Five-year results of coronary bypass grafting for patients older than 70 years: role of internal mammary artery. Despite numerous references to the superiority of the internal mammary artery (IMA) over the saphenous vein for myocardial revascularization, its role in the elderly is still in question. From January 1984 through December 1988, 1,081 patients older than 70 years (mean age, 74.9 years) underwent bypass grafting, 354 (33%) receiving left IMA grafts based on the surgeon's preference and 727 (67%) receiving vein grafts only. Selection bias resulted in a higher incidence of known risk factors (such as cardiomegaly, arrhythmias, left ventricular failure, wall motion abnormalities, and preoperative combined New York Heart Association/Canadian Cardiovascular Association functional class IV) in patients in whom the IMA was not used. However, unstable angina, acute myocardial infarction, left ventricular dysfunction, and left main disease were not contraindications for using IMA grafts. The operative mortality rate was significantly lower in IMA patients (2.8% versus 7.6%). The actuarial 5-year survival rate (standard error) was higher in patients with IMA grafts, 89% (3%) versus 78% (2%), and postoperative functional class improved to a greater extent in IMA patients (87% of patients were in classes I and II). Arrhythmias and myocardial infarction were significant causes of late death only in patients with vein grafts. When patients are older than 70 years, patient selection factors clearly play an important role in the differential results between patients in whom the IMA is used and patients in whom vein grafts are used. As in younger patients, excellent results can be achieved in the elderly. 