Left internal mammary artery to the left anterior descending artery: effect on morbidity and mortality and reasons for nonusage.

Background: The left internal mammary artery to the left anterior descending artery is recognized as the gold standard for revascularization. Several studies have shown the benefits of the left internal mammary artery. However, a substantial portion of patients undergoing coronary artery bypass grafting does not receive this conduit. We sought to identify reasons for nonusage of the left internal mammary artery to the left anterior descending artery, while evaluating short- and medium-term outcomes.

Methods: Between April 1997 and September 2001 a total of 4406 consecutive patients underwent coronary artery bypass grafting with revascularization to the left anterior descending artery. All data were collected prospectively except reasons for nonusage of the left internal mammary artery. Logistic regression and Cox proportional hazards analyses were used to adjust in-hospital and medium-term outcomes, respectively. Selection bias was controlled by constructing a propensity score. A case note review was carried out to determine reasons for nonusage.

Results: A total of 4047 patients (91.8%) received the left internal mammary artery to the left anterior descending artery leaving 359 patients (8.2%) who did not. We found no difference in hospital mortality or morbidity, however, patients receiving the left internal mammary artery had a survival advantage at 4 years. Reasons for not using the left internal mammary artery were damage to the conduit (n = 44), poor flow (n = 43), poor lung function (n = 45), unstable symptoms (n = 24), vascular problems (n = 12), and 19 patients with "other" reasons (previous radiotherapy, chest wall deformity, and obese patients). Case notes had no reason stated for 146 patients and reasons for 26 patients were unobtainable.

Conclusions: Left internal mammary artery usage is not associated with any increase in hospital mortality and morbidity, but these patients have better medium-term survival. Injury on harvesting, poor flow, and poor lung function were the most common reasons for not using this conduit.