Previous studies have shown that the analysis of ST-segment deviation in lead aVR on admission provides useful information on angiographic coronary anatomy and risk stratification in acute coronary syndromes. However, the association between ST-segment deviation in lead aVR on admission and left ventricular (LV) function has not been fully investigated in anterior wall acute ST-segment elevation myocardial infarction. In this study, 237 patients with first anterior wall acute ST-segment elevation myocardial infarction were examined. The patients were divided into the following 3 groups according to ST-segment deviation in lead aVR on admission: 85 with ST-segment elevation ≥0.5 mm (group A), 106 without ST-segment deviation (group B), and 46 with ST-segment depression ≥0.5 mm (group C). LV ejection fractions at predischarge were compared among the 3 groups. Among the 3 groups, there were significant differences in the prevalences of proximal left anterior descending coronary artery (LAD) occlusion (group A 75.3%, group B 56.6%, group C 45.7%, p = 0.002), long LAD (group A 27.1%, group B 31.1%, group C 56.5%, p = 0.002), and good collaterals to the LAD (group A 40.0%, group B 25.4%, group C 17.4%, p = 0.01). LV ejection fractions at predischarge did not differ among the 3 groups (group A 56.4 ± 12.5%, group B 56.9 ± 12.7%, group C 53.3 ± 12.2%, p = 0.26). On a multiple regression analysis, establishment of Thrombolysis In Myocardial Infarction grade 3 flow, proximal LAD occlusion, and long LAD were associated with the LV ejection fraction at predischarge. In conclusion, ST-segment deviation in lead aVR on admission is not associated with LV function at predischarge in first anterior wall acute ST-segment elevation myocardial infarction.
Electrocardiography is the most important initial clinical test for diagnosing acute myocardial infarction. Although lead aVR has long been neglected in the diagnosis of acute myocardial infarction, recent investigations have shown that the analysis of ST-segment deviation in lead aVR provides useful information on the angiographic anatomy of the infarct-related coronary artery and risk stratification in various conditions of acute coronary syndromes. Little information is available, however, on the association between ST-segment deviation in lead aVR on admission and left ventricular (LV) function in anterior wall acute ST-segment elevation myocardial infarction (AA-STEMI). Kosuge et al reported that in AA-STEMI, patients with ST-segment depression ≥0.5 mm in lead aVR on admission have larger infarct sizes assessed by peak creatine kinase level and more depressed LV function at predischarge than those without ST-segment depression ≥0.5 mm in lead aVR. We recently demonstrated that in AA-STEMI, ST-segment depression ≥0.5 mm in lead aVR on admission is associated with distal left anterior descending coronary artery (LAD) occlusion and long LAD and that ST-segment elevation ≥0.5 mm in lead aVR on admission is associated with proximal LAD occlusion and nonlong LAD. Considering the results of our previous study, we hypothesized that ST-segment elevation or depression in lead aVR on admission may not be associated with a large infarct size in AA-STEMI. To test this hypothesis, we examined the association between ST-segment deviation in lead aVR on admission and LV function at predischarge in patients with AA-STEMI.
Methods
From January 2000 to December 2006, 328 patients with first anterior wall acute myocardial infarctions were admitted to Almeida Memorial Hospital and Oita University Hospital within 6 hours of the onset of symptoms. A total of 237 patients (185 men and 52 women, mean age 62 ± 10 years) who met the following inclusion criteria were enrolled in this study: (1) typical ischemic chest pain lasting ≥20 minutes; (2) ST-segment elevation (defined as ST-segment elevation ≥2 mm in leads V 2 and V 3 in men aged ≥40 years, ST-segment elevation ≥2.5 mm in leads V 2 and V 3 in men aged <40 years, ST-segment elevation ≥1.5 mm in leads V 2 and V 3 in women, and ST-segment elevation ≥1 mm in other precordial leads) in ≥2 contiguous precordial leads on admission ; (3) emergency coronary angiography <1 hour after hospital admission and predischarge coronary angiography together with left ventriculography; (4) the presence of a luminal diameter stenosis of >50% in the left main trunk; (5) no previous myocardial infarction; (6) no electrocardiographic findings such as bundle branch block, intraventricular conduction disturbance, or ventricular rhythm; (7) no other heart or lung disease affecting the electrocardiographic findings; and (8) an increase in serum creatine kinase level of ≥2 times the normal value.
Standard 12-lead electrocardiograms were recorded at a paper speed of 25 mm/s and a standardization of 10 mm = 1 mV. The magnitude of ST-segment levels relative to the TP segment was measured at the J point. ST-segment elevation ≥0.5 mm in lead aVR and horizontal or downsloping ST-segment depression ≥0.5 mm in lead aVR were considered significant. The electrocardiograms were analyzed by 2 observers, who were blinded to all patients’ clinical and angiographic data.
Coronary angiography and left ventriculography at predischarge were performed about 14 days after hospital admission. Images of the coronary arteries were obtained in multiple views. Multivessel disease was defined as the presence of a luminal diameter stenosis >50% in ≥2 major coronary arteries. The coronary flow in the LAD was graded according to the classification used in the Thrombolysis In Myocardial Infarction (TIMI) trial. The grade of collateral filling to the LAD was determined by the classification of Rentrop et al. A collateral circulation with a grade of 2 or 3 was defined as “good.” A proximal LAD occlusion was defined as an occlusion of the LAD proximal to the first septal branch. The length of the LAD was evaluated using left coronary angiography obtained in the 30° right anterior oblique view, and the long LAD was defined as the one that wrapped around the apex and that perfused ≥1/4 of the inferior wall. The coronary angiograms were analyzed by 2 observers, who were blinded to all patients’ clinical data. The left ventriculogram obtained in the 30° right anterior oblique projection was analyzed for the LV ejection fraction (LVEF) and LV volumes using the area-length method.
