Chronic stable angina percutaneous coronary intervention versus coronary artery bypass grafting

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Editor(s)-In-Chief: C. Michael Gibson, M.S., M.D. [1] Phone:617-632-7753; Associate Editors-In-Chief: Cafer Zorkun, M.D., Ph.D. [2]; John Fani Srour, M.D.; Smita Kohli, M.D.

Overview

PCI and CABG have become the standard of care in the management of patients with symptomatic coronary artery disease. Patients with multi-vessel disease, the overall mortality and freedom from myocardial infarction appear to be similar in both the treatment strategies; however, the need for repeat revascularization is significantly higher in patients who initially underwent PCI secondary to a higher incidence of restenosis.

PCI vs CABG

Limitations

Multiple trials have compared the strategy of initial PTCA with initial CABG for treatment of CAD. These large randomized trials were published in the mid-1990s. The findings from these studies constitute the primary source of data upon which clinical decision making has been made.

• The patients entered into these trials are poorly reflective of the general population (numerous patients were excluded and most included patients had preserved left ventricular function and focal atherosclerotic coronary disease).

• The initial trials are probably not relevant to current practice because of the lack of use of stents (especially drug eluting stents or DES) during PCI or of internal mammary artery rather than saphenous vein grafts during CABG. In addition, current antithrombotic regimens (eg, clopidogrel and glycoprotein IIb/IIIa inhibitors) were not employed during PCI.

PCI vs CABG for Isolated LAD Disease

There is great evidence that CABG of the LAD using an arterial conduit is associated with improved survival compared to medical therapy, especially if the LAD lesion is severe or associated with multi-vessel disease and/or left ventricular dysfunction. The internal mammary artery grafts are preferred because of the increases in long-term patency and survival compared to venous grafts. On the other hand, medical therapy can be considered for patients with isolated LAD disease with minimal evidence of ischemia on stress testing. In regards to percutaneous interventions on the LAD (usually PTCA with stent), this can be performed with a great success and low risk of complications in proximal LAD disease. However, surgical revascularization should be considered in more complex lesions such as ostial location, particularly with involvement of the distal left main, adjacent circumflex ostial disease, or complex bifurcation lesions involving a dominant first diagonal branch. Despite this low incidence of major complications with stenting of the proximal lesion, the need for revascularization is still lower with CABG than with stenting. This was illustrated in the SIMA trial (Stent versus Internal Mammary Artery grafting):

• SIMA trial: The SIMA trial involved 123 patients with a proximal, isolated LAD stenosis, and compared stenting using bare-metal stent (BMS) to CABG using an internal mammary artery. At 10 years, the incidence of death and myocardial infarction was identical; only the need for additional revascularization was significantly higher in the stent group. It is remarkable that no patients randomized to CABG required a second revascularization of the LAD.

The restenosis rate after PCI is likely to decrease with the increased use of drug-eluting stents (DES). In fact, clinical trials of sirolimus-eluting stents (SES) and paclitaxel-eluting stents (PES) have demonstrated a marked reduction in the incidence of restenosis in trials evaluating patients with both single and multivessel coronary disease:

• The RAVEL trial (A Randomized Comparison of a Sirolimus-Eluting Stent With a Standard Stent for Coronary Revascularization), is the first controlled trial of a coronary drug-eluting stent. The 5-year rate of target lesion revascularization (TLR) associated with SES was significantly lower than that with BMS.

• The role of drug-eluting stents in patients with LAD disease was evaluated in a post hoc analysis of data from the SIRIUS trial. Of 1101 patients enrolled in the original study, 459 had an LAD stenosis. All patients were randomly assigned to either a sirolimus-eluting stent or a bare metal stent. At eight months, the incidence of angiographic LAD restenosis was significantly lower among patients treated with a sirolimus-eluting stent (2 versus 42 percent). At one year, the incidence of major adverse events (death, MI, or target lesion revascularization) was also significantly reduced (10 versus 25 percent).

• Paclitaxel stent (PES): In 536 randomized patients with an LAD lesion in the TAXUS IV trial, at one year, the Paclitaxel stent was associated with significant reductions in target vessel revascularization (7.9 versus 18.6 percent) and the need for CABG (2.6 versus 6.3 percent).

