CABG Skyrockets Among Diabetics; Lessons for Heart Surgeons

Veronica Hackethal, MD

September 08, 2015

The proportion of diabetics who underwent coronary artery bypass grafting (CABG) jumped almost fivefold over the past 40 years, according to a recent single-center study covering over 57,000 patients at the Cleveland Clinic.

And although surgical outcomes have improved substantially, this combination of diabetes and heart bypass has become an excessively costly healthcare burden, as the results also show that diabetics have more postoperative complications and worse survival than nondiabetics, contributing to ballooning healthcare costs.

The study was published in the August issue of the Journal of Thoracic and Cardiovascular Surgery by Sajjad Raza, MD, of the Cleveland Clinic, Ohio, and colleagues.

"Diabetes is both a marker for high-risk, resource-intensive, and expensive care after CABG, and an independent risk factor for reduced long-term survival," says second author Joseph F Sabik III, MD, chair of thoracic and cardiovascular surgery and director of the cardiothoracic residency training program at the Sydell and Arnold Miller Heart & Vascular Institute, Cleveland Clinic.

The findings have important implications, not least for cardiac surgeons, say the authors and a number of accompanying editorialists. For example, surgeons will need to be more aggressive in performing certain graft procedures during coronary bypass surgeries in diabetic patients, they assert.

Diabetics: Worse Outcomes After CABG

The elevated risk for coronary artery disease (CAD) in diabetes factors highly into diabetes-related healthcare costs, which continue to rise substantially, totaling $548 billion worldwide in 2013, according to background information in the article.

Moreover, heart disease represents the major cause of death in diabetes.

While endocrinologists may be the physicians bearing the greatest responsibility for managing patients with diabetes, the disease is also having a tremendous impact on surgery, this new analysis shows, which included 10,362 patients with diabetes and 45,139 patients without the disease who underwent first-time CABG between January 1972 and January 2011.

The authors didn't discriminate between type 1 and type 2 diabetes; they used the presence (or absence) of pharmacologically treated diabetes mellitus (insulin or oral hypoglycemic agent) to categorize patients.

To account for the higher risk of cardiovascular morbidity and mortality in diabetics compared with nondiabetics, the authors used propensity matching to pair patients with those with similar risk profiles. Information on direct technical costs (excluding physician fees) came from the decision support services of Cleveland Clinic (corrected to 2011 dollars, and available from 2003 for 4679 patients).

Results showed that the proportion of diabetics who underwent CABG jumped from 7% in the 1970s to 37% in the 2000s.

Diabetics also had worse outcomes after coronary bypass compared with nondiabetics: more in-hospital deaths (2.0% vs 1.3%), more deep sternal wound infections (2.3% vs 1.2%), more strokes (2.2% vs 1.4%), more renal failure (4.0% vs 1.3%), and longer hospital stays (9.6% vs 6.0%), (P<.05 for all). Diabetics also spent more hours in the intensive care unit than nondiabetics.

Eleven percent of nondiabetic patients and 7.5% of diabetic patients received bilateral internal thoracic artery (ITA) grafts.

Hospital costs for diabetics were 9% higher than for nondiabetecs, mostly due to higher costs of clinical and laboratory testing and diagnostic imaging, as well as pharmacy and nursing costs. Diabetics were sicker and had more comorbidities, contributing to increased costs, the authors point out.

Diabetics also experienced worse survival after CABG than nondiabetics, and survival tended to diverge over time.

After propensity matching, 5-year survival was 80% in diabetics vs 84% in nondiabetics. But at 10 years, survival was 56% in diabetics vs 66% in nondiabetics. And at 20 years, it was 20% in diabetics vs 32% in nondiabetics.

After matching, diabetics still had longer hospital stays, as well as higher incidences of sternal wound infection and stroke, although cost differences between diabetics and nondiabetics were no longer significant.

