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Ann Thorac Surg 1997;64:3-7
© 1997 The Society of Thoracic Surgeons

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Original Articles: Cardiovascular

Predictors of CABG Within One Year of Successful PTCA: A Retrospective, Case-Control Study

Division of Cardiothoracic Surgery, Department of Surgery, and Cardiovascular Division, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts

	Abstract

Top Footnotes Abstract Introduction Material and Methods Data Collection Statistical Methods Results At Index Percutaneous... After "Index" Percutaneous... Multivariate Logistic Regression... Comment References

 
Background. We previously have established characteristics predictive of the need for coronary artery bypass grafting (CABG) over many years after successful percutaneous transluminal coronary angioplasty (PTCA). In this study, we examined the factors associated with the need for CABG within 1 year of successful PTCA, and the recent impact of newer, catheter-based technologies.

Methods. From January 1982 through December 1995, 234 patients underwent CABG within 1 year of a successful "index" PTCA at our hospital. Emergency operations within 12 hours of index PTCA were excluded. These cases were matched with 234 controls who underwent a successful index PTCA but did not require a subsequent CABG during the next year. Cases were matched by the date of their index PTCA, and 1-year follow-up was complete for all patients.

Results. Before index PTCA there were no differences between the groups in terms of age, sex, diabetes, prior myocardial infarction, ejection fraction, duration of anginal symptoms, hypertension, hyperlipidemia, family history, or obesity (all nonsignificant). At index PTCA the cases had a greater mean number of lesions measuring 70% or greater compared with the controls (2.8 versus 1.8, respectively; p < 0.0001). The cases were more likely to have critical (70% or greater) proximal left anterior descending artery, proximal first obtuse marginal artery, and right posterior descending artery stenoses. The use of stents or atherectomy devices was not significantly more common among the controls (21% of controls versus 17.1% of cases; p = 0.35). Complete revascularization was achieved in significantly fewer of the cases than the controls (91 versus 156, respectively; p < 0.0001).

The cases underwent CABG at a mean of 3 months (86% within 6 months) after PTCA. Among those who had a diagnostic catheterization, 52% of the patients had both restenosis of a dilated lesion and progression of other disease. Only 5 of 75 patients who had restenosis of a dilated lesion had a stent or an atherectomy device used at index PTCA. Of note, 13% (30 of 234) required an emergency operation, with an overall operative mortality rate of 3% (7 of 234).

Conclusions. Although the likelihood of local restenosis is decreased by newer interventional techniques, the need for CABG within 1 year after successful PTCA is not diminished. The number of critical lesions and their location are the best predictors of the need for early CABG. If early post-PTCA CABG is to be avoided, patients who cannot be completely revascularized by PTCA should be revascularized by CABG.

	Introduction

Top Footnotes Abstract Introduction Material and Methods Data Collection Statistical Methods Results At Index Percutaneous... After "Index" Percutaneous... Multivariate Logistic Regression... Comment References

 
See also page 7.

The need for operative coronary revascularization (coronary artery bypass grafting [CABG]) within 1 year of a successful percutaneous transluminal coronary angioplasty (PTCA) has significant economic and health care implications for patients with ischemic heart disease. We previously have established predictors of the need for CABG after successful PTCA in a cohort of patients who had CABG procedures performed at a mean of 16.7 months after successful PTCA [1]. These patients, however, had undergone PTCA between January 1982 and April 1989, with a minimum follow-up interval of 4 years. Characteristics that might predict the need for CABG within 1 year of PTCA have not been established.

All the patients reported in our previous study [1] had undergone conventional balloon PTCA (termed "plain old balloon angioplasty" [POBA] by our Chief of Interventional Catheterizations). Recently, however, the use of non-POBA techniques, such as atherectomy and stent placement, have become increasingly common. At our institution in 1994, more than half the patients who underwent PTCA had atherectomy or stent placement (485 non-POBA versus 410 POBA), and in 1995, the non-POBA techniques were used in 770 patients, compared with only 336 who had POBA. The impact of these techniques on the need for subsequent CABG, and on the interval to operation within 1 year, has not been studied.

In this study, we investigated whether predictors of the need for CABG within 1 year of successful PTCA could be discerned. Secondarily, we investigated whether use of the newer PTCA techniques was associated with a decreased likelihood of CABG within 1 year of those procedures.

