New electrocardiographic criteria for posterior wall acute myocardial ischemia validated by a percutaneous transluminal coronary angioplasty model of acute myocardial infarction

The standard 12-lead electrocardiogram (ECG) fails to detect ST-segment elevation in patients with posterior wall acute myocardial ischemia. However, additional posterior leads V7-9 provide limited additional diagnostic information to the standard 12-lead ECG when an ischemic criterion of 1-mm ST elevation is used. No study is available to delineate the ischemic criteria in the posterior electrocardiographic leads. Continuous 15-lead ECGs (standard 12 lead + V7-9) were recorded in 53 subjects undergoing elective left circumflex coronary angioplasty (posterior ischemia model), ST amplitudes (J + 60 ms) at preangioplasty baseline were subtracted from maximal ST amplitudes during balloon occlusion to create a positive or negative change score (Delta ST) for each of the 15 leads, During 53 left circumflex occlusions, 26 subjects (49%) had Delta ST elevation of greater than or equal to1 mm and 24 subjects (45%) had Delta ST elevation ranging from 0.5 to 0.95 mm in greater than or equal to1 posterior leads, Five subjects (9%) had Delta ST elevation of greater than or equal to1 mm in the posterior leads without ST elevation anywhere in any of the 12 leads, The sensitivity in detecting myocardial ischemia using 15-lead ECGs (58%) was not statistically different from the standard 12-lead ECG (49%) (p = 0.06), Adjusting the ischemic criterion from 1 to 0.5 mm in V7-9 significantly improved the sensitivity from 49% in the 12-lead ECG to 94% in the 15-lead ECG (p = 0.000), In addition, 12 subjects (23%) had posterior ST-segment elevation without anterior ST-segment depression. Thus, posterior leads V7-9 contribute significant additional diagnostic information above and beyond the standard 12-lead ECG only when a new ischemic criterion of 0.5 mm instead of 1 mm ST elevation is applied to the posterior leads. (C) 2001 by Excerpta Medica, Inc.