Abstract
IntroductionAcute anterior myocardial infarctions caused by proximal left anterior descending (LAD) artery occlusions are associated with a higher morbidity and mortality. Early identification of high-risk patients via the 12-lead electrocardiogram (ECG) could assist physicians and emergency response teams in providing early and aggressive care for patients with anterior ST-elevation myocardial infarctions (STEMI). Approximately 25% of US hospitals have primary percutaneous coronary intervention (PCI) capability for the treatment of acute myocardial infarctions. Given the paucity of hospitals capable of PCI, early identification of more severe myocardial infarction may prompt emergency medical service routing of these patients to PCI-capable hospitals. We sought to determine if the 12 lead ECG is capable of predicting proximal LAD artery occlusions.MethodsIn a retrospective, post-hoc analysis of the Pre-Hospital Administration of Thrombolytic Therapy with Urgent Culprit Artery Revascularization pilot trial, we compared the ECG findings of proximal and nonproximal LAD occlusions for patients who had undergone an ECG within 180 minutes of symptom onset.ResultsIn this study, 72 patients had anterior STEMIs, with ECGs performed within 180 minutes of symptom onset. In patients who had undergone ECGs within 60 minutes (n = 35), the mean sum of ST elevation (STE) in leads V1 through V6 plus ST depression (STD) in leads II, III, and aVF was 19.2 mm for proximal LAD occlusions and 11.7 mm for nonproximal LAD occlusions (P = 0.007). A sum STE in V1 through V6 plus STD in II, III, and aVF of at least 17.5 mm had a sensitivity of 52.3%, specificity of 92.9%, positive predictive value of 91.7%, and negative predictive value of 56.5% for proximal LAD occlusions. When the ECG was performed more than 60 minutes after symptom onset (n = 37), there was no significant difference in ST-segment deviation between the 2 groups.ConclusionThe sum STE (V1-V6) and STD (II, III, aVF) on a 12-lead ECG can be used to predict proximal LAD occlusions if performed within the first hour of symptom onset. This should be considered a high-risk finding and may prompt prehospital direction of such patients to PCI-capable hospitals.
Highlights
Acute anterior myocardial infarctions caused by proximal left anterior descending (LAD) artery occlusions are associated with a higher morbidity and mortality
A sum ST elevation (STE) in V1 through V6 plus ST depression (STD) in II, III, and aVF of at least 17.5 mm had a sensitivity of 52.3%, specificity of 92.9%, positive predictive value of 91.7%, and negative predictive value of 56.5% for proximal LAD occlusions
A significant difference in sum STE and ST depression does not exist when comparing all data within 180 minutes of symptom onset or when comparing ECGs performed within 61 to180 minutes from symptom onset
Summary
Acute anterior myocardial infarctions caused by proximal left anterior descending (LAD) artery occlusions are associated with a higher morbidity and mortality. Acute ST-elevation myocardial infarctions (STEMI) due to occlusion of the left anterior descending (LAD) artery have a poorer prognosis than right coronary artery and left circumflex artery occlusions.. Proximal LAD occlusions are associated with a higher 30-day mortality and 3-year mortality than distal LAD occlusions in acute anterior myocardial infarctions.. Proximal LAD occlusions are associated with a higher 30-day mortality and 3-year mortality than distal LAD occlusions in acute anterior myocardial infarctions.2,6,7 Identification of this highest-risk subgroup with the 12-lead electrocardiogram (ECG) will allow healthcare providers to rapidly assess the potential severity of the STEMI. During an STEMI, the natural progression of ECG findings is as follows: [1] hyperacute T waves, [2] ST-segment elevation, [3] pathologic Q waves, and [4] T-wave inversion with ST-segment resolution. Extensive anterior myocardial infarctions have a steady decrease in sum ST elevation (STE) over the first 3 hours, whereas antero-septal myocardial infarctions have a fairly constant sum STE over the first 3 hours. A study using dogs as a model for myocardial infarctions found that maximum STE occurred within 5 to 10 minutes of complete occlusion of the left circumflex artery.
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