Several studies have examined the ability of electrocardiography to differentiate between takotsubo cardiomyopathy (TC) and anterior wall acute ST-segment elevation myocardial infarction (AA-STEMI). In those studies, the magnitude of ST-segment elevation was not measured at the J point. The American Heart Association, American College of Cardiology Foundation, and Heart Rhythm Society guidelines recommend that the magnitude of ST-segment elevation should be measured at the J point. Accordingly, the aim of this study was to retrospectively examine whether electrocardiography, using the magnitude of ST-segment elevation measured at the J point, could differentiate 62 patients with TC from 280 with AA-STEMI. Patients with AA-STEMI were divided into following subgroups: 140 with left anterior descending coronary artery occlusions proximal to the first diagonal branch (AA-STEMI-P), 120 with left anterior descending occlusions distal to the first diagonal branch and proximal to the second diagonal branch (AA-STEMI-M), and 20 with left anterior descending occlusions distal to the second diagonal branch (AA-STEMI-D). TC had a much lower prevalence of ST-segment elevation ≥1 mm in lead V 1 (19.4%) compared to AA-STEMI (80.4%, p <0.01), AA-STEMI-P (80.7%, p <0.01), AA-STEMI-M (80%, p <0.01), and AA-STEMI-D (80%, p <0.01). ST-segment elevation ≥1 mm in ≥1 of leads V 3 to V 5 without ST-segment elevation ≥1 mm in lead V 1 identified TC with sensitivity of 74.2% and specificity of 80.6%. Furthermore, this criterion could differentiate TC from each AA-STEMI subgroup, with similar diagnostic values. In conclusion, using the magnitude of ST-segment elevation measured at the J point, a new electrocardiographic criterion is proposed with an acceptable ability to differentiate TC from AA-STEMI.
Takotsubo cardiomyopathy (TC), which is also called transient apical ballooning and stress cardiomyopathy, is an acute cardiac syndrome characterized by transient wall motion abnormality typically involving the apical and middle portions of the left ventricle with hyperkinesia of the basal segment in the absence of significant coronary artery disease. Although TC usually develops after exposure to an acute emotional or physiologic stress in postmenopausal women, symptoms and electrocardiographic findings of TC mimic those of anterior wall acute ST-segment elevation myocardial infarction (AA-STEMI). Therefore, early diagnostic differentiation between TC and AA-STEMI is very important for determining the appropriate treatment strategy. Several studies have examined the ability of electrocardiography to differentiate between TC and AA-STEMI. However, in those studies, the magnitude of ST-segment elevation was measured at 80 ms after the J point. The American Heart Association, American College of Cardiology Foundation, and Heart Rhythm Society guidelines recommend that the magnitude of ST-segment elevation should be measured at the J point. Accordingly, we retrospectively examined whether electrocardiography, using the magnitude of ST-segment elevation measured at the J point, can differentiate TC from AA-STEMI.
Methods
Sixty-two patients with TC (6 men and 56 women, mean age 74.5 ± 10.4 years) and 280 patients with AA-STEMI (212 men and 68 women, mean age 62.4 ± 10.9 years) were retrospectively enrolled in this study. The inclusion criteria were hospital admission <6 hours after the onset of symptoms, followed by emergency coronary angiography; no previous myocardial infarction; no electrocardiographic findings such as bundle branch block, intraventricular conduction disturbance, or ventricular rhythm; and no other heart or lung disease affecting the electrocardiographic findings. TC was defined as transient akinesia or dyskinesia of the left ventricular apical and midventricular segments with regional wall motion abnormalities extending to the epicardial coronary artery; coronary angiography documenting the absence of obstructive (>50% luminal stenosis) epicardial coronary artery; new electrocardiographic abnormalities; and the absence of recent significant head trauma, intracranial bleeding, suspected pheochromocytoma, myocarditis, or hypertrophic cardiomyopathy. AA-STEMI was defined as typical ischemic chest pain lasting ≥20 minutes; significant J-point 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 electrocardiography ; an increase in the serum creatine kinase level ≥2 times the normal value; and identification of the infarct-related lesion in the left anterior descending coronary artery (LAD) by emergency coronary angiography.
A standard 12-lead electrocardiogram was obtained in all patients at the time of hospital presentation and was recorded at a paper speed of 25 mm/s and an amplification of 10 mm = 1 mV. The magnitude of ST-segment level in each lead was measured at the J point. We analyzed the following electrocardiographic findings: the presence or absence of ST-segment elevation ≥1 mm in each limb (displayed by the orderly sequence) and precordial lead and the presence or absence of reciprocal ST-segment depression in the inferior leads. Reciprocal ST-segment depression was defined as horizontal or downsloping ST-segment depression ≥1 mm in ≥2 of leads II, III, and aVF. The determination of electrocardiographic findings was made by the consensus of 2 observers, who were blinded to all patients’ clinical and angiographic data.
Emergency coronary angiography and left ventriculography were performed by the radial, brachial, or femoral approach. Images of the coronary arteries were obtained in multiple views. Left ventriculography was performed in the 30° right anterior oblique projection. The determination of the site of LAD occlusion was made by the consensus of 2 observers, who were blinded to all patients’ clinical and electrocardiographic data.
