NEW YORK (Reuters Health) – Diabetes does not influence the long-term patency of coronary artery bypass grafts, according to a retrospective study.
“Both internal thoracic artery (ITA) and saphenous vein (SV) grafts have similar patency in diabetics and in non-diabetics,” principal investigator Dr. Joseph F. Sabik III, of Cleveland Clinic, told Reuters Health by email. “Since diabetics have more aggressive coronary artery disease (CAD) and a shorter life expectancy after coronary artery bypass grafting (CABG), my colleagues and I felt that long-term bypass graft patency was likely to be less in diabetics.”
Dr. Sabik and his team studied the long-term patency of 8124 ITA grafts and 20,376 SV grafts in 3881 patients with diabetes and 24,995 patients without diabetes. Participants were followed for up to 20 years after CABG.
Among patients with diabetes, 85% of ITA grafts and 47% of SV grafts were free of any stenosis on follow-up angiograms, compared with 86% of ITA grafts and 48% of SV grafts in patients without diabetes.
Only 4.6% of ITA grafts were occluded in patients with diabetes, compared with 6.7% of ITA grafts in patients without diabetes. Occlusions were more common with SV grafts (32% in patients with diabetes and 34% in patients without diabetes) than with ITA grafts, according to the August 1 online report from the Journal of the American College of Cardiology.
After adjustment for patient characteristics, study participants with diabetes had a significantly higher rate of early patency with ITA grafts than did participants without diabetes, but late ITA graft patency did not differ significantly by diabetes status. For SV grafts, early and late patency were similar between patients with diabetes and those without diabetes.
Risk factors for early graft occlusion included female sex, ITA grafting to the right coronary artery, and using an ITA graft for coronary arteries with a lesser degree of proximal stenosis.
Late-occlusion risk factors included younger age at the time of CABG, being asymptomatic, having a higher triglyceride level, SV grafting to the left circumflex coronary artery, and grafting to non-left anterior descending coronary arteries.
Despite similar long-term graft patency in patients with versus those without diabetes, long-term overall survival was significantly worse in the diabetic patients.
“Our observation that bypass grafts are just as effective in diabetics and non-diabetics demonstrates the value of CABG in diabetics with CAD and that their shorter life expectancy is likely due to other causes (such as secondary effects of diabetes),” Dr. Sabik said by email. “CABG is very effective in diabetics, and ITA graft patency is excellent (>90%), even in diabetics, 20 years after CABG. Whenever possible, ITA grafting with at least one, if not both, ITAs should be used in diabetics.”
Dr. David P. Taggart from University of Oxford, John Radcliffe Hospital, UK, who coauthored an editorial related to this report, told Reuters Health by email, “The seminal message of the current study is the differing patency of venous and arterial grafts, during two decades of follow-up. In contrast to an ongoing attrition of SV grafts (leading to a patency rate of around 40% at 20 years, similar in patients with and without diabetes), ITA grafts maintained patency in excess of 90% at 20 years.”
“No patients do better with SV than ITA grafts over the longer term,” he said. “In patients who have contraindication to use of both ITAs because of the potentially increased risk of sternal wound problems, then the radial artery should be preferentially used as a second arterial graft.”
Dr. Louai Razzouk from NYU Langone Medical Center, New York, who recently reviewed factors that should influence the choice between CABG and percutaneous coronary intervention in patients with type 2 diabetes, told Reuters Health by email, “This study showed that all patients, with or without diabetes, would benefit from at least one ITA bypass, as these conduits have the highest long-term patency (>90% at 20 years, in this and other retrospective studies).”
“The question, however, is who should be getting single versus bilateral internal thoracic artery bypass, as most patients get more than one artery bypassed at the time of the surgery,” he said. “The answer is that bilateral internal thoracic artery bypass should be avoided in obese women with diabetes and diffuse atherosclerotic burden, due to a higher risk of deep sternal wound infections, and needs to be individualized by the treating cardiac team in the rest of the population.”
“The other finding of the authors, which is that SV grafts have similar patency regardless of diabetes status, is really open for debate, as this was a self-selected group of patients who underwent angiography likely due to ischemic symptoms, and this may not be generalizable to all patients who have undergone CABG surgery,” Dr. Razzouk said. “A prospective study would be necessary to answer this question.”
SOURCES: http://bit.ly/2hhwlEw and http://bit.ly/2uOkaDV
J Am Coll Cardiol 2017
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