• TAXi trial compared both types of drug-eluting stents: These stents were associated with very low rates of target lesion revascularization (1 and 3 percent at seven months). The three-year follow-up study, the TAXi-LATE trial, showed no difference in mortality of all causes in the PES and the SES groups (3% vs. 7%, P=0.98) or in major adverse cardiac event free survival (89% vs. 83%, P=0.28). Four stent thromboses were observed, two in the PES group (205 and 788 days) and two in the SES group (210 and 772 days).

Drug-eluting stents also appear to improve outcomes in patients with lesions at the origins of the LAD. This was illustrated in a study comparing sirolimus stents in 68 consecutive patients with such lesions to 77 patients treated with bare metal stents during the preceding two years. Positioning of the sirolimus stent into the distal left main trunk was required in one-third of patients for complete lesion coverage. The sirolimus stent was associated with significant reductions in angiographic restenosis at six months (5 versus 32 percent with bare metal stents) and target vessel revascularization at one year (0 versus 17 percent).

PTCA/PCI vs CABG for Multivessel Disease

• The two U.S. trials of PTCA versus CABG are the multicenter Bypass Angioplasty Revascularization Investigation (BARI) trial and the single-center Emory Angioplasty Surgery Trial (EAST).

In both trials, a majority of patients had two- rather than three-vessel disease and normal LV function. In the BARI trial, 37% of patients had a proximal LAD lesion. In the EAST trial, more than 70% of patients had proximal LAD lesions. The results of both these trials at an approximately seven to eight-year follow-up interval have shown that early and late survival rates have been equivalent for the PTCA and CABG groups. In the BARI trial, the subgroup of patients with treated diabetes had a significantly better survival rate with CABG. That survival advantage for CABG was focused in the group of diabetic patients with multiple severe lesions. In the EAST trial, persons with diabetes had an equivalent survival rate with CABG or PTCA at five years, after which the curves began to diverge but failed to reach a statistically significant difference at eight years (surgical survival 75.5%, PTCA 60.1%; p = 0.23). In both trials, the biggest differences in late outcomes were the need for repeat revascularization procedures and symptom status. In both BARI and EAST, 54% of PTCA patients underwent subsequent revascularization procedures during the five-year follow-up versus 8% of the BARI CABG group and 13% of the EAST CABG group. In addition, the rate of freedom from angina was better in the CABG group in both EAST and BARI, and fewer patients in the CABG groups needed to take anti-anginal medications.

A collaborative analysis of data from 10 randomized controlled trials (N= 7812) was pooled to compare effectiveness of CABG with PCI in view of long term effects on mortality in various clinical subgroups. PCI was done with balloon angioplasty in six trials and with bare-metal stents in four trials. The results showed that the long term mortality is similar with PCI and CABG in most patient subgroups who had multivessel disease. Based on this, the choice of the procedure should be made depending on patient's preference for other outcomes. CABG proved a better option in diabetics and elderly over 65 years.

• Non U.S. trials:

• RITA trial: The Randomized Intervention Treatment of Angina (RITA) trial was the first of the large scale trials to be published, involving 1011 patients from the United Kingdom. The long-term outcome of patients in the RITA trial (median follow up of 6.5 years) showed that the rates of death or nonfatal infarction for PTCA or CABG were the same (17 versus 16 percent). Angina was consistently higher in the PTCA group, 26 percent of whom required CABG, and 19 percent of whom required another PTCA. Repeat revascularization was usually performed within the first year, while the reintervention rate was 4 percent per year after the first three years.

• GABI trial: The German Angioplasty Bypass Surgery Investigation showed that both bypass surgery and angioplasty were equally effective in relieving angina at one year. This was associated with an increased rate of periprocedural morbidity with bypass surgery but more reinterventions with angioplasty.

• CABRI trial: The Europe-based multicenter Coronary Angioplasty versus Bypass Revascularization Investigation (CABRI) compared CABG to PTCA in 1054 patients. There was a similar mortality rate in the two groups at one year. However, patients assigned to PTCA required more repeat procedures and had a higher incidence of clinically significant angina. Restenosis after PTCA only partially accounted for this difference; of greater importance was the higher likelihood of residual disease after PTCA compared with CABG.

