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Table 2-6. Diabetic Subgroup Results in Randomized Trials of CABG versus PCI

Study and

Treatment

Repeat

Mortality

Year

Patient Profile

Groups (N)

Revasc. (%)

o/ %

P Value

Comments

RITA-1, 1993

One- to three-vessel

CABG (33)

24.2 at 6.5 yr

.09

32% had single-vessel CAD; stents

CAD; angina or

PTCA (29)

6.9 at 6.5 yr

not used

ischemia

EAST, 1994

Multivessel CAD;

CABG (30)

10.0 at 3 yr

NA

Single-center study; stents not used

referred for revasc.;

PTCA (29)

6.9 at 3 yr

LVEF >25%

CABG

24.5 at 8 yr

.23

PTCA

39.9 at 8 yr

CABRI, 1995

Multivessel CAD;

CABG (60)

12.5 at 4 yr

NA

Stent use rare

angina or ischemia;

PTCA (64)

22.6 at 4 yr

LVEF >35%

BARI, 1996

Multivessel CAD;

CABG (180)

11.1 at 7 yr

19.4 at 5 yr

.003

81% IMA use; stents not used

angina or ischemia

PTCA (173)

69.9 at 7 yr

34.5 at 5 yr

CABG

25.6 at 7 yr

.001

PTCA

44.3 at 7 yr

ARTS, 2001

Multivessel CAD;

CABG (96)

3.1 at 1 yr*

3.1 at 1 yr

.294

89% IMA use; 3.5% glycoprotein

angina or ischemia;

Stent (112)

22.3 at 1 yr*

6.3 at 1 yr

IIb/IIIa inhibitor use

LVEF >30%

CABG

8.4 at 3 yr*

4.2 at 3 yr

.39

Stent

41.1 at 3 yr*

7.1 at 3 yr

CABG

2 7.5 at 5 yr*

8.3 at 5 yr

.27

Stent

42.9 at 5 yr*

13.4 at 5 yr

AWESOME,

Medically refractory

CABG (79)

35 at 1 yr*

19 at 1 yr

.27

54% stent use; 11% glycoprotein

2001

unstable angina;

PCI (65)

49 at 1 yr*

14 at 1 yr

IIb/IIIa inhibitor use

high CABG risk'

CABG

46 at 5 yr*

34 at 5 yr

.27

PCI

51 at 5 yr*

26 at 5 yr

CABG, coronary artery bypass graft surgery; CAD, coronary artery disease; IMA, internal mammary artery; LVEF, left ventricular ejection fraction; NA, not available; PCI, percutaneous coronary interventions; PTCa, percutaneous transluminal coronary angioplasty; revasc., revascularization. 'Combines absolute rates of repeat CABG and PCI.

'Prior heart surgery, myocardial infarction within 7 days, LVEF <35%, age >70 yr, or balloon pump use. 'Includes revascularization or unstable angina.

Adapted from Flaherty JD, Davidson CJ: Diabetes and coronary revascularization. JAMA 2005;293:1501-1508.

CABG, coronary artery bypass graft surgery; CAD, coronary artery disease; IMA, internal mammary artery; LVEF, left ventricular ejection fraction; NA, not available; PCI, percutaneous coronary interventions; PTCa, percutaneous transluminal coronary angioplasty; revasc., revascularization. 'Combines absolute rates of repeat CABG and PCI.

'Prior heart surgery, myocardial infarction within 7 days, LVEF <35%, age >70 yr, or balloon pump use. 'Includes revascularization or unstable angina.

Adapted from Flaherty JD, Davidson CJ: Diabetes and coronary revascularization. JAMA 2005;293:1501-1508.

rates of death, stroke, or MI were 25.0% with PCI and 19.8% with CABG. Diabetic patients treated with stenting had a lower event-free survival rate at 5 years (54.5%) compared with those undergoing CABG (25.0%) owing to the difference in the rates of repeat revascularization (42.9% versus 10.4%, respectively). The mortality rates did not differ (see Table 2-6). A comparison of the 1-year mortality rate among diabetic patients enrolled in the BARI (1996) and ARTS (2001) trials suggests an improvement in outcomes over time. The 1-year mortality rates in the two studies were 6.4% and 3.1%, respectively, with CABG and 11.2% and 6.3% with PCI. Such findings may reflect differences in patient selection or may indeed express an improvement in the revascularization and medical management of diabetic patients.

An indirect comparison between PCI and CABG results is also possible using registries. As an example, PCI outcomes of 857 BARI-eligible patients (23% with diabetes) treated within the NHLBI Dynamic Registry were compared with those of 904 patients randomized to PTCA in the BARI trial.78 Stents and GP IIb/IIIa antagonists were used in 76% and 24% of cases, respectively. A dramatic decrease in both abrupt vessel closure (1.5% versus 9.5%) and need for inhospital CABG (1.9% versus 10.2%) was observed in the more contemporary patient group. No difference in in-hospital mortality was observed. Among diabetic patients, the survival at 1 year within the group of BARI-eligible NHLBI Dynamic Registry patients was similar to that observed in the BARI-CABG group (92.1% versus 93.6%). However, such comparisons must be interpreted with caution, because the favorable outcomes of the registry patients may also be the result of improved medical management.