	Material and Methods

Top Footnotes Abstract Introduction Material and Methods Data Collection Statistical Methods Results At Index Percutaneous... After "Index" Percutaneous... Multivariate Logistic Regression... Comment References

 
Population Studied
From January 1982 through December 1995, 234 cases underwent CABG within 1 year of successful PTCA at our hospital. These patients were among the 5,887 patients who underwent CABG operations during that period. They were selected by virtue of having undergone PTCA, which had been considered successful by our interventionalists, in the 12 months before their first CABG. The PTCA that preceded that CABG by 12 months or less was termed the "index" PTCA. When a patient had multiple PTCAs in the 12 months before CABG, the most temporally remote PTCA was considered the index PTCA. This term is meant to distinguish that particular PTCA from other prior or subsequent PTCAs.

The 234 cases were matched with 234 controls who underwent successful PTCA but did not require subsequent CABG during the next 12 months. The controls were matched solely by the date of the patient's index PTCA. One-year follow-up was complete for all patients.

Excluded from the study were patients who had emergency CABG operations associated with their index PTCA, those who had "unsuccessful" PTCA, and those who had PTCA after prior CABG. When no control PTCA was performed on the date of a case index PTCA, or when a potential control subject met exclusionary criteria, the PTCA with the next closest date was matched. When more than one control choice was available on a given case date, the match was selected randomly.

	Data Collection

Top Footnotes Abstract Introduction Material and Methods Data Collection Statistical Methods Results At Index Percutaneous... After "Index" Percutaneous... Multivariate Logistic Regression... Comment References

 
Case and control charts were reviewed for the following characteristics before index PTCA: age, sex, prior myocardial infarction, prior PTCA, diabetes, family history of coronary disease, obesity, smoking, hyperlipidemia, and hypertension. Each catheterization report was reviewed for left ventricular ejection fraction, number and location of lesions, percent stenosis of each lesion, number of lesions dilated, and PTCA complications. Over the year of follow-up after index PTCA, subsequent admissions, revascularizations, myocardial infarctions, and deaths were recorded. For patients, the interval to CABG, the number of vessels grafted, associated procedures, postoperative complications, and subsequent revascularizations also were recorded.

Completeness of revascularization by PTCA was assessed for each patient based on the concept that complete revascularization would require successful dilation of each lesion having 70% or greater luminal narrowing. Coronary anatomic assessment was that recorded by the treating invasive cardiologist. The term "total lesions" refers to all lesions, regardless of their severity, observed by the cardiologist. Angiographic reports obtained after the index PTCA were evaluated for progression of disease at the site of the PTCA, at other sites, or both.

	Statistical Methods

Top Footnotes Abstract Introduction Material and Methods Data Collection Statistical Methods Results At Index Percutaneous... After "Index" Percutaneous... Multivariate Logistic Regression... Comment References

 
Count data were compared by ² analysis. Means were compared by two-tailed Student's t tests and are expressed as plus or minus 1 standard deviation. Survival curves of equal-sized groups were constructed and analyzed by Mantel-Cox comparison, and curves for unequal samples were developed by generalized Wilcoxon comparison. We modeled the occurrence of CABG (cases) as a function of baseline data (before index PTCA) found to be significantly different from controls by univariate analysis. These data were analyzed by stepwise multivariate logistic regression analysis (True Epistat; Richardson, TX).

	Results

Top Footnotes Abstract Introduction Material and Methods Data Collection Statistical Methods Results At Index Percutaneous... After "Index" Percutaneous... Multivariate Logistic Regression... Comment References

 
Before "Index" Percutaneous Transluminal Coronary Angioplasty
There were no statistically significant differences between the cases and the controls in terms of mean age, male sex, incidence of diabetes, prior myocardial infarction, obesity, mean ejection fraction, duration of anginal symptoms, history of hypertension, hyperlipidemia, or coronary disease (Table 1). The cases had undergone significantly more PTCAs before their index PTCA than had the controls (0.78 ± 1 per case versus 0.53 ± 1 per control; p = 0.007).

	At Index Percutaneous Transluminal Coronary Angioplasty

Top Footnotes Abstract Introduction Material and Methods Data Collection Statistical Methods Results At Index Percutaneous... After "Index" Percutaneous... Multivariate Logistic Regression... Comment References

The mean number of lesions successfully dilated at the time of the index PTCA was 1.4 plus or minus 0.6 among cases and 1.3 plus or minus 0.57 among controls (p = 0.29). Morbidity after index PTCA occurred in 117 of 234 cases (50%) and 101 of 234 controls (43.2%) (p = 0.165). These complications included dissection, pseudoaneurysm, bleeding, packed red cell transfusion, dysrhythmia, infarction, dye reaction, renal failure, cardiac arrest, stroke, stent loss, vessel perforation, and early restenosis.

