Adjunctive radial artery grafts no better than SVGs in multivessel CABG

New long-term data from the CSP 474 study challenges some of the conventional wisdom about graft choice in CABG surgery and may fuel debate on recent guideline recommendations.

Presenting long-term mortality figures from the VA study at the European Association for Cardio-Thoracic Surgery (EACTS) 2022 conference last week, researchers showed that patients with multivessel coronary artery disease should use the radial artery instead if an additional graft was required a saphenous vein brought no survival advantage.

Despite the new results, however, surgeons should aim to perform multi-arterial grafts in patients with multivessel coronary disease whenever possible, researchers say, although surgical skill should inform decisions about optimal conduit.

“Yes, multi-arterial grafts should be encouraged, but they should be used in selected patients, in selected coronary targets, and by experienced surgeons,” lead investigator Faisal Bakaeen, MD (Cleveland Clinic, OH) told TCTMD. “If you work in your center with radial grafts or arterial grafts such as the right internal thoracic artery, please continue to use it as the surgeon’s experience is an important factor in the results.”

But if surgeons use a saphenous vein graft instead for whatever reason, these late CSP 474 data suggest survival is not compromised.

Implications of the Policy

The latest European guidelines for myocardial revascularization recommend a strategy involving multiple arterial grafts in appropriately selected patients, with the additional arterial graft, typically the radial artery, being preferred over the saphenous vein after an initial left internal thoracic artery (LITA) for LAD (class I, level of evidence B) . Bilateral internal thoracic artery transplantation is also recommended when patients are not at high risk for sternal wound infection (class IIa, level of evidence B).

Graft choice has been more controversial in United States guidelines, where the Society of Thoracic Surgeons and the American Association for Thoracic Surgery (AATS) recently declined to support the 2021 Guidelines for Coronary Artery Revascularization proposed by the American College of Cardiology (ACC), the American Heart Association (AHA), and the Society for Cardiovascular Angiography and Interventions (SCAI), in part due to the Class 1 recommendation that the radial artery should be used in preference as an adjunct to CABG -Line in multivessel CAD. The STS position is that if a second arterial graft is needed in addition to the LITA-to-LAD graft, it should be either the right internal thoracic artery or the radial artery, although the strength of this recommendation is muted ( class IIa, level of evidence B ).

As Bakaeen explained to TCTMD, “If you give something a Class I recommendation, it becomes the standard of care, but it’s not a generalizable standard of care.”

No difference in mortality at 17 years

CSP 474 originally included 757 patients (mean age 61 years, 99% male, 90% white) who underwent elective CABG surgery between 2003 and 2009 at 11 Veterans Affairs (VA) medical centers in the United States. In all surgeries, the LITA was used to graft the LAD whenever possible, and the other vessels were grafted with either the radial artery or the saphenous vein. Almost 60% of the secondary grafts involved either the radial artery or the saphenous vein to the circumflex artery, while slightly less than a third involved the right coronary artery.

The primary endpoint of the original study – angiographic graft patency at 1 year – showed that there was no difference between the two procedures. For this follow-up analysis, the researchers evaluated long-term mortality in 733 patients and showed that there was no significant difference in the risk of all-cause mortality between those who received a radial artery graft and those who received a vena- saphenous graft (HR 0.99; 95% 0.8-1.2).

In a 5-year analysis of graft patency assessed with angiography in a subset of 196 patients whose grafts were patent at 1 year, occlusions were observed in three patients treated with a radial artery and two with a saphenous vein.

Bakaeen said the VA database only allows them to look at all-cause mortality, which is both a strength and a weakness of the current study.

“We cannot rule out a potential long-term benefit of the radial artery when it comes to major adverse cardiovascular events because we did not have reliable data,” he said. “We also had no reliable data on continuity. The incomplete patency results we have appear to indicate a lack of signal regarding superiority of the radial graft, but we cannot say with certainty that we can rule out a radial advantage.”

