Marlene Busko

May 04, 2014

TORONTO, ON — Survival is improved when the right internal mammary artery (RIMA) rather than the radial artery (RA) is used as the second conduit when performing CABG for multivessel disease, a new study suggests[1]. A second study reports that total arterial revascularization provides better long-term survival than a single arterial graft[2]. The two studies were presented here at the American Association for Thoracic Surgery 2014 Annual Meeting .

"RIMA as a second conduit did not increase the operative risk, [including] sternal wound complications, and improved long-term outcomes, including survival, when compared with RA, [especially] among diabetic and obese patients," said Dr Shahzad G Raja (Harefield Hospital, London, UK), lead author of the first study.

"Total arterial revascularization . . . is associated with improved survival compared with only a single [internal thoracic (mammary) artery (ITA)] and saphenous vein [and] should be encouraged in all patients who have a reasonable prognosis," reported Dr Brian F Buxton (Epworth Hospital, Melbourne, Australia), lead author of the second study.


Quest for Best Conduit After LIMA

"I think we all agree that a left internal mammary artery [LIMA] graft to the left anterior descending [LAD] coronary artery is the gold standard," Raja said. However, the quest for the best arterial conduit to supplement LIMA continues.

RIMA is associated with superior long-term survival and freedom from intervention but is a technically demanding operation, and sternal wounds can be a problem. The RA is larger and easier to harvest and handle but is linked with arterial spasm and short patency, he noted.

The researchers analyzed data from patients who received a first-time CABG at their center from 2001 to 2013. Of the 1526 patients who had LIMA for the known LAD coronary artery target, 747 patients also received a RIMA and 779 patients received an RA graft to a non-LAD target. Some patients also received saphenous vein grafts.

In the propensity-score adjusted analysis, RIMA did not increase the incidence of 30-day mortality, deep sternal wound infection, or postoperative stroke, or the need for sternal rewiring, postoperative intra-aortic balloon pump, or renal replacement therapy. At a mean follow-up of 5.7 years, RIMA was associated with a reduced risk for late death.

Bilateral ITA Can Be Safe in Diabetes

"I don't really care which you favor for your second graft. I'm going to use the other one for the third and fourth arterial graft anyway," commented Dr Philip A Hayward (Austin Hospital, Melbourne, Australia), invited discussant of the study by Raja et al and a coinvestigator of the study by Buxton et al. "My practice is pretty much the same," Raja agreed.


"I think the most important part of your study . . . is the fact that in your series the bilateral ITA are almost entirely in situ rather than free grafts, and they are directed to the left circulation," Hayward noted.


Interestingly, patients with diabetes had a 25% survival benefit on top of the benefit from having RIMA vs radial-artery grafts. Patients who were obese had a 23% enhanced benefit.


"There are a lot of myths about the use of double internal mammary arteries among the cardiac surgery community," Raja said. "We were made to believe if you are diabetic you should not have double internal mammary [artery grafts]." But that evidence from 20 years ago is outdated because of improved diabetes management. "If you are very stringent with your glycemic control, you can safely do double internal mammary [artery grafts]." He does not perform these grafts on patients with previous radiotherapy to the chest or a body-mass index above 40 kg/m2.

To improve outcomes, like other surgeons at his institution, Raja uses a "double-wiring" technique to close the sternum. "I pour a lot of warm saline into the chest; I call it 'holy water,' " he added. "At the end of a procedure, I wash up all the chest with a liter or a liter and a half of warm saline . . . to remove debris. . . I feel the 'solution to pollution is dilution.' If you're aggressive, if you focus on minor things, you tend to get good outcomes."

Total Arterial Revascularization

Buxton and colleagues identified 3774 patients who underwent primary isolated CABG for triple-vessel CAD from 1995 to 2010. In this cohort, 2998 patients (78%) had total arterial revascularization and 786 patients (21%) received a single in situ ITA.

In the total arterial revascularization group, 2916 patients (97%) received at least an RA and 1079 patients (36) received bilateral ITA.

Using propensity-score matching, researchers identified 384 pairs. Major morbidities and 30-day mortality were similar for patients in both groups. However, survival at 15 years was higher in patients who had complete revascularization as opposed to a single arterial graft (54% vs 42%, respectively).

Invited discussant Joseph F Sabik III (Cleveland Clinic, OH) asked how many arterial grafts are enough. Hayward commented that the real question is "How many veins are enough?" In another study, they showed that "even adding one saphenous vein graft seems to be associated with a reduction in survival and progression of atherosclerosis," he said.

Buxton specified that, more recently, they tend to use bilateral ITA even in patients older than 70 years. They tend to put most grafts on the left side. When native coronary artery stenosis is above 70%, they may use the RA.

Buxton, Hayward, and Raja had no disclosures. Sabik receives grants/support from Edwards Lifesciences, Medtronic, and Abbott, honorarium from Medtronic, and is a consultant for Medtronic and ValveXchange


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