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Ann Thorac Surg 2006;81:1239-1242
© 2006 The Society of Thoracic Surgeons

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Original article: Cardiovascular

Initial Impact of Drug-Eluting Stents on Coronary Artery Bypass Graft Surgery

^a Division of Cardiothoracic Surgery, Beth Israel Deaconess Medical Center Harvard Medical School, Boston, Massachusetts
^b Cardiovascular Division, Beth Israel Deaconess Medical Center Harvard Medical School, Boston, Massachusetts

Accepted for publication August 15, 2005.

^_* Address correspondence to Dr Liddicoat, Beth Israel Deaconess Medical Center, Department of Cardiothoracic Surgery, 110 Francis St, Suite 2A, Boston, MA 02215 (Email: john_liddicoat{at}bidmc.harvard.edu).

Presented at the Forty-first Annual Meeting of The Society of Thoracic Surgeons, Tampa, FL, Jan 24–26, 2005.

Adult cardiac surgery: To participate in The Annals of Thoracic Surgery CME Program, please visit http://cme.ctsnetjournals.org.

 

	Abstract

Top Abstract Introduction Patients and Methods Results Comment Discussion References

 
BACKGROUND: Drug-eluting stents (DES) reduce the incidence of restenosis after percutaneous coronary intervention and have been predicted to decrease the number of patients referred for coronary artery bypass grafting (CABG). The purpose of this study was to determine the impact of DES on the number and characteristics of patients referred for CABG.

METHODS: Drug-eluting stents were introduced at our hospital in April 2003 and reached maturity by June 2003. We compared our isolated CABG patients from the 12 months before the introduction of DES (year 1) with those from the 12 months after full implementation of DES (year 2).

RESULTS: In year 1, of 4,348 cardiac catheterization patients, 2,144 (49.3%) underwent percutaneous coronary intervention, and 432 (9.9%) had CABG. In year 2, of 3,986 cardiac catheterization patients, 2,027 (50.9%) had percutaneous coronary intervention, and 337 (8.5%) had CABG, representing a 14% reduction in proportion of cardiac catheterization patients referred for CABG (p = 0.021). Among CABG patients, there was no change in age, prevalence of diabetes, or prevalence of three-vessel disease; however, patients in year 2 were more likely to have left main coronary artery disease (year 1, 36% versus year 2, 44.5%; p < 0.02) and left ventricular ejection fraction greater than 0.50 (year 1, 45% versus year 2, 52%; p < 0.02).

CONCLUSIONS: The clinical introduction of DES was associated with a modest decrease in the percentage of cardiac catheterization patients referred for CABG. Of those referred for surgery, an increasing proportion had left main coronary artery disease and preserved left ventricular systolic function. Defining the role of DES versus CABG for coronary revascularization will require elucidation of the long-term outcomes of DES compared with CABG.

Periodically, technological developments impact the management of coronary artery disease (CAD). Historic technological advancements that have done so include coronary angiography, coronary artery bypass grafting (CABG), percutaneous coronary angioplasty, use of the left internal mammary artery for CABG, and intracoronary stenting. Recently, drug-eluting stents (DES) were released into the marketplace, and heralded as the next breakthrough technology in the fight against CAD.

Drug-eluting stents reduce the incidence of restenosis after percutaneous coronary intervention (PCI) compared with bare-metal stents [1, 2], and may prove to be a significant improvement in the percutaneous treatment of CAD. Better armed, cardiologists are expected to treat a broader range of patients with CAD. Consequently, this will influence the surgical treatment of CAD. The purpose of this study was to determine the initial impact of DES on the number and characteristics of patients referred for CABG.

	Patients and Methods

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Patients
Drug-eluting stents were introduced for clinical use (outside of research protocols) at Beth Israel Deaconess Medical Center in April 2003 after their commercial release. Initially there was limited product availability, which restricted their utilization. These issues were resolved, and DES were fully implemented by June 2003. We were granted institutional review board approval to query our institutional databases for all patients undergoing cardiac catheterization (CC), PCI, and isolated CABG for the 12 months before the introduction of DES at our institution (year 1: April 2002 through March 2003), and for the 12 months after full implementation of DES at our institution (year 2: June 2003 through May 2004). The remaining patients, who underwent CC but not PCI or CABG, were categorized as other (Table 1). This included patients who required no further therapy, medical therapy, or referral for a procedure other than isolated CABG.