A registry conducted by the Northern New England Cardiovascular Disease Study Group evaluated 5-year mortality rates among patients undergoing revas-cularization procedures in a large regional database linked to the national death index.79 A subset of 7159 patients with diabetes treated between 1992 and 1996 was examined. Of those, 2766 patients (736 PCI and 2030 CABG) had similar profiles to diabetic patients randomized in the BARI trial. After adjustment for differences in baseline characteristics, patients treated with PCI had significantly higher mortality than those undergoing CABG (HR = 1.5). When stratified for severity of disease, the difference in mortality remained significantly higher for PCI in the setting of three-vessel but not two-vessel disease.79 Similarly, a single-center experience of 2319 consecutive diabetic patients (265 PCI, 2054 CABG) undergoing coronary revascularization in the late 1990s detected a significantly higher 5-year mortality rate

Table 2-7. Putative Explanations for the Survival Benefit of CABG over PCI in Diabetic Patients

More complete revascularization Less myocardium at risk on follow-up

Diabetes predicts restenosis after PTCA but not graft failure on follow-up

Less disease progression in untreated segments CABG may convey a survival benefit in the setting of subsequent Q-wave MI

Risk associated with repeat revascularization due to restenosis after PCI may negatively impact long-term survival

CABG, coronary artery bypass grafting; MI, myocardial infarction; PCI, percutaneous coronary intervention; PTCA, percutaneous transluminal coronary angioplasty.

with PCI versus CABG (adjusted HR = 1.7 for non-insulin-treated patients and 2.6 for insulin-treated patients).80

Further comparative analyses of the outcomes of diabetic patients undergoing CABG or multivessel PCI relied on databases of several New York cardiac registries. A total of 37,212 patients (33% with diabetes) undergoing CABG and 22,102 patients (25% with diabetes) undergoing stent-based PCI between 1997 and 2000 were indentified.81 At 3 years, a significant mortality reduction was observed among patients undergoing CABG, with the adjusted HR ranging from 0.59 to 0.71, according to the extension of atherosclerotic involvement. The observed reduction missed statistical significance only in the subgroup of diabetic patients with two-vessel CAD and no involvement of the left anterior descending coronary artery.

Explaining the Mortality Benefit of CABG

Several hypotheses have been formulated to explain the mortality benefit associated with CABG over PTCA suggested from the randomized trials (Table 2-7).74 The survival advantage of CABG among diabetic patients in BARI was limited to those who received at least one IMA graft. In addition, although diabetic patients in the CABG and PTCA groups had a similar mean number of significant lesions (3.5 versus 3.4), 87% of all intended vessels were successfully bypassed with CABG, but only 76% of vessels with significant lesions were successfully revascular-ized with PTCA.82 As expression of a less complete revascularization, in the BARI trial diabetic patients had more jeopardized myocardium after PTCA than after CABG.83 In addition, within the PTCA group, diabetic patients a had significantly higher increase in jeopardized myocardium at 1 year compared with nondiabetic patients. These findings are an expression of both restenosis and disease progression in untreated segments. In contrast, among CABG patients, diabetes was not associated with a percentage increase in jeopardized myocardium at angio-graphic follow-up.83

Furthermore, an analysis of all BARI-eligible diabetic patients (n = 641) revealed that the rate of Q-

wave MI in the first 5 years after revascularization was similar after PCI or CABG (approximately 8% to 9%), but at the same time the associated risk of death was substantially reduced in patients who underwent CABG (adjusted RR = 0.09).84 These results suggest that CABG provided greater protection from death after ischemic events in diabetic patients. Finally, whereas diabetic patients in the BARI trial had markedly greater restenosis after PTCA than nondiabetic individuals, graft patency in the CABG group was not influenced by diabetic status.85 The long-term survival advantage of CABG over PCI in diabetic patients may therefore, in part, result from having a more durable restoration of flow conveyed by CABG without the risk of a repeat revascularization procedure, as was frequently the case in the PTCA group.

CABG in the Era of Drug-Eluting Stents

So far, no study comparing DES implantation and surgery has been completed. Indirect information on the potential for DES to compete with CABG can be derived from the ARTS II study, a prospective multicenter registry of patients undergoing multivessel PCI with SES implantation, matched to the randomized patients included in the ARTS I trial of CABG versus stenting. In the subgroup of 367 diabetic patients, the 1-year MACE rate in ARTS II was 15.7%, similar to the rate in the CABG group of ARTS I (14.6%).86 There were no statistically significant differences in the rates of death (2.5% versus 2.1%), cerebrovascular accident (0% versus 5.2%), or MI (0.6% versus 2.1%), but a higher repeat revascularization rate was observed in ARTS II (12.6% versus 4.2%). Because occlusive restenosis occurs more frequently in diabetic patients than in nondiabetics and has been associated with increased long-term mortality among diabetics, DES treatment has theoretically the potential to improve survival in this patient popula-tion.87 It is encouraging that the mortality rate among diabetic patients at 1 year was 11.2% in the PTCA arm of BARI, 6.3% in the stent arm of ARTS I, and only 2.5% in ARTS II.86

A study sponsored by the NHLBI, the Future Revas-cularization Evaluation in patiEnts with Diabetes mellitus: Optimal Management of multivessel disease (FREEDOM) trial, will compare DES-based PCI and CABG in 2400 diabetic patients with multivessel disease. The primary end point will be all-cause mortality, nonfatal MI, and stroke. The study will have a parallel registry of approximately 2000 patients, and the overall study duration will be 5 years. In addition, the Coronary Artery Revascularization in Diabetes (CARDia) trial is currently randomizing 600 diabetic patients in the United Kingdom and Ireland to CABG or PCI (with either BMS or DES).88 The primary end point will be a composite of death, nonfatal MI, and cerebrovascular accident at 1 year. Additional data on costs, quality of life, and cognitive function are being collected, and follow-up will extend for 3 to 5 years.

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