CABG Grafts: The Debate Beats On

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Source: minimallyInvasiveCABG_1328892700.jpg - CABG Surgery
Postoperative incision after MIDCAB.
For surgeons, understanding what approach is best during CABG surgery has created much debate. A large body of research has cropped up regarding vein harvesting, including a five-year study that showed endoscopic vein harvesting during CABG did not decrease survival or increase harm. Additionally, other data have suggested that using radial arteries during CABG could reduce graft occlusions and decrease the risk of vein disease when compared with saphenous vein grafts. Here are varied opinions on which strategies reduce complications.

Endo argument still open

Minimally invasive surgical approaches typically result in better patient satisfaction, cosmetic improvements and faster healing. Currently, using the endoscopic vein harvesting (EVH) approach during CABG has become routine; however, it is unclear whether this approach is optimal.

Despite the fact that saphenous vein harvesting often is used during CABG, data have linked the procedure to more total wound complications and incision pain, a prolonged recovery period and worse cosmetic results. EVH has been introduced as an approach to thwart these types of complications.

But, despite its benefits, utilization rates in the U.S. are sluggish. Some have blamed this on cost considerations, the technical difficulty of the procedure and its possible link to vein damage.

A study by Lopes et al linked EVH to vein graft failure and adverse outcomes post-CABG procedure (N Engl J Med 2009;361:235-244). In the study, 1,754 patients underwent EVH and 1,247 patients underwent open vein harvesting. Lopes et al reported higher rates of vein graft failure at 12 to 18 months in the EVH arm compared with the open vein harvesting arm, 46.7 percent vs. 38 percent, respectively. At the three-year follow-up, the endoscopic approach was linked to higher rates of death, MI or repeat revascularization.

But a recent study conducted by Niv Ad, MD, chief of cardiac surgery and director of cardiac surgery research at the Inova Heart and Vascular Institute in Falls Church, Va., and colleagues challenged these results when they found that open vein harvesting was linked to higher rates of adverse outcomes. Of the 1,988 study enrollees, 1,734 patients underwent CABG with EVH and 254 underwent CABG with open repair (J Cardiovasc Surg 2011;52[5]:739-748).

"We found no clinical complications during the study, including any alarming graft occlusions," Ad says. Major adverse outcomes occurred in 17.8 percent of patients in the EVH group and 25.2 percent of those in the open harvesting group.

"Endoscopic vein harvesting is better for healing and recuperation and also can decrease wound-site infections," Ad says. "We now think this is the approach to take because we have seen improvement at one end and no harm on the other."

Last year, Donald S. Likosky, PhD, associate director of cardiac surgery of the Northern New England Cardiovascular Disease Study Group in Lebanon, N.H., and colleagues from Dartmouth-Hitchcock Medical Center, looked at the trends of EVH across northern New England between 2001 and 2004. Of the 8,542 patients who underwent a CABG procedure, EVH was used 52.5 percent of the time.

"We found that the utilization of the endoscopic approach increased from 2001 to 2004 with about one-third of physicians using the endoscopic approach in 2001 and three quarters of physicians using the approach in 2004," Likosky says. However, registry data linked EVH to an increased risk of bleeding and revascularization (Circulation 2011;123[2]:147-153).

"Despite these concerns, endoscopic vein harvesting is now the preferred approach across medical centers today," Likosky says.

But for some, cost concerns remain a barrier. EVH may reduce infection and length of stay. Yet, Ad says that the cost per case may increase due to higher operating room costs.

Mixed reviews on radial artery grafting

At ACC.11, Fremes et al from Sunnybrook Health Sciences Centre in Toronto, found that radial artery (RA) use during CABG lowered the rates of complete graft occlusions and stenosis when compared with saphenous vein grafts. Five-year data trends showed that fewer RAs became partially occluded when compared with saphenous vein grafts, 12 percent vs. 18.8 percent, respectively. Complete occlusions occurred in 8.9 percent of RAs compared with 17.8 percent of saphenous veins.

However, Goldman and colleagues refuted this evidence, noting that surgeons may need to reconsider using RA grafts. Compared with saphenous vein grafts, RA grafts did not improve angiographic patency at one year (JAMA 2011;305[2]:167-174). Their multicenter, randomized trial evaluated 733 patients (366 in the RA arm and 367 in the saphenous vein arm). No statistical differences in graft patency were found at one year.

Goldman et al also reported no statistical difference in surgical costs. The researchers found that the total cost of the RA was $57,105 ($13,629 in surgical costs) and total cost of the saphenous vein was $54,681 ($12,484 in surgical costs).

While the approach is underutilized in practice, with less than 5 percent of current patients receiving an RA graft, many studies have shown RA grafting to be superior to saphenous vein grafting, says Thomas A. Schwann, MD, chief of cardiothoracic surgery at University of Toledo Medical Center in Toledo, Ohio.

Making a case

Recently, more surgeons are considering additional arterial grafts to enhance long-term results, says Schwann. This strategy often included the RA. "We have compelling evidence that the more arteries are used to revascularize coronary circulation during CABG surgery, the better the outcomes," Schwann says. "These data have shown that using two mammary arteries are better than outcomes using only one internal mammary artery."

There may be a downside to tapping both internal thoracic arteries, he adds. "This approach can increase wound complications and it is a more complex procedure," says Schwann. As an alternative, he and his colleagues have turned to using the RA in place of the second internal thoracic artery.

"We have consistently demonstrated that using the left internal thoracic artery, a radial artery, plus veins, improved long-term survival," Schwann adds.

In light of these outcomes, Schwann says he hopes that cardiovascular leadership, such as the Society of Thoracic Surgeons, will incorporate the use of multiple arterial grafting as a quality benchmark. "Patients will have an incremental benefit in terms of credible survival if we use multiple arterial grafts as opposed to a single arterial grafts, which the current guidelines suggest," he says.

The mammary artery is used during 95 percent or more of CABG procedures, Schwann notes. Surgeons at the University of Toledo Medical Center use the RA in nearly 80 percent of patients. "While we have found that tapping into the radial artery takes time, there is no steep learning curve and we see better outcomes," Schwann says.

The difference in costs also is inconsequential, according to Schwann, and RA is contraindicated only in patients with poor hand circulation, who may require dialysis of the upper extremities or who have heavy calcification or atherosclerosis.

Despite strong data, no new approaches have replaced the standard of care—using internal mammary artery and saphenous vein grafts. But more results showing positive outcomes could offset barriers to adopting the RA approach during CABG surgery.