Clinical and angiographic characteristics of patients with combined anterior and inferior ST-segment elevation on the initial electrocardiogram during acute myocardial infarction

Abstract

Objective We evaluated the significance of combined anterior and inferior ST-segment elevation on the initial electrocardiogram (EKG) in patients with acute myocardial infarction (AMI) and correlated it with AMI size and left ventricular (LV) function. Methods We analyzed admission EKGs of 2996 patients with AMI from the GUSTO-I angiographic substudy and the GUSTO-IIb angioplasty substudy who underwent immediate angiography. In all, we identified 1046 patients with anterior ST elevation (ST-segment elevation in ≥2 of leads V 1-V 4) and divided them into 3 groups: Group 1, anterior + inferior ST elevation (ST elevation in ≥2 of leads II, III, aVF, n =179); Group 2, anterior ST elevation only (<2 of leads II, III, aVF with ST elevation or depression, n = 447); Group 3, anterior ST elevation + superior ST elevation (ST depression in ≥2 of leads II, III, aVF, n = 420). Results Cardiac risk factors, prior AMI, prior percutaneous transluminal coronary angioplasty or coronary artery bypass graft, Killip class, and thrombolytic therapy assignment did not differ among the 3 groups. Group 1 patients had greater number of leads with ST elevation compared to Groups 2 and 3 (ST elevation in ≥6 leads 83% vs 22% vs 49%, P = .001). Despite greater ST-segment elevation, Group 1 patients had a lower peak CK level (median baseline peak CK 1370 vs 1670 vs 2381 IU, P = .0001) and less LV dysfunction (median ejection fraction 0.53 vs 0.49 vs 0.45, P = .0001; median number of abnormal chords 21 vs 32 vs 40, P = .0001). Angiographically, Group 1 had 2 distinct subsets of patients with either right coronary artery (RCA) (59%) or left anterior descending coronary artery (LAD) (36%) occlusion. In contrast, the infarct-related artery (IRA) was almost entirely the LAD in Groups 2 and 3 (97%). Further, the site of IRA occlusion in Group 1 was mostly proximal RCA (67%) in the RCA subgroup and mid or distal LAD (70%) in the LAD subgroup. ST-segment elevation in lead V 1 ≥ V 3 and absence of progression of ST elevation from lead V 1 to V 3 on the EKG differentiated IRA-RCA from IRA-LAD in patients with combined anterior and inferior ST elevation. Conclusions The AMI size and LV dysfunction in patients with anterior ST elevation is directly related to the direction of ST segment deviation in the leads II, III, aVF; least with inferior ST elevation, intermediate with no ST deviation, and maximal with superior ST elevation (inferior ST depression). Despite greater ST-segment elevation, patients with combined anterior and inferior ST elevation have limited AMI size and preserved LV function. Angiographically, they comprise 2 distinct subsets with either proximal RCA or mid to distal LAD occlusion. A predominant right ventricular and limited inferior LV AMI from a proximal RCA occlusion, or a smaller anterior AMI from a more distal occlusion of LAD may explain their limited AMI size despite greater ST elevation.