Implications of inferior ST-segment depression in anterior acute myocardial infarction: Electrocardiographic and angiographic correlation

Abstract

This study assesses the significance of inferior ST-segment depression during anterior acute myocardial infarction (AMI) by investigating the relationship between inferior ST-segment depression and (1) the site of the left anterior descending (LAD) coronary artery lesion and (2) ST-segment deviation in the various anterior and lateral leads. We studied 126 patients with anterior AMI who underwent coronary angiography within 21 days of hospitalization. The admission 12-lead electrocardiograms were evaluated for ST-segment amplitude in each lead at 0.08 second after the J-point. Coronary angiography was evaluated for the site and severity of luminal narrowing of the coronary arteries. The site of the culprit lesion in the LAD artery, relative to the origin of the first septal and diagonal branches, was determined. In four patients no lesion was identified in the LAD artery. Of the remaining 122 patients, 40 and 53 patients had a LAD artery lesion proximal to the first septal and first diagonal branches, respectively. Additional luminal narrowing (≥70% of diameter) was found in the circumflex and the right coronary arteries in 27 and 37 patients, respectively. ST-segment depression of >1 mm in leads II, III, and aVF was noted in 24, 29, and 24 patients, respectively. The prevalence of a LAD artery preseptal and prediagonal lesion was higher in patients with inferior ST-segment depression. The positive predictive values of ST-segment depression >1 mm in leads II, III, and aVF for a lesion proximal to the first septal branch were 58.3%, 65.5%, and 75%, respectively, and those for a prediagonal lesion were 70.8%, 79.3%, and 87.5%. The corresponding specificities were 88%, 88%, and 93% for a preseptal lesion, and 90%, 91%, and 96% for a prediagonal lesion. No differences were observed between the groups with interior ST-segment depression in the distribution of single-vessel or three-vessel disease or significant right or circumflex coronary artery narrowing. Univariate linear regression models revealed that the magnitude of the ST amplitude in leads III and aVF is mainly affected by the ST amplitude in leads I and aVL (coefficient of the regression −0.75 and −0.80, R 2 = 43% and 68%, for lead III, respectively; coefficient of the regression −0.57, and −0.66, R 2 = 32% and 58%, for lead aVF, respectively). The magnitude of the ST deviation in the precordial leads has only a minor impact on the inferior ST-segment deviation. Multivariate regression models confirmed that the ST deviation in leads III and aVF is mainly influenced by the ST levels in aVL. It is concluded that ST-segment depression in the inferior leads during anterior AMI represents reciprocal changes to the high anterolateral region, shown by ST-segment elevation in leads I and aVL. ST depression in the inferior leads predicts a culprit lesion proximal to the origin of the first diagonal branch. No relationship was found between the magnitude of ST-segment depression in leads II, III, and aVF and the occurrence of right coronary or left circumflex artery narrowing or three-vessel disease.