	After "Index" Percutaneous Transluminal Coronary Angioplasty

Top Footnotes Abstract Introduction Material and Methods Data Collection Statistical Methods Results At Index Percutaneous... After "Index" Percutaneous... Multivariate Logistic Regression... Comment References

 
CASES.
The 234 cases underwent CABG a mean of 3.02 months (range, 6 hours to 11.9 months) after their index PTCA. The interval to operation is depicted in Figure 1. Recurrence of angina or a positive exercise test was present in all patients before operation. Repeated catheterization was performed in only 89 of the 234 cases before CABG. Anatomic progression at the site of PTCA had occurred in 29 of 89 patients (33%), progression at sites other than the PTCA site in 12 of 89 (14%), and progression both at the site and elsewhere in 46 of 89 (52%). Neither restenosis nor progression was observed in 2 of 89 patients (2%) whose accelerated symptoms dictated CABG. New critical left main artery stenosis had developed in 14 additional patients (15.7% of the 89 who underwent catheterization before CABG).

View larger version (13K): [in this window] [in a new window]   Fig 1. . Operation-free survival for cases, showing the interval to coronary artery bypass grafting from index percutaneous transluminal coronary angioplasty.

There was no statistically significant difference in the interval to CABG between cases in which POBA was performed (mean, 2.9 months) and those in which atherectomy or stent procedures were performed (mean, 3.5 months; p = 0.72). These subgroups are seen in Figure 2. Among the 75 patients who had restenosis at the site of their index PTCA, 70 underwent POBA and only 5 underwent nonconventional techniques (one stent and four atherectomies). Complete revascularization at the index PTCA was not associated with a significantly longer mean interval to operation (complete, 3.02 months versus incomplete, 2.80 months; p = 0.171).

View larger version (18K): [in this window] [in a new window]   Fig 2. . Operation-free survival for cases stratified by technique of index PTCA. (POBA = plain old (conventional) balloon angioplasty.)

	Multivariate Logistic Regression Analysis

Top Footnotes Abstract Introduction Material and Methods Data Collection Statistical Methods Results At Index Percutaneous... After "Index" Percutaneous... Multivariate Logistic Regression... Comment References

 
Univariate analysis of baseline data primarily revealed angiographic predictors of CABG within 1 year of index PTCA, and the incidence of PTCA before the index PTCA was the only nonangiographic characteristic included in the analysis. The parameters selected by stepwise logistic regression analysis are shown in Table 3. The number of lesions measuring 70% or greater was the single best predictor, with an odds ratio of 1.55 for each lesion exceeding 70%. Lesion location also was an important factor predicting an increased likelihood of CABG within 1 year. Independent of the degree of stenosis, any observable lesion of the left main, proximal left anterior descending, or right posterior descending artery increased the likelihood of CABG within 1 year of successful PTCA.

	Comment

Top Footnotes Abstract Introduction Material and Methods Data Collection Statistical Methods Results At Index Percutaneous... After "Index" Percutaneous... Multivariate Logistic Regression... Comment References

 
The economic and health care implications of decreasing PTCA utilization in patients who will require operation within 1 year of their percutaneous intervention is obvious. Our previous study demonstrated that CABG performed after successful PTCA is associated with increased operative risk [1]. In that study, however, patients were followed up for 4 to 11 years after their PTCA, and their CABG operations were performed a mean of 16.7 months afterward. In this study, we focused on characteristics present before an index PTCA that would predict the need for CABG within 12 months of that procedure.

Every study of patients treated by PTCA is inexorably linked to the technology and pharmacology used during that study. As interventional technology and pharmacology advance, the conclusions of long-planned, prospective, interventional studies may be deemed less applicable. In 1995, nearly 70% of patients (770 of 1,106) who underwent PTCA at our institution had a stent or an atherectomy, and other institutions are reporting similar incidences of non-POBA PTCA [2]. Our previous retrospective study included patients who underwent only conventional balloon PTCA [1]. In the present study, however, nearly 20% had nonconventional PTCA (stent or atherectomy). Although the fraction of the PTCA-treated population has grown considerably, the case-control method used in this study allows for such a change in practice (less POBA and more new devices) by the temporal matching of patients who had successful PTCA followed by CABG within 1 year (cases) with those who had successful PTCA on the same data but did not require CABG within 1 year (controls). As the use of new devices has increased, if the technique were associated with a decreased likelihood of CABG within 1 year, there would be a greater prevalence of non–POBA-treated patients in the population who did not require CABG, and this would be reflected in the controls in our study, who are a sample of that population. Our data do not show a significant difference in the use of the new technologies in the controls compared with the cases (21% versus 17.1%, respectively). It is possible that a greater number of non–POBA-treated patients could make this about 4% difference statistically significant, but in the absence of refinements in device technology and device application, there is no reason to speculate that this modest difference in the use of non-POBA techniques between the controls and the cases would increase with a greater non-POBA prevalence.