Statistical Analysis
Categorical variables were compared using Fisher's exact test. Continuous variables were compared using Student's t tests. All statistical analyses were performed using SAS for Windows version 6.12 (Cary, NC). A two-sided p value less than 0.05 was required for statistical significance.

	Results

Top Abstract Introduction Patients and Methods Results Comment Discussion References

 
The procedural volume data are presented in Table 1. In year 1, of 4,348 CC patients, 2,144 (49.3%) underwent PCI, and 432 (9.9%) had CABG. In year 2, of 3,986 CC patients, 2,027 (50.9%) had PCI, and 337 (8.5%) had CABG. The remaining patients in both years required no treatment, were treated medically, or were referred for a procedure other than isolated CABG. Overall, there was a significant change in the manner patients were managed (overall p = 0.05). From year 1 to year 2, there was a 14% reduction of patients undergoing CC who subsequently underwent CABG (p = 0.02). During the same period, there was no significant change in the proportion of patients undergoing PCI (p = 0.16) and other therapies (p = 0.96).

The demographic data of those patients undergoing CABG are presented in Table 2. Among those patients undergoing CABG in year 1 and year 2, there was no significant difference in the preoperative risk factors of sex, age, or prevalence of diabetes. However, fewer patients had left ventricular ejection fraction less than 0.50 in year 2 compared with year 1 (year 1, 52% versus year 2, 45%; p < 0.02). Furthermore, from year 1 to year 2, there was no significant difference in the urgency for the need for CABG or the prevalence of single-vessel, double-vessel, and triple-vessel CAD. There was, however, a significant increase in the percentage of patients referred for CABG who had LMCAD (36% versus 44%; p < 0.02), although the actual number of patients with LMCAD decreased.

	Comment

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The management of patients with cardiovascular disease is rapidly evolving. In general, patients with isolated CAD are managed with medical therapy or with a therapeutic intervention such as CABG or PCI. The distribution of patients into these management categories is driven by a number of factors including patient outcomes, new technology, invasiveness of procedure, patient and physician preference, and so forth. During the past several years, refinement of techniques related to mechanical revascularization (ie, PCI and CABG) for CAD have resulted in improved patient outcomes and, subsequently, an increase in the number of patients undergoing therapeutic coronary artery interventions [3].

During this same period, technological advancements in PCI have resulted in reduced restenosis and a broader range of lesions that can be successfully treated, thereby shifting the focus of coronary artery intervention from CABG to PCI. Drug-eluting stents represent the latest weapon in the armamentarium to mechanically treat CAD. Their implementation will undoubtedly impact the balance of patients being treated for CAD.

Drug-eluting stents were introduced at our institution in April 2003 and reached full implementation in June 2003. During the next 12 months, there was a significant change in the management of patients with CAD. There was no real change in the proportion of patients undergoing CC being treated with therapies other than PCI or CABG; however, of those undergoing a coronary intervention, there was a significant decrease in the proportion of patients undergoing CABG.

Of the patients undergoing CABG in year 2, an increasing percentage had LMCAD, but there was no difference in the distribution of the branch CAD. Additionally, patients undergoing CABG in the post-DES era were less likely to have a reduced left ventricular ejection fraction. This is an important observation because it indicates that interventional cardiologists remain concerned about intervening with PCI on LMCAD. However, they are increasingly more likely to treat branch CAD regardless of the number of branches involved and the degree of left ventricular dysfunction.

The American College of Cardiologists and the American Heart Association have established criteria for class ifying the usefulness of a given procedure or treatment (Table 3) [4]. In 2004, these classification guidelines for CABG were updated. In general, the guidelines set forth the following clinical guidelines for CABG for patients with isolated CAD [5]:

Class I:

LMCAD 50%

Anatomically equivalent LMCAD with 70% proximal left anterior descending coronary artery and left circumflex artery

Triple-vessel CAD, particularly in the setting of impaired left ventricular ejection fraction

Class II:

Proximal left anterior descending coronary artery stenosis; however, if left ventricular ejection fraction is impaired, becomes class I indication

