Artery-Only Grafts Beat Conventional CABG in Diabetes With CAD

Marlene Busko

July 18, 2016

In a large matched cohort of diabetic patients with advanced coronary artery disease (CAD) who had coronary artery bypass graft (CABG) surgery, those who had total arterial revascularization (TAR) had better long-term survival than those who had conventional CABG and similar perioperative complications.

The study by James Tatoulis, MD, department of cardiothoracic surgery, Royal Melbourne Hospital and department of surgery, University of Melbourne, Australia, was published online July 14 in the Annals of Thoracic Surgery.

Conventional CABG consists of three or four bypass grafts where one graft is the left internal mammary (thoracic) artery and the others usually all come from the saphenous veins in the legs, although a second artery may be used, Dr Tatoulis explained to Medscape Medical News.

TAR, however, uses only arteries, "generally one or two from behind the breastbone (the left and right internal thoracic artery) or both radial arteries from the forearm," he added.

In this study his team compared patients who had TAR (an average of 3.1 artery grafts) vs non-TAR/conventional CABG (an average of 1.6 artery grafts plus saphenous vein grafts).

The findings show cardiac surgeons that "you can do these slightly more complex operations with the same perioperative risk — about 1% for mortality and about 1% for each of the major complications of infection, bleeding, stroke, and perioperative MI," Dr Tatoulis said.

Second, the use of multiple arterial grafts translates into better survival — specifically, four more patients out of 100 are alive at 10 years (82 vs 78 patients), he added.

"Third, basically any reasonably well-trained cardiac surgeon is able to do this; they do each component in day-to-day practice, but most just don't do them all together," according to Dr Tatoulis.

"What we're saying is, if you're going to have a bypass and you're diabetic, then you're better off having total arterial or at least multiple arterial bypasses — the more arterial bypasses the better," he summarized.

CABG Better Than PCI, But Is TAR Better Than Usual CABG?

In general, diabetic patients with CAD do less well than other patients because their disease is more advanced, Dr Tatoulis said, adding that the large Future Revascularization Evaluation in Patients With Diabetes Mellitus: Optimal Management of Multivessel Disease (FREEDOM) trial clearly showed that for diabetic patients with CAD who underwent revascularization, CABG was tied to better long-term survival than stent implantation (percutaneous coronary intervention [PCI]).

Now, emerging evidence suggests that diabetic patients who do have CABG have better outcomes with multiple arterial grafts vs grafts of the left thoracic artery plus saphenous veins, because the patency "or chance that the bypass is working perfectly" 10 years after the surgery is more than 90% for internal mammary and radial artery grafts vs only about 50% for saphenous vein grafts, he explained.

However, TAR has not been widely embraced by cardiac surgeons. According to Society of Thoracic Surgeons (STS) data, only 5% of CABG done in the United States is done using TAR or multiple arterial vascularization. The rates in the United Kingdom and Europe are slightly higher (15%), and the highest rate is in Australia (45% to 50%).

About a third of patients who undergo CABG have diabetes.

Many surgeons are not comfortable using the two internal mammary arteries; "they're afraid of sternal malunion or infection, particularly in diabetics, and...they're not comfortable with taking out one of the two arteries in the forearm, which is unfounded," Dr Tatoulis notes.

The researchers aimed to compare outcomes of the two types of CABG in a large multicenter study in diabetic patients with CAD.

They identified 11,642 diabetic patients (of 34,181 patients) who had a first CABG during 2001 to 2012 and were part of the Australian and New Zealand Society of Cardiothoracic Surgeons (ANZSCTS) database.

From the database they derived a cohort of 2017 diabetic patients who had TAR and 1967 diabetic patients who had non-TAR/conventional CABG who were matched for age, sex, body mass index (BMI), and coronary and preoperative risk factors.

Same Low Perioperative Complications, Better Long-Term Survival

In the propensity-matched cohort, 1.2% of patients in the TAR group vs 1.4% of patients in the conventional CABG group died around the time of the surgery (P = .506).

Patients in both groups had similar low rates of major perioperative complications of stroke, MI, and multiorgan failure (< 1% for each) and septicemia (< 1.1%). Rates of reoperation because of postoperative bleeding were low and favored TAR (1.7% vs 2.5%).

Importantly, the rate of sustained deep sternal wound infection was low and similar in the TAR and conventional-CABG groups (0.8% vs 1.2%, respectively; P = .30), which highlights "that TAR can be achieved, even for diabetic patients, without compromising sternal integrity," the researchers stress. To minimize this complication, they used prophylactic antibiotics, tight perioperative glucose control (< 10 mmol/L), and other strategies.

During a mean follow-up of 4.5 years, fewer patients in the TAR than in the conventional-CABG group died (10.2% vs 12.2%; P = .04).

Moreover, "When people have multiple arterial grafts, not only do they live longer but...fewer will have a postop heart attack or be readmitted to the  hospital with heart failure or have further stents or further bypass surgery...thereby also reducing medical costs," Dr Tatoulis added.

Because "a mean of 3.1 arterial grafts could be placed expeditiously in the TAR diabetes group by a wide range of surgeons at several teaching hospitals...coronary artery grafting may not be as difficult a technical challenge as previously considered," he and his coauthors note.

Apart from the 30-minute longer time to harvest the arteries (which did not affect clinical outcomes), "we could not document drawbacks by using TAR in diabetic patients," they add.

Certain patients would not be suitable candidates for CABG with only artery grafts (such as very obese patients with a BMI > 45 kg/m2 [where one instead of two mammary arteries would be used] or the few patients who have a calcified, unusable radial artery), but they could still have CABG with multiple artery grafts, Dr Tatoulis explained.

This study indicates that "total arterial revascularization in large numbers of diabetic patients is achievable by senior trainees and attending surgeons in many institutions, with low perioperative mortality and morbidity, including [deep sternal wound infection] identical to conventional CABG but resulting in superior long-term survival," the researchers summarize.

"These findings will gain increasing importance with the progressive longevity of the population and the increasing proportion of diabetic patients who may require CABG," they conclude.

The authors have reported no relevant financial relationships.

Ann Thorac Surg. Published online July 14, 2016. Abstract

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