Continuous data are expressed as mean ± SD. Comparisons of continuous data were performed using the unpaired Student’s t test or the Mann-Whitney U test. Categorical data were analyzed using the Fisher’s exact test or the chi-square test. 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
Patient characteristics are listed in Table 1 . Patients with TC were significantly older and had significantly lower body mass indexes than those with AA-STEMI. The prevalences of male gender, diabetes mellitus, dyslipidemia, and smoking history were significantly lower in patients with TC than in those with AA-STEMI.
| Variable | TC | AA-STEMI |
|---|---|---|
| (n = 62) | (n = 280) | |
| Age (years) | 74.5 ± 10.4 | 62.4 ± 10.9 ⁎ |
| Men | 9.7% | 75.7% ⁎ |
| Body mass index (kg/m 2 ) | 20.4 ± 3.4 | 23.3 ± 3.7 ⁎ |
| Hypertension | 41.9% | 52.1% |
| Dyslipidemia | 24.2% | 51.8% ⁎ |
| Diabetes mellitus | 12.9% | 26.4% † |
| Smokers | 12.9% | 66.4% ⁎ |
| Time to admission (minutes) | 171.1 ± 106.1 | 144.0 ± 78.7 |
Patients with AA-STEMI were divided into 3 subgroups according to the site of LAD occlusion: 140 with LAD occlusions proximal to the first diagonal branch (AA-STEMI-P), 120 with LAD occlusions distal to the first diagonal branch and proximal to the second diagonal branch (AA-STEMI-M), and 20 with LAD occlusions distal to the second diagonal branch (AA-STEMI-D). Table 2 lists comparisons of electrocardiographic findings between TC and AA-STEMI or each AA-STEMI subgroup. The prevalences of ST-segment elevation ≥1 mm in leads V 1 , V 2 , and V 6 differed significantly between TC and AA-STEMI or each AA-STEMI subgroup. In particular, the differences in the prevalence of ST-segment elevation ≥1 mm in lead V 1 were extremely great between TC and AA-STEMI or each AA-STEMI subgroup.
| Variable | TC | AA-STEMI | AA-STEMI-P | AA-STEMI-M | AA-STEMI-D |
|---|---|---|---|---|---|
| (n = 62) | (n = 280) | (n = 140) | (n = 120) | (n = 20) | |
| ST-segment elevation ≥1 mm | |||||
| Lead aVL | 4.8% | 38.6% ⁎ | 50.7% ⁎ | 30% ⁎ | 5% |
| Lead I | 12.9% | 23.6% | 29.3% † | 19.2% | 10% |
| Lead −aVR | 16.1% | 3.9% ⁎ | 5.7% † | 2.5% ⁎ | 10% |
| Lead II | 22.6% | 2.5% ⁎ | 1.4% ⁎ | 2.5% ⁎ | 10% |
| Lead aVF | 14.5% | 1.4% ⁎ | 0.7% ⁎ | 1.7% ⁎ | 10% |
| Lead III | 9.7% | 1.8% ⁎ | 0% ⁎ | 2.5% | 10% |
| Lead V 1 | 19.4% | 80.4% ⁎ | 80.7% ⁎ | 80% ⁎ | 80% ⁎ |
| Lead V 2 | 67.7% | 97.9% ⁎ | 98.6% ⁎ | 97.5% ⁎ | 95% † |
| Lead V 3 | 87.1% | 98.9% ⁎ | 99.3% ⁎ | 98.3% ⁎ | 100% |
| Lead V 4 | 82.3% | 88.2% | 86.4% | 90.8% | 85% |
| Lead V 5 | 64.5% | 63.2% | 59.3% | 69.2% | 55% |
| Lead V 6 | 51.6% | 31.8% ⁎ | 34.3% † | 30% ⁎ | 25% † |
| Reciprocal ST-segment depression in the inferior leads | 6.5% | 58.6% ⁎ | 72.9% ⁎ | 49.2% ⁎ | 15% |
Tables 3 and 4 list the prevalences of combined electrocardiographic findings, including the absence of ST-segment elevation ≥1 mm in lead V 1 , in TC, AA-STEMI, and each AA-STEMI subgroup and the diagnostic values of those electrocardiographic findings for differentiating TC from AA-STEMI or each AA-STEMI subgroup, respectively. ST-segment elevation ≥1 mm in ≥1 of leads V 3 to V 5 without ST-segment elevation ≥1 mm in lead V 1 had a sensitivity of 74.2% and a specificity of 80.6% for differentiating TC from AA-STEMI. This electrocardiographic finding had specificities of 80.7%, 80%, and 80% for differentiating TC from AA-STEMI-P, AA-STEMI-M, and AA-STEMI-D, respectively.
| Variable | TC | AA-STEMI | AA-STEMI-P | AA-STEMI-M | AA-STEMI-D |
|---|---|---|---|---|---|
| (n = 62) | (n = 280) | (n = 140) | (n = 120) | (n = 20) | |
| ST-segment elevation ≥1 mm in lead V 3 without ST-segment elevation ≥1 mm in lead V 1 | 67.7% | 19.3% ⁎ | 19.3% ⁎ | 19.2% ⁎ | 20% ⁎ |
| ST-segment elevation ≥1 mm in lead V 3 and/or V 4 without ST-segment elevation ≥1 mm in lead V 1 | 72.6% | 19.6% ⁎ | 19.3% ⁎ | 20% ⁎ | 20% ⁎ |
| ST-segment elevation ≥1 mm in ≥1 of leads V 3 to V 5 without ST-segment elevation ≥1 mm in lead V 1 | 74.2% | 19.6% ⁎ | 19.3% ⁎ | 20% ⁎ | 20% ⁎ |
| ST-segment elevation ≥1 mm in ≥2 contiguous precordial leads without ST-segment elevation ≥1 mm in lead V 1 | 69.4% | 19.6% ⁎ | 19.3% ⁎ | 20% ⁎ | 20% ⁎ |
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