A retrospective study such as this one provides a perspective different from that of other excellent prospective, randomized studies that have focused on the suitability of PTCA versus CABG for the initial treatment of multivessel coronary disease [3–6]. Each of these studies required a design that allowed only a defined subset of patients with multivessel disease to be enrolled. An examination of a general, less rigorously selected clinical population is complementary to our understanding of the interventional treatment of coronary disease. In the Emory Angioplasty Surgery Trial [4], for example, about 5,000 catheterized patients were screened, but only 842 were eligible for study entry. Of those 842 patients, only 392 actually were enrolled. Over the 5 years that these patients were followed up, 22% of those who had initial PTCA required CABG and 40% had additional PTCA. In the multicenter Bypass Angioplasty Revascularization trial [3], in which our institution participated, 1,829 patients with disease detected in two or more vessels by angiography were randomly assigned to undergo CABG or PTCA from August 1988 to August 1991. During this time, 2,013 eligible patients refused to participate. Over the 5 years of study follow-up, 31% of the patients treated with initial PTCA required CABG and 34% needed additional angioplasty. In contrast, only 1% of the patients treated with CABG required a second CABG and 7% required a subsequent PTCA. The slightly greater incidence of myocardial infarction and death among the patients who were treated with PTCA, particularly those with diabetes, was not a factor in our present, short-term study. We showed, in our previous study, that although diabetes is a predictor of the need for subsequent CABG, it is not associated with operation at an earlier interval [1].

Our case-control, retrospective study identifies specific criteria that a clinician may use to distinguish those patients with multivessel coronary disease who will do well with PTCA from those who will require CABG at an early interval. Using the criteria cited previously (e.g., three lesions measuring 70% or greater and a left main or proximal left anterior descending artery lesion), we identify a specific population of patients, 70% of whom will require CABG within 1 year of PTCA.

Our data also show that the newer interventional techniques are not associated with a decreased need for CABG within 1 year of their use. This suggests that other factors, such as those identified by our multivariate analysis (e.g., proximal left main or left anterior descending artery stenosis and number of lesions), are more predictive of the need for early CABG than is the technique of PTCA. The application of these data could decrease the number of interventional coronary revascularization procedures performed in a subset of patients with multivessel coronary disease, and thereby have a salutary impact on both their health care quality and cost.

	Footnotes

Top Footnotes Abstract Introduction Material and Methods Data Collection Statistical Methods Results At Index Percutaneous... After "Index" Percutaneous... Multivariate Logistic Regression... Comment References

 
Presented at the Thirty-third Annual Meeting of The Society of Thoracic Surgeons, San Diego, CA, Feb 3–5, 1997.

Address reprint requests to Dr Johnson, Beth Israel Deaconess Medical Center, 330 Brookline Ave, Boston, MA 02215.

	References

Top Footnotes Abstract Introduction Material and Methods Data Collection Statistical Methods Results At Index Percutaneous... After "Index" Percutaneous... Multivariate Logistic Regression... Comment References

 

1. Johnson RG, Sirois C, Watkins JF, et al. CABG after successful PTCA: a case-control study. Ann Thorac Surg 1995;59:1391–6.[Abstract/Free Full Text]
2. Lindsay J, Hong MK, Pinnow EE, Pichard AD. Effects of endoluminal coronary stents on the frequency of coronary artery bypass grafting after unsuccessful percutaneous transluminal coronary vascularization. Am J Cardiol 1996;77:647–9.[Medline]
3. The Bypass Angioplasty Revascularization (BARI) Investigators. Comparison of coronary bypass surgery with angioplasty in patients with multivessel disease. N Engl J Med 1996;335:217–25.[Medline]
4. King SB III, for the Emory Angioplasty Versus Surgery Trial: A randomized trial comparing coronary angioplasty with coronary bypass surgery. N Engl J Med 1994;331:1044–50.[Medline]
5. Hampton JR, and the RITA Trial Participants: Coronary angioplasty versus coronary artery bypass surgery: the Randomized Intervention Treatment of Angina (RITA) trial. Lancet 1993;341:573–80.[Medline]
6. Hamm CW, Reimers J, Ischinger T, Rupprecht HJ, Berger J, Bleifeld W. A randomized study of coronary angioplasty compared with bypass surgery in patients with symptomatic multivessel coronary disease. German Angioplasty Bypass Surgery Investigation (GABI). N Engl J Med 1994;331:1037–43.[Medline]

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This Article Abstract Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Robert G. Johnson Robert L. Thurer Frank W. Sellke William E. Cohn Ronald M. Weintraub Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Johnson, R. G. Articles by Weintraub, R. M. Search for Related Content PubMed PubMed Citation Articles by Johnson, R. G. Articles by Weintraub, R. M. Related Collections Related Article