Steal-prone coronary anatomy and myocardial ischemia associated with four primary anesthetic agents in humans. To examine the relationship between myocardial ischemia in patients with steal-prone coronary anatomy and the administration of isoflurane anesthesia, we reviewed coronary angiograms of 955 patients who had participated in a randomized trial of the use of one of four primary anesthetics for coronary artery bypass operations. Steal-prone anatomy was found in 31.8% of patients who had received enflurane; 40.0%, halothane; 32.6%, isoflurane; and 31.7%, sufentanil. Detected by greater than or equal to 0.1 mV ST segment displacement, ischemia during anesthesia occurred in 290 (30.4%) of all patients with no difference in the incidence among the four primary anesthetics (27.5%-32.9%). Patients with steal-prone anatomy did not suffer more ischemia than patients who needed coronary artery bypass surgery but with other varieties of coronary anatomy. In patients with steal-prone coronary anatomy, the incidence of myocardial ischemia by primary anesthetic was 24.0% with enflurane, 34.4% with halothane, 32.1% with isoflurane, and 38.2% with sufentanil. Systolic blood pressure less than 90 mm Hg during anesthesia occurred in 416 (45.6%) patients and was twice as common during administration of volatile anesthetics than during that of sufentanil. Hypotension did not increase ischemia frequency in patients with steal-prone anatomy with use of any of the four primary anesthetics including isoflurane. Ischemia was temporally related to hypotension in only 9 patients (0.9%). In none of the 42 patients who had steal-prone anatomy and hypotension during isoflurane anesthesia was ischemia temporally related to hypotension. 