Stenting vs CABG for Multivessel Disease

The introduction of stents has resulted in a significant reduction of restenosis and of target vessel revascularization. 2 trials address this question: The ARTS and the SoS. However, these 2 trials did use bare metal stents and not the drug-eluting stents that further reduce the risk of restenosis. In addition, only few patients were treated with GP IIb/IIa inhibitors.

Bare Metal Stents

1205 patients were included in the ARTS 1 trial and were randomized to undergo bare metal stent implantation or bypass surgery. There was no difference in mortality (2.5 versus 2.8 percent at one year, 3.7 versus 4.6 percent at three years, 8.0 versus 7.6 percent at five years) or the rate of the combined end point of death, MI, or stroke for stented patients compared to those undergoing CABG. There was, however, a significant increase in the need for repeat revascularization with stenting (21 versus 4 percent at one year, 27 versus 7 percent at three years, and 30 versus 9 percent at five years). Diabetics and those with incomplete revascularization had the worse outcomes.

The Medicine, Angioplasty, or Surgery Study for Multivessel Coronary Artery Disease (MASS II), the Argentine Randomized Study of Coronary Angioplasty with Stenting versus Coronary Bypass Surgery in Patients with Multiple Vessel Disease (ERACI-II) and the Angina with Extremely Serious Operative Mortality Evaluation (AWESOME) showed similar survival rates but higher revascularization rates among patients with bare-metal stents at 5 years. Others (the Stent or Surgery trial; SoS) have shown a significant long-term survival advantage with surgery.

SoS trial: This trial included 988 patients between 1996 and 1999. At a median follow-up of two years, PCI was associated with a significantly higher rate of repeat revascularization (21 versus 6 percent) with CABG. At six years, mortality was significantly higher in the PCI group (10.9 versus 6.8; hazard ratio 1.66, 95% CI 1.08 to 2.55. Of note, there was a large number of death related to cancer in the stenting group.

Meta-analyses: Three meta-analyses published in 1995, 2007, and 2008 showed no significant difference between the PCI and CABG in all-cause mortality or cardiac death at one to five years, although angioplasty for multivessel disease was associated with a significant increase in mortality compared to CABG at five and eight years in a subgroup analysis.

Drug Eluting Stents

Data from randomized, controlled trials of drug-eluting stents as compared with bare-metal stents have shown significant reductions in the rate of repeat intervention, with similar rates of death and myocardial infarction. Studies comparing PCI involving drug-eluting stents with CABG have generally been smaller and nonrandomized.

• Sirolimus-eluting stents (SES):

In ARTS II study, the CABG-control group was a historical group from the ARTS I trial. As a result, conclusions should be made with caution. This trial demonstrated lower rates of revascularization and major adverse cardiac and cerebrovascular events (MACCE) with SES compared with BMS, as well as a higher rate of revascularization with equivalent MACCE to CABG at one year.

• Paclitaxel-eluting stents (PES):

The SYNergy between PCI with Taxus and Cardiac Surgery (SYNTAX): The SYNTAX trial is a prospective, clinical trial conducted in 85 sites that randomly assigned 1800 patients with three-vessel or left main coronary artery disease to undergo CABG or PCI (in a 1:1 ratio). A noninferiority comparison of the two groups was performed for the primary end point — a major adverse cardiac or cerebrovascular event (i.e., death from any cause, stroke, myocardial infarction, or repeat revascularization) during the 12-month period after randomization. The trial showed that the rates of major adverse cardiac or cerebrovascular events at 12 months were significantly higher in the PCI group (17.8%, vs. 12.4% for CABG; P=0.002), in large part because of an increased rate of repeat revascularization (13.5% vs. 5.9%, P<0.001); as a result, the criterion for noninferiority was not met. The study concluded that CABG remains the standard of care for patients with three-vessel or left main coronary artery disease.

A randomized trial is under way — the Future Revascularization Evaluation in Patients with Diabetes Mellitus: Optimal Management of Multivessel Disease (FREEDOM) study — that specifically compares drug-eluting stents with bypass surgery in patients with diabetes who have multivessel disease.