Acute Myocardial Infarct

Acute Myocardial InfarctCreated OnApril 21, 2020Last Updated OnApril 21, 2020byadmin You are here: Main ECG Acute Myocardial Infarct < All Topics Table of Contents Classic STEMI: Use the J-point to determine the magnitude of ST-segment elevation relative to the isoelectric TP segment. J-point elevation in 2 contiguous leads > 1 mm is required in all leads (except V2/V3) Leads V2and V3 limits are age and sex dependent: men < 40 years: Cut-off = ≥ 2.5 mm in V2and V3 men ≥ 40 years: Cut-off = ≥ 2 mm in V2and V3 Women: Cut-off = ≥ 1.5 mm in V2 and V3 Clinical Pearls: Lesser degrees of ST displacement DO NOT exclude ischemia or evolving MI A single ECG may miss dynamic changes, so do serial ECGs Anterior STEMI Occurs when anterior myocardial tissue usually supplied by the left anterior descending coronary artery suffers injury due to lack of blood supply. ECG manifestation: ST segment elevation + Q wave in the precordial leads (V1-6) ± the high lateral leads (I and aVL) Reciprocal ST depression in the inferior leads (mainly III and aVF) Inferior STEMI Inferior STEMI can result from occlusion of all three coronary arteries: The vast majority (~80%) of inferior STEMIs are due to occlusion of the dominant right coronary artery (RCA). Less commonly (around 18% of the time), the culprit vessel is a dominant left circumflex artery (LCx). Occasionally, inferior STEMI may result from occlusion of a “type III” or “wraparound” left anterior descending artery (LAD). This produces the unusual pattern of concomitant inferior and anterior ST elevation ECG manifestation: ST elevation in leads II, III and aVF Progressive development of Q waves in II, III and aVF Reciprocal ST depression in aVL (± lead I) Lateral STEMI The lateral wall of the LV is supplied by branches of the left anterior descending (LAD) and left circumflex (LCx) arteries Infarction of the lateral wall usually occurs as part of a larger territory infarction, e.g. anterolateral STEMI ECG manifestation: ST elevation in the lateral leads (I, aVL, V5-6) Reciprocal ST depression in the inferior leads (III and aVF) ST elevation primarily localized to leads I and aVL is referred to as a high lateral STEMI   Three broad categories of lateral infarction: Anterolateral STEMI due to LAD occlusion   ST elevation is present in the anterior (V2-4) and lateral leads (I, aVL, V5-6) Q waves are present in both the anterior and lateral leads, most prominently in V2-4 There is reciprocal ST depression in the inferior leads (III and aVF) This pattern indicates an extensive infarction involving the anterior and lateral walls of the left ventricle ST elevation in the precordial leads plus the high lateral leads (I and aVL) is strongly suggestive of an acute proximal LAD occlusion (this combination predicts a proximal LAD lesion 87% of the time) Inferior-posterior-lateral STEMI due to LCx occlusion ST elevation is present in the inferior (II, III and aVF) and lateral leads (I, V5-6) ST depression in V1-3 with tall, broad R waves and upright T waves and a R/S ratio > 1 in V2 indicate concomitant posterior infarction (this patient also had ST elevation in the posterior leads V7-9) These changes are consistent with a massive infarction involving the inferior, lateral and posterior walls of the left ventricle The culprit vessel is again very likely to be an occluded proximal circumflex artery Isolated lateral infarction due to occlusion of smaller branch arteries such as the D1, OM or ramus intermedius ST elevation is present in the high lateral leads (I and aVL) There is reciprocal ST depression in the inferior leads (III and aVF) QS waves in the anteroseptal leads (V1-4) with poor R wave progression indicate prior anteroseptal infarction This pattern suggests proximal LAD disease with an acute occlusion of the first diagonal branch (D1) Posterior STEMI The most common type...

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