ACCEL | The national burden of cardiovascular disease caused by diabetes mellitus (DM) is increasing at an unprecedented rate. Currently, diabetes afflicts 25.8 million people in the U.S., with prevalence having more than doubled in the past decade and current estimates projecting an incidence between one in five in Americans by 2050. Results from SYNTAX (the Synergy between Percutaneous Coronary Intervention and Cardiac Surgery) and FREEDOM (Future Revascularization Evaluation in Patients with Diabetes Mellitus; Optimal Management of Multivessel Disease) trials confirm that coronary artery bypass graft (CABG) surgery is the preferred therapy for complex multivessel CAD, especially among patients with DM.

While CABG may be superior overall, there are variables that can further improve long-term outcomes associated with CABG surgery.

SITA vs. BITA

There is a substantial body of evidence demonstrating that the majority of patients benefit more when CABG surgery is performed with both internal thoracic artery conduits rather than just one. In one of the most recent studies of bilateral internal thoracic artery (BITA) grafting, late survival was significantly better with BITA versus a single internal thoracic artery (SITA) graft (13.1 vs. 9.8 years; p = 0.001), without any increase in perioperative morbidity or mortality.¹ However, as of 2013, only 5% of primary isolated CABG cases in the Society of Thoracic Surgeons National Adult Cardiac Surgery Database undergo BITA grafting.

Why are American surgeons doing so few BITA grafts? In an accompanying editorial comment,² John D. Puskas, MD, said U.S. surgeons are responding to their practice environment, especially to a fear of deep sternal wound infection in an increasingly obese, diabetic population of patients. While the study he was discussing found no significant difference, surgeons do pay a large and immediate political price for a deep sternal wound infection while receiving relatively little credit for the extra years that BITA grafting adds to a patient’s life.

Chair of Cardiothoracic Surgery at Mount Sinai Beth Israel, New York City, Dr. Puskas acknowledged that currently there is a relative financial disincentive to perform BITA grafting: incremental payment for the second internal thoracic artery graft is small considering the extra time required in the operating room. Moreover, CMS no longer reimburses for the extra care necessary for treatment of mediastinitis after cardiac surgery, because it’s now deemed a ‘never event.’ Thus, Dr. Puskas wrote, “Surgeons, who are increasingly employed by hospitals and hospital systems, are under intense pressure to perform CABG surgery that is safe and cost effective according to short-term metrics. Any perceived tradeoff, however small or misinformed, between the long-term benefit of BITA grafting and short-term risk of mediastinitis may discourage adoption of BITA grafting.”

As one of the co-authors of the ACCF/AHA guidelines for CABG surgery,³ Dr. Puskas noted that BITA is guideline-supported: “When anatomically and clinically suitable, use of a second IMA (internal mammary artery) to graft the left circumflex or right coronary artery (when critically stenosed and perfusing LV myocardium) is reasonable to improve the likelihood of survival and to decrease reintervention” (Class IIa; Level of Evidence: B).

At the 2014 New York Cardiovascular Symposium, Dr. Puskas pointed out that there are now 20 observational studies, with 70,897 patients analyzed in a pooled analysis indicating that BITA is associated with a significant reduction in long-term mortality relative to SITA (HR: 0.80; 95% confidence interval [CI]: 0.77-0.84).4 The benefit of BITA was increased in studies with a higher proportion of males.

Importantly, the available data suggest the significant advantage of BITA grafting is seen in patients with diabetes, too. For example, in that pooled analysis BITA grafting with complete revascularization seems to maximize long-term survival in diabetic patients undergoing CABG. Specifically, complete revascularization was associated with a 10% lower late mortality with no excess procedure-related effects.⁴

Indeed, patients deriving the greatest survival benefit (greater than a 23% 10-year survival difference) from the best surgical combination were actually the sickest of all: older women undergoing emergency surgery, with higher bilirubin, previous stroke, peripheral vascular disease, and insulin-dependent DM.

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References

1. Dorman MJ, Kurlansky PA, Traad EA, et al. Circulation. 2012;126:2935-42.
2. Puskas JD. Circulation. 2012;126:2915-7.
3. Hillis L, Smith PK, Anderson JL, et al. J Am Coll Cardiol. 2011;58:2584-614.
4. Takagi H, Goto SN, Watanabe T, et al. Thorac Cardiovasc Surg. 2014;148:1282-90.

Keywords: CardioSource WorldNews Interventions, Coronary Artery Bypass, Bilirubin, Cardiac Surgical Procedures, Cardiovascular Diseases, Centers for Medicare and Medicaid Services, U.S., Confidence Intervals, Coronary Artery Bypass, Coronary Vessels, Diabetes Mellitus, Mediastinitis, Myocardium, Percutaneous Coronary Intervention

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