Electrocardiographic changes of ST-elevation myocardial infarction in patients with complete occlusion of the left main trunk without collateral circulation: Differential diagnosis and clinical considerations☆
Introduction
Usually, acute coronary syndrome (ACS) due to involvement of the left main trunk (LMT), as a culprit artery, presents with either subtotal occlusion or total occlusion with good collateral circulation (CC). The electrocardiogram (ECG) shows non–ST-elevation myocardial infarction (NSTEMI) pattern with 7 or more leads with ST depression and a reciprocal ST elevation in aVR and often in V1.1., 2., 3. When occlusion is total and occurs with transmural involvement, without CC, it corresponds to the clinical syndrome ST-elevation myocardial infarction (STEMI) and shows a corresponding pattern in the ECG. Unfortunately, these patients usually die before reaching the hospital. The ECG changes in LMT involvement may be misinterpreted because an NSTEMI-ECG pattern is expected, consisting of predominant. Currently, some patients with total occlusion of LMT arrive alive to the hospital. These patients may present STEMI pattern with typical clinical ECG characteristics: (a) very frequent cardiogenic shock/cardiac arrest and (b) the ECG pattern described in proximal left anterior descending coronary artery (LAD) occlusion to first septal (S1) and first diagonal (D1) but without ST elevation in aVR and V1 due to left circumflex coronary artery compromise, plus very often right bundle-branch block (RBBB) and left anterior hemiblock (LAH). So far, only few case reports of LMT occlusion presenting as STEMI have been described.1., 4., 5., 6. True incidence is unknown because in these publications,1., 4., 7., 8. ACS with LMT subtotal occlusion (thrombolysis in myocardial infarction [TIMI] flow ≥ 1) or total occlusion with CC is not distinguished from total occlusion with transmural involvement and no CC (TIMI flow = 0). In this study, 7 patients with total LMT occlusion without CC evident on coronary angiography, showing a STEMI pattern in the ECG, are described.
Section snippets
Methods
From January 2008 to December 2010, 7 patients (6 men and 1 woman), representing 2% of all ACS cases in which a percutaneous coronary intervention (PCI) was performed, were included in the study. They presented with total occlusion of the LMT and a STEMI pattern in the ECG. No other artery with significant stenosis was present. Exclusion criteria were left bundle-branch block, previous myocardial infarction and cardiac surgery, and lack of ECG recording close to the time of PCI.
Results
The ECG characteristics of ST elevation in the study group are shown in Fig. 1, and a complete case (number 7), in Fig. 2. Additional data regarding the ECG, demographic, clinical, and management parameters are shown in Table. Aspirin was given to all patients before arriving to hospital. The patients were treated according to the European Society of Cardiology guidelines9; all patients were in sinus rhythm. Four patients (60%) presented RBBB plus LAH. Patient number 6 presented spontaneous
Discussion
The LMT as the culprit artery in ACS presents in most of the cases subtotal occlusion of the artery. Acute complete occlusion rapidly triggers cardiogenic shock and ventricular fibrillation, and the patient usually dies before reaching the emergency department. However, new treatments and logistic systems of care have enabled prompt arrival to the emergency department, and consequently, more patients with complete occlusion of the LMT are seen in clinical practice. Nevertheless, in-hospital
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Conflict of Interest: All authors have no conflicts of interest for this study.