Directional coronary atherectomy (DCA) was performed in 158 patients over a 2-year period at the Mayo Clinic. Primary atheromatous lesions were treated in 92 patients (group 1) and restenosis lesions were treated in 66 (group 2). Technical success (recovery of tissue and greater than or equal to 40% luminal enlargement with a residual stenosis of less than 50%) was achieved in 152 lesions (92%); clinical success (technical success and no in-hospital death, Q-wave myocardial infarction or coronary bypass surgery) was achieved in 143 patients (91%). Adjunctive balloon angioplasty was used in 41 patients. DCA was successful less often in group 1 than in group 2 (86 vs 97%; p = 0.038). A major complication occurred in 7% of patients; in-hospital death, Q-wave myocardial infarction and emergency coronary bypass surgery occurred in 3, 1 and 4% of patients, respectively. Major complications were more frequent in group 1 than in group 2 (10 vs 1; p = 0.02). During a follow-up period of 14 +/- 8 months, no difference between the groups was found in the incidence of late death (4%), Q-wave myocardial infarction (1%), recurrent severe angina (29%), bypass surgery (15%) or repeat interventional procedure of the same vascular segment (24%). Vein graft and restenosis lesions tended to have greater success and fewer complications. Angiographic restenosis (increase of greater than or equal to 30% in stenosis severity by visual assessment) occurred in 62% of patients and 58% of lesions with successful DCA, and was similar in the 2 groups; a tendency toward higher restenosis rates was seen in patients with vein graft DCA.(ABSTRACT TRUNCATED AT 250 WORDS)