Multiarterial CABG ‘Underused’ in Contemporary Practice, Decreases Mortality

In contemporary US practice, CABG surgery is predominantly performed with a single arterial graft, a method that’s associated with increased mortality, MI, and repeat revascularization compared with using multiple arterial grafts, according to new observational data.

The study, led by Joanna Chikwe, MD (Smidt Heart Institute, Cedars Sinai Medical Center, Los Angeles, CA), and colleagues, was designed to overcome some of the hurdles seen in the ART trial—namely a high crossover rate and inconsistent surgeon experience. That trial showed no difference between patients randomized to CABG involving two internal-thoracic artery (ITA) grafts instead of a single arterial graft, plus vein or radial artery grafts, for a composite primary endpoint of death, MI, or stroke over 10 years.

Using a large registry is a way of “effectively eliminating” the problem of crossover, Chikwe told TCTMD. Also, “we selected surgeons that were much more appropriately experienced, and that's very important when you're comparing two surgical treatments, one of which is technically a little bit more demanding. The third aspect is that we were able to follow patients for longer. A lot of the important survival benefits you see in both device trials and surgical trials only really materialize out in long-term follow up.”

The findings were published in the November 5, 2019, issue of the Journal of the American College of Cardiology.

Multiarterial Lowers Mortality

Combining clinical registry data with New Jersey state records, the researchers included 26,124 patients who underwent isolated CABG between 2005 and 2012. The 14.0% of patients who received multiarterial revascularization were younger, were more likely to be male, and had a lower burden of comorbidity, including lower rates of diabetes, peripheral vascular disease, heart failure, and prior MI.

Overall, multiarterial CABG was associated with a lower mortality risk at 10 years compared with single-arterial operations (15.0% vs 26.0%; adjusted HR 0.84; 95% CI 0.76-0.92). This finding was confirmed in an analysis of 3,588 propensity-matched pairs (15.1% vs 17.3%; P = 0.01).

When patients were stratified by age, the multiarterial strategy maintained an edge over single-arterial CABG in those at most 70 years old (adjusted HR 0.87; 95% CI 0.77-0.99) but not in those older than 70 years (adjusted HR 0.91; 95% CI 0.75-1.1). Additionally, the survival benefit for multiarterial CABG remained when the propensity-matched analysis was restricted to surgeons who had performed at least 100 cases (adjusted HR 0.83; 95% CI 0.73-0.95). Findings lost statistical significance when only patients with ejection fractions of at least 30% were included (adjusted HR 0.95; 95% CI 0.68-1.3).

Multiarterial CABG was also associated with lower rates of MI in both the overall (6.7% vs 8.6%; adjusted HR 0.85; 95% CI 0.73-0.98) and propensity-matched cohorts (6.6% vs 8.1%; P = 0.02) compared with single-arterial CABG. Repeat revascularization was lower for multiarterial CABG in the propensity-matched cohort (11.5% vs 13.5%; HR 0.86; 95% CI 0.75-0.98), and stroke was lower in the overall analysis (4.1% vs 6.4%; P < 0.001).

“We were optimistic that we’d have enough numbers to see a really significant difference, which is exactly what we did,” Chikwe said. “We were impressed at quite how much of the survival benefit we saw was multiarterial versus a single-arterial strategy and also really interested to see that that didn’t quite hold up in the older patient group, so this is something that is really important for younger patients—patients under the age of 70.”

The total available evidence “really strongly supports a second arterial graft in patients that are younger than 70 that need multivessel surgical revascularization,” she observed. “In those patients who are older, a single arterial LIMA to LAD is absolutely appropriate and that makes me as a surgeon much more interested in hybrid approaches using a LIMA to LAD with PCI instead of vein grafts.”

Waiting for ROMA

In an accompanying editorial, David P. Taggart, MD, PhD (John Radcliffe Hospital, University of Oxford, England), who served as the PI for ART, writes that “the failure to use more than a single arterial graft during CABG has been attributed to predominantly three concerns: the increased technical complexity of revascularization using multiple arterial grafts; the potentially increased risk of mortality and major morbidity (particularly, sternal wound complications with the use of bilateral ITA grafts); and lack of supportive evidence from randomized trials to support a change in practice.”

These findings “should help guide decisions regarding the rationale for multiple arterial grafts and targeting this strategy to particular patient groups (eg, those younger than 70 years of age and those with good ventricular function),” but challenges endure, he argues. “The potential for confounding by unrecognized biases and the influence of surgeon experience remain to be resolved.”

Taggart points to the ongoing ROMA trial, which will randomize 4,300 patients to CABG with single or multiple arterial grafts where the second can be either an ITA or radial artery, as a study that will give “more definitive answers.” Those results won’t be available for several more years, but until then “the best available evidence still supports the use of multiple arterial grafts in appropriate patients and by appropriately trained surgeons,” he writes.

Speaking with TCTMD, Mario Gaudino, MD (Weill Cornell Medicine, New York, NY), the PI of the ROMA trial, said Chikwe and colleagues should be “commended for a great effort in this analysis” but noted this study shares the same limitations of past observational analyses.

“Because ROMA results will not be ready before 2025, I think that surgeons cannot ignore the signal that we have in favor of multiple arterial grafting, so [we] should probably try to switch toward a broader use of multiple arterial grafting but without increasing the operative risk,” he said.

Multiple arterial grafting can include a variety of techniques and conduits “and some of them are much more user-friendly than others,” according to Gaudino. “The radial artery, for example, is very versatile and easy to use. It's really not that different than using a vein. . . . It's fascinating to know that we have more evidence of a better patency rate for the radial artery than for any other conduits we use. So I think the radial artery should be the ‘first second’ arterial conduit, if I can use this wording.”

Chikwe and colleagues write that multiarterial CABG is “underused” in contemporary practice. To TCTMD, she suggested that one major reason why surgeons might avoid multiple arterial grafting is a “risk-averse approach that's driven by a focus on 30-day publicly reported outcomes that essentially acts against doing a more-involved operation where you only see the benefit 5, 8, and 10 years out.”

What might create change here is not only patient preferences and informed decision-making, but also pressure from referring cardiologists, she said. The latter is “what drove increased use of the LIMA to LAD 20-30 years ago, and that’s what will drive increased use of bilateral internal mammary artery revascularization and radial arteries now. One of the reasons we put this kind of surgical paper in front of a cardiology audience is because the cardiologists can be the drivers of change here.”

Also, Taggart writes, “there is increasing recognition that CABG should be recognized as a subspecialty within adult cardiac surgery, as has already happened for certain aspects of aortic and mitral valve surgery.” This kind of specialization will allow for surgeons performing CABG to become overall more proficient in the multiarterial approach, he notes. “Although not every surgeon needs to be facile with these techniques, every unit should have at least one surgeon who is, so that the most appropriate operation can always be tailored to the individual patient.”

Chikwe agreed. “It’s reasonable to expect that residents will get exposure to all [areas of cardiac surgery],” she said. “But in order to genuinely improve practice and patient outcomes at a national level, surgeon specialization—and targeting referrals appropriately to surgeons that you know who have specialist interest and expertise—is probably the critical strategy.”