coronary arteriography RCA = right coronary artery

	Acknowledgments

 
This study was supported in part by a grant (RO-1 HL-33965) from the NHLBI, Bethesda, Md, and a grant from the John L. Locke, Jr, Charitable Trust, Seattle, Wash.

Received September 19, 1995; revision received December 4, 1995; accepted December 21, 1995.

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