Study Supports Multiarterial CABG for Multivessel CAD

In patients with CAD in more than 1 vessel, multiarterial CABG provides better survival and lower reintervention rates through 9 years of follow-up than does PCI, whether with DES or BMS. The findings, from an observational study, were published in the September 29, 2015, issue of the Journal of the American College of Cardiology.

“The collective findings in our study, if confirmed in other series, have the potential to drastically modify the PCI vs CABG debate,” write Robert F. Tranbaugh, MD, of Mount Sinai Beth Israel Medical Center (New York, NY), and colleagues.

Multiarterial CABG has been shown to be superior to single-arterial surgical revascularization, they add. Thus, it “represents the optimal therapy for multivessel CAD and should be enthusiastically adopted by practicing cardiac surgeons and members of the multidisciplinary heart team as they strive to implement best evidence-based therapy,” they say.

Yet editorialist Robert A. Guyton, MD, of the Emory Clinic (Atlanta, GA), calls that conclusion “quite zealous” considering the limitations of the study.

Propensity-Matched Comparison

The researchers retrospectively examined information from cardiac surgery and interventional cardiology databases—spanning 1994-2011 and 1998-2009, respectively—at their center on 8,402 multivessel CAD patients undergoing their first nonemergency revascularization. Patients were divided into 4 groups according to treatment:

• PCI with BMS (n = 2,207)
• PCI with DES (n = 2,381)
• Single-arterial CABG (n = 2,289)
• Multiarterial CABG (n = 1,525)

All patients had significant LAD disease. Those who underwent multiarterial CABG received at least 1 radial artery graft in addition to a left internal thoracic artery-LAD graft, with or without additional vein grafts.

Over the study period, PCI was increasingly used as the primary means of treating multivessel CAD. BMS were used exclusively before 2003, and DES were used in the vast majority of PCIs by the end of the study. About three-quarters of DES-treated patients (77%) received first-generation devices, with second-generation stents used in the rest.

To account for substantial differences in patient characteristics across groups, the researchers used propensity matching. They identified the following comparison groups:

• 1,058 patient pairs for BMS vs single-arterial CABG
• 746 pairs for BMS vs multiarterial CABG
• 667 pairs for DES vs single-arterial CABG
• 546 pairs for DES vs multiarterial CABG

Multiarterial CABG Comes Out on Top

Through 9 years of follow-up, BMS use was associated with lower survival rates compared with both single-arterial CABG (66.7% vs 69.1%; P = .015) and multiarterial CABG (76.3% vs 86.9%; P < .001), whereas DES use was tied to worse survival only compared with multiarterial CABG (82.8% vs 89.8%; P < .001) in the propensity-matched cohorts.

Those patterns remained when looking at all-cause mortality risks after further multivariate adjustment, although the difference between single-arterial CABG and BMS fell short of statistical significance (table 1).

Within the first 3 years of follow-up, single-arterial CABG was associated with lower mortality relative to both BMS and DES. But after that point, mortality became equivalent in the CABG and BMS groups while becoming higher with single-arterial CABG vs DES.

Multiarterial CABG, on the other hand, was tied to reduced mortality relative to both BMS and DES in the first 4.5 years of follow-up. The advantage for CABG was attenuated beyond that point but still apparent.

Compared with both single-arterial and multiarterial CABG, PCI—regardless of stent type—was associated with higher reintervention rates through the entire follow-up period (P < .001 for all comparisons).

Accumulating Evidence to Back Multiarterial CABG

The ideal revascularization method for patients with multivessel CAD is still being debated. Results of randomized trials published in the past decade have mostly shown similar long-term survival with CABG and PCI, with more reintervention after PCI. “Yet these had limited applicability to the ‘real-world’ scenarios confronting clinicians, given the relatively healthy and highly selective nature of these trials’ populations,” Dr. Tranbaugh and colleagues say, adding that the trials compared only single-arterial CABG with PCI.

The “unique and important” finding of the current study that multiarterial CABG is tied to improved survival and less reintervention relative to both BMS and DES “represents a potentially game-changing perspective,” they argue, pointing to the even better outcomes achieved with multiarterial instead of single-arterial CABG.

The authors attribute the lower mortality risk seen with multiarterial—but not single-arterial—CABG vs DES to superior patency of arterial over saphenous vein grafts.

Critical Limitations

The authors acknowledge some drawbacks to their study, however, including its retrospective design; use of data from a single center; potential for confounding from unmeasured factors; and the lack of information on cardiac-related deaths, postdischarge medication use, and SYNTAX scores.

In his accompanying editorial, Dr. Guyton says the paper adds to growing evidence supporting the use of multiarterial CABG instead of a single conduit, but he also highlights “concerning limitations.”

Issues that have to be considered, he says, are whether the center in which patients were treated is representative of results elsewhere and whether patient-specific factors used to determine revascularization technique were “appropriately measured and recorded to allow reasonable risk adjustment of the 4 groups compared.”

Surgeons at Mount Sinai Beth Israel “have been champions of the radial artery as a second arterial graft” and employed “very aggressive use of multivessel stenting,” he notes.

But Dr. Guyton says the major problem with the analysis is that the coronary pathology used to decide on revascularization method “was neither measured nor recorded in the data available for statisticians to make appropriate adjustments.” Thus, he says, “no amount of statistical gymnastics can reliably adjust for this missing variable.”

Although the researchers’ overall conclusion is “correct,” Dr. Guyton writes, “it is justified by the weight of evidence from multiple studies, not the data and analysis presented.” He notes that the randomized ART study, which compares single-arterial vs multiarterial CABG, has completed enrollment and “will shortly help illuminate this issue.”

Sources: 
1. Habib RH, Dimitrova KR, Badour SA, et al. CABG versus PCI: greater benefit in long-term outcomes with multiple arterial bypass grafting. J Am Coll Cardiol. 2015;66:1417-1427.
2. Guyton RA. Multiple arterial coronary bypass grafting: likely better, but not yet a mandate [editorial]. J Am Coll Cardiol. 2015;66:1428-1430.

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• BEST: Due to Less TVR, CABG Still Favored Over PCI in Patients with Multivessel Disease
• CABG Shows Mortality Advantage over PCI in ‘Real-world’ Multivessel Patients
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