Real patients in the VA study

In a patient-level meta-analysis published in 2018 known as the Radial Artery Database International Alliance (RADIAL), researchers showed that using the radial artery via the saphenous vein was associated with a 33% reduced risk of adverse cardiac events. In follow-up angiography, which was performed after an average of 50 months, the radial artery was associated with significantly lower occlusion rates than the saphenous vein.

Mario Gaudino, MD (NewYork-Presbyterian/Weill Cornell Medicine, NY), who led this analysis, told TCTMD that CSP 474 is the only study that showed no difference in graft patency at 1 year, i.e. the absence of a mortality advantage in long-term follow-up is not surprising.

He noted that radial artery use is associated with a lower risk of MI and repeat revascularization (28% and 50% reduction in the RADIAL meta-analysis, respectively), but was not associated with a difference in survival. Any potential mortality effect would be quite small or negligible, Gaudino said in an email, “since the status of a non-LAD target is unlikely to affect survival.” MI and repeat revascularization are important outcomes, he said, and “mortality alone doesn’t tell the whole story.”

Notwithstanding these CSP 474 data, Gaudino emphasized that the overall risk-benefit ratio of radial artery transplantation is very favorable and noted that the incidence of donor site complications is very low in contrast to the use of the right internal mammary artery.

Cardiac surgeon Stephen Fremes, MD (University of Toronto/Sunnybrook Health Sciences Centre, Canada) said that the radial artery should routinely be preferred to the saphenous vein “when used to treat a medium-sized, left-sided target vessel with a high-grade lesion or right-sided vessel with subocclusive disease.”

Patients must also be good candidates for radial transplantation, e.g. B. by adequate ulnar collateral circulation and a radial artery with a diameter of at least 2-3 mm on noninvasive imaging. Obesity, diabetes, and gender do not affect the decision to use the radial artery, but advanced chronic kidney disease and peripheral vascular disease are both contraindications. It’s also relatively contraindicated in patients with poor LV function, he said.

“Anatomically, the [radial artery] is usually constructed as an aortocoronary graft,” Fremes said in an email. “In this configuration, it can usually reach all coronary targets, but may not reach targets in the posterolateral region, on the opposite side of the heart from the ascending aorta. When used as a composite graft, it can reach all areas.”

In 2004, Fremes, along with first author Nimesh Desai, MD (Sunnybrook Health Sciences Centre), published a study This shows that the use of the radial artery was associated with a lower rate of graft occlusions compared to saphenous vein grafts. Fremes also noted that he was involved in the development of the ACC/AHA/SCAI guidelines for coronary artery revascularization. While the surgical societies chose not to endorse the guidelines, Fremes, who remains a listed co-author of the guidelines, believes they were ultimately correct in recommending a Class I radial artery (but not in some of the other controversial points).

VA study achieved excellent results

Bakaeen told TCTMD that studies of radial artery support over the saphenous vein for secondary grafts are mostly observational and that the randomized controlled trials conducted to date have been small and are conducted in centers where operators are experienced in radial artery transplants . These results, Bakaeen said, are not really generalizable to all practitioners, leaving some uncertainty about the relative merits of radial grafting. Adding to these concerns, most studies lacked robust event tracking and assessments, with only the RAPCO study developed to evaluate the results in the long term.

The CSP 474 study is the largest study to date and includes surgeons working in VA centers, making it generalizable to US practice patterns, he said. He noted that the 1-year patency rate for either radial artery or saphenous vein grafts was 89%, which is comparable to the results achieved by the best hospitals.

“No one can argue that these were suboptimal procedures or lower standard surgery,” Bakaeen said. “In fact, I think they received excellent surgeries.”

For Bakaeen, an ideal patient for a radial graft is a patient who is younger or has a life expectancy greater than 10 years, has a critically ill and critical non-LAD target, and whose anatomy favors radial artery harvesting. Using the radial artery to bypass a severe blockage is less likely to result in competitive flow, the phenomenon in which there is an equilibrium between residual flow through the native coronary artery and flow through the bypass graft at the anastomosis. Competitive flow, he said, is an important predictor of radial graft patency.