Ellis JE, Shah MN, Briller JE, Roizen MF, Aronson S, Feinstein SB. A comparison of methods for the detection of myocardial ischemia during noncardiac surgery: automated ST-segment analysis systems, electrocardiography, and transesophageal echocardiography. Anesth Analg. 1992 Nov; 75(5):764-72.