The relationship of ST segment elevation shape with preserved myocardium and signal-averaged electrocardiography in acute anterior myocardial infarction
Although a relation between magnitude of ST segment elevation and myocardial damage has been shown in the early period of acute myocardial infarction (AMI), such a relation between the shape of the ST segment elevation, myocardial damage, and the clinical course remains obscure. For this purpose 62 first anterior AMI patients admitted in the first 6 h were enrolled for the study. On the basis of precordial V3 derivation prior to thrombolytic therapy, the shape of the ST elevation was separated into three groups: concave (n = 26), straight (n = 24), or convex types (n = 12). The relation between the shape of the ST elevation recorded on admission, and the results of predischarge low-dose dobutamine stress echocardiography (LDE) performed (n = 53) and signal-averaged ECG values were investigated. The basal wall motion score index (WMSI) and response to LDE in the concave group were better in the infarct zone. Additionally, the average akinetic segment number in the infarct zone was higher, and improvement in these segments was less in the convex and straight groups (concave 3.78 ± 2 vs 2.17 ± 2.1, P < 0.01; straight 5.15 ± 2.7 vs 4.45 ± 2.8, not significant (NS); convex 5.4 ± 2.3 vs 4.8 ± 2.1, NS; basal vs LDE). While only 13% (3/23) of the patients did not respond to LDE (P < 0.05 vs group B and P < 0.01 vs group C), 35% (7/20) of group B and 60% (6/10) of group C patients did not respond to LDE. Although no relation was found between better left ventricular function (WMSI < 2) and shape of the ST elevation in basal evaluation by multiple logistic regression analysis (P = 0.06), an independent relation was found between them following LDE (P = 0.01, odds ratio (OR) 4.5, 95% Confidence Interval (CI) 1.3–14.7). The incidence of ventricular late potential (LP) positivity was 11% (3/26) in the concave group, 16% (4/24) in the straight group, and 58% (7/12) in the convex group (P < 0.001 vs concave and P < 0.05 vs straight groups). We found that shape of the ST elevation could significantly predict the presence of late potentials in multiple logistic regression analysis (P = 0.003, OR 10.7, 95% CI 2.2–51.7). There was no in-hospital death in the concave group, whereas five patients died in either the straight or the convex group. Furthermore, arrhythmia was lower in the concave group during this period (P < 0.05), and exercise capacity was lower. In conclusion, we determined that there was a higher viable myocardium, and lower LP(positivity) and in-hospital mortality in patients with concave ST elevation on admission.