Use of the internal mammary artery graft in Northern New England. Northern New England Cardiovascular Disease Study Group.

BACKGROUND

There is evidence that patients who receive an internal mammary artery graft (IMA) during coronary artery bypass surgery have increased long-term survival. However, an IMA is not used in all patients.

METHODS AND RESULTS

We studied the use of IMA grafts among 7944 patients undergoing initial, isolated coronary artery bypass surgery in Maine, New Hampshire, and Vermont from 1992 to 1995. Overall, the IMA graft was used in 82% of patients; of these, 97.2% had left IMA grafts. The use of the IMA graft varied considerably by patient and disease factors. Women received an IMA graft significantly less often (76% versus 85% in men, P<.01). Older patients (> or =75 years) were less likely to receive an IMA graft (67% versus 86%, P<.001). Smaller BSA was also associated with lower rates of IMA grafts in both sexes; however, men and women with BSA <1.8 m2 received an IMA graft at about the same rate. In general, more sick and more urgent patients had lower rates of IMA use. Patients with left ventricular ejection fraction <40% received an IMA less often than those with an ejection fraction > or =60% (77% versus 85%, P<.01). Patients with a greater number of diseased coronary vessels received an IMA more often (one, 78%; two, 82%; three, 85%). IMA use varied significantly by priority of surgery, with elective patients receiving an IMA 88% of the time, urgent 83%, and emergent 51% (Ptrend<.01). The use of the IMA graft varied from 42% to 95% among individual surgeons. Surgeons were consistent in their patterns of IMA graft use for specific risk groups. All surgeons had lower rates of IMA use among older patients, lower rates of IMA among women, and lower rates of IMA use among emergent or urgent patients. However, "low-use" surgeons had consistently lower rates of use within these patient groups. The overall rate of IMA graft use increased from 76% in 1992 to 86% in 1995 (Ptrend<.001). IMA graft use increased in all five centers and in all patient subgroups. The largest increases in use were seen among women (from 69% to 83%), among patients older than 75 years (from 55% to 75%), and in emergent patients (from 40% to 72%).

CONCLUSIONS

This regional prospective study of IMA graft use in initial coronary artery bypass surgery describes substantial variability in patient groups receiving an IMA as well as increasing IMA graft use over time. It also suggests that the practice patterns of surgeons are an important determinant of IMA use. These data indicate that even more patients could benefit from the use of this technique.