One-vessel or two-vessel CAD, not involving the proximal left anterior descending coronary artery, if a large area of viable myocardium is at risk

Class III:

One-vessel or two-vessel CAD, not involving the proximal left anterior descending coronary artery

CAD without evidence of significant revascularizable viable myocardium

Study Limitations
The limitations of this analysis include all those inherent to a retrospective, single-institution study. There are also two methodological problems: (1) because we did not follow specific patients through the system, a patient who underwent CC on the last day of year 1 would have had their surgery during year 2, and (2) it is difficult to determine the exact date that DES became available at our institution in sufficient quantities and sizes to allow unfettered use. If the date was later than what we believed it to be, the impact of DES may have been underestimated. Finally, this study evaluates the initial impact of DES on the management of patients with CAD. Follow-up is required to determine the lasting effects of DES.

Clinical Inferences
In summary, the clinical introduction of DES correlated with a modest decline in the percentage of CC patients referred for CABG and a change in their clinical profile at our institution. Specifically, of those patients referred for surgery, an increasing proportion has LMCAD and preserved left ventricular systolic function. This trend may have been driven by new technology and early clinical results. Careful analysis of long-term outcomes is essential to determine whether this change in favor of PCI over CABG in clinical practice was justified.

	Discussion

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DR SELLKE: You stated that the proportion of patients with a normal ejection fraction, that is, greater than 50%, was actually increased in the latter years. Isn't that somewhat counterintuitive? I thought we were operating on sicker patients.

DR LIDDICOAT: I think that is true except the fact of the matter is when you look at the proportion of patients with left main disease, that increases, and that oftentimes offsets the reduction in ejection fraction. Looking at the class I indications as laid out by the ACC and AHA last year, left main coronary disease remains one of the three class I indications. I think when you look at the folks with left main coronary disease, they tend to have relatively more preserved left ventricular function.

DR TODD K. ROSENGART (Evanston, IL): Thank you for your presentation. A question for you: at your institution, were your cardiologists already enabled by existing technology or did you find that the drug-eluting stents enabled them to become more aggressive? In other words, there seems to be a pattern among cardiologists around the nation where at many institutions they were already performing essentially as many angioplasties as they could; other places they have become more aggressive with drug-eluting stents. Do you have any sense of what the pattern of change has been at your institution?

DR LIDDICOAT: The general philosophy of our cath lab has been to be very aggressive. Even in the pre–drug-eluting stents, having about 10% of those patients referred for CABG, I don't know exactly what the national average is, but it seems low. So I think that they were already enabled to be aggressive.

The drug-eluting stents in terms of a philosophical change has given them a little more data and a little more confidence in terms of the reduced restenosis rate to be even more aggressive.

	References

Top Abstract Introduction Patients and Methods Results Comment Discussion References

 

1. Moses JW, Leon MB, Fitzgerald PJ, et al. SERIUS Investigators Sirolimus-eluting stents versus standard stents in patients with stenosis in native coronary artery N Engl J Med 2003;349:1315-1323.[Abstract/Free Full Text]
2. Stone GW, Ellis SG, Cox DA, et al. TAXUS-IV Investigators One year clinical results with the slow-release, polymer-based, paclitaxel-eluting TAXUS stentthe TAXUS IV trial. Circulation 2004;109:1942-1947.[Abstract/Free Full Text]
3. Cardiovascular Procedure–Statistics. Available at http://www.americanheart.org/downloadable/heart/1103834461175FS19CVP5.pdf. Accessed January 18, 2005..
4. Eagle KA, Guyton RA, Davidoff R, et al. ACC/AHA 2004 guideline update for coronary artery bypass graft surgerysummary article. Circulation 2004;110:1168-1176.[Free Full Text]
5. Field JL, Pfeiffer H. Drug-eluting stentsassessing the impact on program volumes, profits, and future prospects. In: Comeau Stephanie, editor. Enterprise in Transition. Volume 1. Washington, DC: The Advisory Board Company; 2003. pp. 88.

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This Article Abstract Full Text (PDF) 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): John R. Liddicoat Sidney Levitsky Frank Sellke Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Liddicoat, J. R. Articles by Sellke, F. Search for Related Content PubMed PubMed Citation Articles by Liddicoat, J. R. Articles by Sellke, F. Related Collections Coronary disease