Figure 27-11 Electrocardiographic (ECG) criteria for myocardial ischemia consist of 1 mm or more of J-point depression with downsloping or horizontal ST segments; slowly upsloping ST-segment depression, defined as 2 mm of ST depression measured 80 milliseconds from the J point; and ST-segment elevation. Whereas ST-segment depression indicates nontransmural ischemia, ST-segment elevation often connotes more severe degrees of ischemia reflecting transmural injury. The structure of the ST-segment slope is predictive of the severity of coronary disease shown angiographically, with downsloping ST depression indicating severe two- and three-vessel coronary artery disease more often than either horizontal or slowly upsloping ST depression does and ST-segment elevation indicating high-grade, usually proximal arterial obstruction in patients without previous myocardial infarction. (Reproduced with permission from Goldschlager N: Use of the treadmill test in the diagnosis of coronary artery disease in patients with chest pain. Ann Intern Med 97:383, 1982.)