Risks of bilateral internal mammary artery bypass grafting

Abstract

Although use of one internal mammary artery (IMA) for coronary artery bypass grafting does not appear to be associated with increased risk, the results with both IMAs are less certain; the potential for a higher incidence of sternal wound infection as a result of devascularization of the sternum is a major concern. During a 42-month interval ending July 1988, 1,566 patients had coronary artery bypass grafting alone or in combination with other procedures: 633 received only vein grafts, 687 had unilateral IMA grafting, and 246 had bilateral IMA grafting. The IMA patients were younger, were more often male, had better cardiac function, and underwent fewer emergent, urgent, or combined procedures than the patients receiving vein grafts ( p < 0.05). Thirty-day mortality was lower among the IMA patients (unilateral IMA group, 2.8%; bilateral IMA group, 3.7%; and vein graft group, 7.9%; p = 0.001). With the exception of sternal wound problems, occurrence rates for postoperative complications among the IMA patients did not differ significantly from or were lower ( p < 0.05) than those among the patients with vein grafts. Sternal infections occurred with greater frequency among the bilateral IMA patients (6.9%) than among the unilateral IMA (1.9%) or vein graft (1.3%) patients ( p = 0.001). By univariate analysis, obesity, diabetee, bilateral IMA grafting, and need for prolonged (>48 hours) mechanical ventilation were associated with a significantly higher incidence of sternal infection ( p < 0.05). Multivariate logistic regression analysis identified use of bilateral IMA grafts ( p = 0.0001), obesity ( p = 0.0014), and prolonged mechanical ventilation ( p = 0.0018) as significant risk factors for the development of sternal infection. We conclude that bilateral IMA grafting is an important predictor of sternal infection. It should be used selectively in obese or diabetic patients and in patients who are likely to require prolonged mechanical ventilation postoperatively.