Continuous data are expressed as mean ± SD. One-factor analysis of variance was used for comparisons of continuous data among the 3 groups. Categorical data were analyzed using the Fisher’s exact test or the chi-square test. Univariate and multiple regression analyses were performed to determine explanatory variables associated with the LVEF at predischarge. The explanatory variables used in the analyses were age, male gender, time to admission, ST-segment elevation ≥0.5 mm in lead aVR on admission, ST-segment depression ≥0.5 mm in lead aVR on admission, TIMI grade 3 flow on initial coronary angiography, proximal LAD occlusion, long LAD, multivessel disease, good collaterals to the LAD, establishment of TIMI grade 3 flow, TIMI grade 3 flow at predischarge, β-blocker use, and angiotensin-converting enzyme inhibitor and/or angiotensin receptor blocker use. A stepwise multiple regression analysis was performed using explanatory variables with p values <0.3 on univariate analyses. A p value <0.05 was considered statistically significant. All analyses were performed using SPSS version 12.0J for Windows (SPSS, Inc., Chicago, Illinois).
Results
The 237 patients were classified into the following 3 groups on the basis of ST-segment deviation in lead aVR on admission: 85 with ST-segment elevation ≥0.5 mm in lead aVR (group A), 106 without significant ST-segment deviation (group B), and 46 with ST-segment depression ≥0.5 mm in lead aVR (group C). Figure 1 shows representative electrocardiograms obtained from patients from each group. The patient characteristics are listed in Table 1 . Smoking history differed significantly among the 3 groups. Age, gender, time elapsed from onset of symptoms to admission, and the prevalences of hypertension and diabetes mellitus did not differ significantly among the 3 groups.
| Variable | Group A ⁎ | Group B † | Group C ‡ | p Value |
|---|---|---|---|---|
| (n = 85) | (n = 106) | (n = 46) | ||
| Age (years) | 64 ± 10 | 61 ± 11 | 61 ± 9 | 0.12 |
| Men | 76.5% | 80.2% | 76.1% | 0.78 |
| Time to admission (minutes) | 142.0 ± 77.5 | 140.6 ± 71.9 | 161.2 ± 80.4 | 0.27 |
| Hypertension | 57.6% | 46.2% | 41.3% | 0.14 |
| Diabetes mellitus | 20.0% | 26.4% | 32.6% | 0.27 |
| Smoking history | 64.7% | 77.4% | 58.7% | 0.04 |
⁎ Patients with ST-segment elevation ≥0.5 mm in lead aVR on admission.
† Patients without ST-segment deviation in lead aVR on admission.
‡ Patients with ST-segment depression ≥0.5 mm in lead aVR on admission.
Table 2 lists admission and predischarge coronary angiographic findings. Among the 3 groups, there were significant differences in the prevalences of proximal LAD occlusion (group A 75.3%, group B 56.6%, group C 45.7%, p = 0.002), long LAD (group A 27.1%, group B 31.1%, group C 56.5%, p = 0.002), and good collaterals to the LAD (group A 40.0%, group B 25.4%, group C 17.4%, p = 0.01). There were no significant differences in the prevalences of TIMI grade 3 flow on initial coronary angiography, multivessel disease, emergency percutaneous coronary intervention, establishment of TIMI grade 3 flow, and TIMI grade 3 flow on predischarge coronary angiography among the 3 groups.
| Variable | Group A ⁎ | Group B † | Group C ‡ | p Value |
|---|---|---|---|---|
| (n = 85) | (n = 106) | (n = 46) | ||
| Admission coronary angiography | ||||
| Multivessel disease | 34.1% | 27.4% | 21.7% | 0.30 |
| TIMI grade 3 flow | 5.9% | 5.7% | 6.5% | 0.98 |
| Proximal LAD occlusion | 75.3% | 56.6% § | 45.7% § | 0.002 |
| Good collaterals to LAD | 40.0% | 25.4% ∥ | 17.4% § | 0.01 |
| Long LAD | 27.1% ¶ | 31.1% ¶ | 56.5% | 0.002 |
| Emergency percutaneous coronary intervention | 92.9% | 94.3% | 95.7% | 0.81 |
| Establishment of TIMI grade 3 flow | 84.7% | 79.2% | 84.8% | 0.44 |
| Predischarge coronary angiography | ||||
| TIMI grade 3 flow | 90.6% | 91.5% | 91.3% | 0.98 |
⁎ Patients with ST-segment elevation ≥0.5 mm in lead aVR on admission.
† Patients without ST-segment deviation in lead aVR on admission.
‡ Patients with ST-segment depression ≥0.5 mm in lead aVR on admission.
Figure 2 shows LVEFs at predischarge. LVEFs at predischarge did not differ among the 3 groups (group A 56.4 ± 12.5%, group B 56.9 ± 12.7%, group C 53.3 ± 12.2%, p = 0.26). The prevalence of an LVEF <45% did not differ significantly among the 3 groups (group A 18.8%, group B 17.9%, group C 21.7%, p = 0.86). LV end-diastolic and end-systolic volumes did not differ significantly among the 3 groups (LV end-diastolic volume: group A 136.8 ± 43.1 ml, group B 138.5 ± 43.0 ml, group C 144.6 ± 49.1 ml, p = 0.68; LV end-systolic volume: group A 59.9 ± 28.2 ml, group B 61.5 ± 31.0 ml, group C 70.1 ± 34.7 ml, p = 0.34).
Tables 3 and 4 list the results of univariate and multiple regression analyses performed to determine explanatory variables associated with the LVEF at predischarge. A stepwise multiple regression analysis showed that the establishment of TIMI grade 3 flow, proximal LAD occlusion, and long LAD were independently associated with the LVEF at predischarge.
