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Acute anterolateral MI is recognised by ST-segment elevation in leads I, aVL and the precordial leads overlying the anterior and lateral surfaces of the heart (V3 - V6). Generally speaking, the more significant the ST elevation, the more severe the infarction. There is also a loss of general R wave progression across the precordial leads and there may be symmetric T wave inversion as well. Anterolateral myocardial infarctions frequently are caused by occlusion of the proximal left anterior descending coronary artery, or combined occlusions of the LAD together with the right coronary artery or left circumflex artery. Arrhythmias which commonly preclude the diagnosis of anterolateral MI on ECG and therefore possibly identify high-risk patients include right and left bundle branch blocks, hemiblocks and type II second degree atrioventricular conduction blocks.
Leads II, III and aVF reflect electrocardiogram changes associated with acute infarction of the inferior aspect of the heart. ST-elevation, developing Q waves and T wave inversion may all be present depending on the timing of the ECG relative to the onset of myocardial infarction. Most frequently, inferior MI results from occlusion of the right coronary artery. Conduction abnormalities that may alert the physician to patients at risk include second degree AV block and complete heart block together with junctional escape beats. Note that the patient below is also suffering from a concurrent posterior wall infarction as evidenced by ST depression in leads V1 and V2.
When examining the ECG from a patient with a suspected posterior MI, it is important to remember that because the endocardial surface of the posterior wall faces the precordial leads, changes resulting from the infarction will be reversed on the ECG. Therefore, ST segments in leads overlying the posterior region of the heart (V1 and V2) are initially horizontally depressed. As the infarction evolves, lead V1 demonstrates an R wave (which in fact represents a Q wave in reverse). Note that the patient below is also suffering from an inferior wall myocardial infarction as evidenced by ST elevation in leads II, III and aVF. />
Acute septal MI is associated with ST elevation, Q wave formation and T wave inversion in the leads overlying the septal region of the heart (V2 and V3).
ST elevation in the setting of chest pain must be treated as a medical emergency and possible STEMI
Anterior STEMI with tombestoning
Anterior STEMI with tombestoning
ST elevation, no R waves V1-V6, Pathological Q waves in III and aVF
ST elevation I, aVL, V2-V6, ST depression a VR, III, aVF. Loss of R waves, path Q waves I,aVL, V2-V4
Pathological Q waves in II, III, aVF with inverted T waves. Flattened T waves in V5=V6
Pathological Q waves in I,aVl, V2-6, Loss of R waves V2-5, T waves inverted V5-6 and flattened or inverted in II,III, avF, ST elevation V2-4
ST elevation I, II, aVF, aVL, V3-V6, Pathological Q wave in aVL