Bilateral internal mammary artery grafts, mortality and morbidity: an analysis of 1 526 360 coronary bypass operations.

OBJECTIVES: The objective of this study was to investigate the impact of bilateral internal mammary artery (BIMA) on early outcomes after coronary artery bypass grafting.

DESIGN: Retrospective database analysis.

SETTING: US hospitals.

PATIENTS: 1 526 360 patients (mean age 65 years, 73% male) from the Nationwide Inpatient Sample from 2002-2008 who underwent isolated coronary artery bypass grafting with at least one internal mammary artery.

INTERVENTIONS: Single versus BIMA bypass grafting.

MAIN OUTCOME MEASURES: Inhospital mortality, deep sternal wound infection (DSWI).

RESULTS: The rate of BIMA use was 3.9%. Use of BIMA was independently associated with slightly lower inhospital mortality (unadjusted rate 1.1% vs 1.7%, adjusted OR 0.86, 95% CI 0.79 to 0.93). The DSWI rate was 1.4%. The independent predictors of DSWI were female gender (OR 1.06), congestive heart failure (OR 6.22), chronic pulmonary disease (OR 1.57), obesity (OR 1.17), diabetes mellitus (OR 1.04; OR 1.51 with chronic complication) and chronic renal failure (OR 2.13; OR 2.63 with dialysis). The use of BIMA was not an independent predictor of DSWI (OR 1.03, 95% CI 0.96 to 1.10). BIMA was associated with higher incidence of DSWI in patients with chronic complications of diabetes mellitus (OR 1.90, 95% CI 1.51 to 2.41).

CONCLUSIONS: BIMA grafting is associated with increased risk of DSWI only in patients with severe, chronic diabetes. The incremental morbidity and mortality of DSWI does not justify denial of BIMA in the majority of patients.