Important Lessons for Surgeons About Types of Grafts

In a linked editorial published online, Drs Raza and Sabik — along with coauthor Eugene Blackstone, MD — discuss the implications of their study for surgeons, noting the need to optimize treatment and recommending bilateral ITA grafting '"to maximize long-term survival after CABG in diabetic patients."

Results from the FREEDOM trial, they note, established the superiority of CABG over percutaneous coronary intervention (PCI) in diabetic patients.

Worse long-term survival after CABG in diabetic patients, they add, is "likely due to more comorbidities than ineffectiveness of CABG."

Several other experts also weigh in.

In a second editorial, published in the August issue, Mani Arsalan, MD, and Michael Mack, MD, of the Baylor Research Institute in Dallas, Texas, say that despite "compelling evidence" about the benefits of bilateral ITA grafting for diabetics, the rates of this procedure are "distressingly low," both nationally as well as at the Cleveland Clinic.

"The use of skeletonized bilateral internal thoracic arteries in young, nonobese diabetic patients with a greater-than-10-year life expectancy is a reasonable risk to take," they assert.

"Perhaps in an elderly, morbidly obese female diabetic patient at high risk for sternal infection and shorter life expectancy, a single left internal thoracic artery would be best."

Other options to improve long-term survival after CABG in diabetic patients include using radial artery grafts and delaying elective procedures until glycemic control improves, they add.

Another expert, Paul Kurlansky, MD, assistant professor of surgery at Columbia University College of Physicians and Surgeons in New York, says arterial conduits may be the "optimal form of coronary revascularization [in diabetic patients]," in a third linked editorial, published in the August issue.

"Arterial conduits have greater long-term patency. The internal mammary artery [IMA], in particular, may be beneficial to the downstream vascular endothelium through the active secretion of nitric oxide," he commented.

"Although many surgeons have been reluctant to use the internal mammary artery in diabetic patients…several studies have documented that using a skeletonized approach to bilateral IMA grafting can be performed in diabetics without an increase in sternal wound infection, but with an improved long-term survival," he observes (Circulation. 2012;126:2935-2942).

Some evidence also supports using one IMA and one radial artery in diabetic patients, Dr Kurlansky continues.

"Given the incredibly low rate of bilateral IMA grafting in the United States — less than 5% in general, even less for diabetics — the surgical community is obligated to meet the rising challenge of the diabetic patient with the optimal therapeutic approach, which clearly supports arterial grafting," he emphasizes.

Prevention Is Better Than Cure

Dr Kurlansky adds: "The Cleveland Clinic study provides many important historical, clinical, and social insights. Their careful data analysis seems to have teased out the associated comorbidities from the mere fact of diabetes itself, to suggest that the incremental impact of diabetes, independent of associated risk factors, is not discernible in the early postoperative period, but rather takes an increasing toll on late mortality."

As such, diabetes is likely to remain a surgical concern for the foreseeable future, he notes.

Drs Arsalan and Mack agree: "The weight may be increasingly on our patients, but the real weight is on us as surgeons to help improve their early- and long-term survival."

Drs Raza, Blackstone, and Sabik, however, stress in their editorial that the ultimate solution lies in prevention.

"Clearly, policies and programs focused on controlling the factors that promote diabetes are critical to improving global public health and reining in the rising cost of healthcare," they emphasize.

"In the meantime, cardiac surgeons can play an important role in extending the lives of patients with diabetes by optimizing coronary revascularization, performing bilateral internal thoracic artery grafting with complete revascularization whenever feasible."

Dr Sabik reports being the North American principal investigator the Abbott Laboratories–sponsored left main coronary disease randomized trial (EXCEL), being on the board of directors for the Society of Thoracic Surgeons, and being on the scientific advisory board for Medtronic. The coauthors report no relevant financial relationships, nor do Drs Kurlansky, Arsalan, and Mack.

J Thorac Cardiovasc Surg. 2015;150:304-312, 313–314, 284–285, and published online July 16, 2015. Abstract, Kurlansky editorial, Arsalan, Mack editorial, Raza et al editorial


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