An Unconventional Method

Using artery from the arm rather than vein from the leg leads to better outcomes after open-heart surgery on people struck by the double whammy of diabetes and advanced heart disease

More than 10 million Canadians are living with diabetes—a population that is at a higher risk for developing diseases of the heart and blood vessels. Coronary artery disease, the most common form of heart disease, is caused when arteries that supply blood flow to the heart muscle become blocked or narrow.

Tomorrow’s Heart Surgery—Now

  • On the other end of the intervention spectrum, cardiac specialists at Sunnybrook are pioneering minimally invasive techniques. Transcatheter aortic valve implantation (TAVI) is one of them.
  • TAVI replaces a diseased valve with an artificial valve that is inserted by a catheter through a small incision in the groin or chest, and threaded to the aortic valve in the heart.
  • TAVI is the “gold standard” for elderly patients with severe symptomatic aortic stenosis—narrowing of the aortic valve, which has a one-year mortality rate of 25% to 50%—for whom open-heart surgery is too risky.
  • Dr. Harindra Wijeysundera, an interventional cardiologist, was part of a 21-centre study that found TAVI to be safe and feasible in selected patients with bicuspid aortic valve, a congenital heart abnormality and the leading cause of aortic stenosis in patients aged under 65 years.
  • Wijeysundera, Dr. Stephen Fremes, a cardiac surgeon, and Dr. Sam Radhakrishnan, director of the cardiac catheterization labs, published the first study to evaluate the effect of delayed access to TAVI, shedding light on the impact of wait times on outcomes. Results showed that in high-risk surgical candidates a wait time longer than 60 days rendered TAVI less effective than conventional surgery.
  • Sunnybrook is one of five sites in Canada participating in the global Surgical Replacement and Transcatheter Aortic Valve Implantation (SURTAVI) study, which aims to recruit 2,500 patients. The goal is to assess if TAVI is a good option for people at intermediate surgical risk.
  • Fremes and Radhakrishnan are co-leading the SURTAVI trial at Sunnybrook. Participants will receive either a Medtronic CoreValve system or a surgical aortic valve replacement.

Coronary artery bypass grafting (CABG, pronounced “cabbage”) is considered the standard of care to help restore blood flow to the heart in people with diabetes and advanced coronary disease, compared to the less invasive percutaneous coronary intervention (PCI), or angioplasty. The procedure involves open-heart surgery during which doctors sew a healthy artery or vein from the chest or leg to the diseased vessel, thereby bypassing the blockage and rerouting blood to the heart. An important predictor of long-term success in CABG is persistent graft patency—the flow of blood through the graft to the heart.

Graft patency after CABG is important for everyone, but especially for patients with diabetes, who, after the procedure, are more prone to developing atherosclerosis, plaque buildup in and on the artery walls, and who have a higher mortality rate associated with coronary artery disease than do people without diabetes. In patients with diabetes, this same process can affect the bypass grafts.

Cardiovascular surgeons at Sunnybrook Research Institute (SRI) have already shown that using the radial artery, taken from the wrist or forearm, is a better choice than using vein grafts from the leg for patients with severe blockages.

Now, extending their findings, they have determined that the radial artery is associated with better long-term outcomes on graft patency for patients with diabetes compared to the conventional method using the saphenous vein from the leg or thigh.

“Diabetes is an important indication for bypass surgery. It was very important to look at the long-term effects because there are not many studies looking at CABG for long-term effects of diabetes, especially when you’re comparing arterial grafts,” says Dr. Saswata Deb, a resident in cardiac surgery and research fellow in the Schulich Heart Research Program at SRI.

Deb and his mentor Dr. Stephen Fremes, a scientist in the Schulich Heart Research Program and a cardiovascular surgeon at Sunnybrook, co-authored a study using data from the multicentre radial artery patency study (RAPS). The long-term RAPS study was the first Canadian randomized controlled trial to compare the radial artery with saphenous vein grafts in patients with and without diabetes.

Participants were 529 patients aged under 80 years undergoing open-heart surgery for a triple bypass, to open three blocked arteries. The aim was to determine the long-term impact of diabetes on radial artery and saphenous vein graft blockages. Each patient received angiography more than five years after CABG to evaluate the status of the bypass grafts. Angiography is a minimally invasive medical procedure to view blood vessels after injecting them with a dye that outlines them on X-ray.

Deb and Fremes reviewed a subgroup of the patient population who underwent late angiography: 269 patients, of whom 83 had diabetes. They found that five years or more after undergoing CABG, the radial artery is a much better choice for bypass grafting than is the saphenous vein in patients with diabetes.

Specifically, they found that in diabetics, 25.3% of patients who received a saphenous vein graft from the leg or thigh developed complete blockage of their vein graft, but only 4.8% of those who received a radial artery had completely blocked radial grafts. The results were published in The Journal of Thoracic and Cardiovascular Surgery in 2014.

Our goal is to provide evidence-based recommendations for the treatment of diabetic patients, so that they receive the most effective treatment.

“One study usually doesn’t change practice, but given the strength of our study, we think it definitely shows good evidence for it,” says Deb, the study’s lead author. “At the end of the day, everyone wants strong long-term results, so along with other studies that will be published soon, I think that the practice will shift.”

Subsequent studies include one looking at gender investigating how the radial arteries perform in men versus women. These types of studies are relevant as women are often overlooked in the cardiac arena because they tend to present symptoms later in age.

Fremes says implementing guidelines carries weight in changing medical practice. “Our goal is to provide evidence-based recommendations for the treatment of diabetic patients, so that they receive the most effective treatment,” he says. “The guidelines will be more persuasive than one individual study.” Fremes is a contributing author to the guidelines, which will be published later this year.

Moreover, the improvement in intraoperative and postoperative care globally has also affected practice, adds Fremes, such that patients who would have died 10 to 20 years ago are now surviving.

“In the developed world, cardiac surgery is declining in part because of primary prevention of coronary artery disease, but also because of less invasive ways—PCI—to treat what has been formerly treated with very invasive ways—CABG. However, patients with diabetes with advanced coronary artery disease remain a group that typically has better outcomes with bypass surgery than PCI,” he says.

In a growing diabetic population facing heart disease, Deb and Fremes are hopeful that the results of their study will provide other surgeons with the evidence they need to use arterial grafting, thereby improving long-term survival rates.

This research was supported by the Bernard S. Goldman Chair in Cardiovascular Surgery at Sunnybrook, held by Fremes, and the Canadian Institutes of Health Research.