RITA a Better Option Than Radial Artery for CABG

September 12, 2011

September 8, 2011 (Paris, France) The right internal thoracic artery (RITA) is a better vessel to use than the radial artery (RA) for multiple arterial revascularizations during coronary artery bypass surgery, results from a registry of 1000 patients suggest [1]. The findings were reported by Dr Elfriede Ruttmann (Innsbruck Medical University, Austria) at the European Society of Cardiology (ESC) 2011 Congress last week and published online September 6, 2011 in Circulation.

Ruttmann explained that the left internal thoracic artery (LITA)--also known as the left internal mammary artery (LIMA)--is established as the best vessel to use for bypass when only one is required and has been shown to reduce morbidity and mortality compared with saphenous vein grafts (SVGs). However, there is ongoing debate as to which is the best second conduit: although results have been conflicting, arterial grafts are thought to provide better long-term patency than SVGs, but it remains unknown which arterial conduit used as a second graft will provide the best long-term results.

"It has become very fashionable to use the radial artery, because it's easy to harvest--a physician's assistant can do this--but we know it has a high risk for vasospasm and it's not free from atherosclerosis, especially in diabetics," she explained.

It has become very fashionable to use the radial artery, because it's easy to harvest, but we know it has a high risk for vasospasm and it's not free from atherosclerosis.

But these new results--from by far the largest study comparing use of both thoracic arteries (bilateral internal thoracic arteries [BITA]) with the RA plus LITA--show that although the initial operation is longer and more technically demanding when BITA are used, this procedure generates better perioperative and long-term results, providing strong evidence for the superiority of a second internal thoracic artery compared with the RA, Ruttmann said.

Nevertheless, although propensity-matching was employed in this study, the patients were not randomized, and so a randomized, controlled trial is still needed to confirm these findings, she noted, adding that one is ongoing in Australia.

Propensity Matching Employed to Strengthen Results

Ruttmann and colleagues analyzed 1001 patients who underwent CABG at their institution between August 2001 and August 2010 and who received multiple revascularizations with a LITA graft and either a RITA or RA bypass as a second arterial conduit. There were 16 surgeons with at least six years of surgical experience who performed the procedures.

Of the patients, 277 received a RITA and 724 received an RA in addition to a LITA. Concomitant SVGs were grafted in addition as necessary. Propensity-score matching to generate a matched-pair patient subsample was used to reduce the impact of treatment selection in comparing RA and RITA as the second conduit.

The primary end point of the study was long-term overall survival and major adverse cardiac and cerebrovascular events (MACCE)-free survival.

In the full, unmatched patient population, overall survival was not significantly different between the two groups (p=0.054), but MACCE-free survival was significantly better in those who received both internal thoracic arteries compared with those who got an RA in addition to LIMA (p<0.001).

The propensity-score–matched approach also showed significant advantages of the RITA not only for the perioperative but also for the long-term outcome compared with the RA.

Overall survival (hazard ratio 0.23; p=0.022) and MACCE-free survival (hazard ratio 0.18; p<0.001) were significantly better in those who received both internal thoracic arteries compared with those who got an RA in addition to LIMA.

RA vs RITA: Perioperative Outcomes in Propensity-Matched Subgroup

Outcome BITA+SVG, n=277, n LITA+RA+SVG, n=277, n p
Aortic bypass anastomoses (mean) 1.1 2.3 <0.001
MACCE 4 21 <0.001
Perioperative MI 1 10 0.01
Perioperative stroke 1 10 0.01
Cardiac-related death 2 5 0.45

Radial Arteries Susceptible to Spasm and More Likely to Be Atherosclerotic

Ruttmann said the higher incidence of perioperative MI with RA is likely to be due to the known susceptibility of radial arteries to vasospasm. One of the chairs of the ESC session in which the study was presented, Dr David Taggart (University of Oxford, UK), said that in his institution, they now prepare radial arteries with phenoxybenzamine, which seems to have solved the problem of vasospasm.

And the lower incidence of stroke with the RITA compared with the RA almost certainly reflects less aortic manipulation when a second ITA graft is used, Ruttmann noted.

Likely the main reason for the long-term benefit of BITA grafting lies in the anatomic structure of the ITAs, which appear to be less susceptible to atherosclerosis than radial arteries, she said.

A postoperative angiographic substudy by her colleague Dr Nikolaus Fischler (Innsbruck Medical University), also presented at the ESC meeting, appeared to confirm this.

Fischler showed that 37.9% of radial arteries used in bypass became occluded or diseased compared with 10.2% of internal thoracic arteries and 20.9% of saphenous vein grafts.

Ruttmann et al report no conflicts of interest.

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