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OMI ECG Patterns

Homepage: EMNote.org ■ 🚩Membership: https://tinyurl.com/joinemnote 🚩ACLS Lecture: https://tinyurl.com/emnoteacls OMI: Occlusion Myocardial Infarction Definition: OMI is caused by complete blockage of a coronary artery, leading to significant myocardial damage. Clinical Significance: Often presents with ST-segment elevation (STEMI) and requires urgent intervention, such as PCI, to restore blood flow. Limitations of Traditional STEMI & NSTEMI Classification The traditional STEMI/NSTEMI classification, which relies on the presence or absence of ST-segment elevation on an ECG, does not always accurately identify all cases of acute coronary occlusion. This can lead to delays in treatment for patients experiencing OMI, as some cases may be misclassified as NSTEMI, potentially delaying necessary interventions. ECG Patterns Indicative of OMI Subtle ST Elevation Subtle ST elevation, even if it doesn't meet traditional STEMI criteria, can indicate acute coronary occlusion. About 75% of initially overlooked OMI cases can be identified by subtle ST changes that suggest evolving ST-segment elevation. Wellens Syndrome Wellens syndrome is characterized by biphasic (pattern A) or deeply inverted (pattern B) T waves in leads V2-V3 without Q waves. This pattern, often seen in patients with recently resolved chest pain, indicates critical stenosis of the proximal left anterior descending (LAD) coronary artery. It represents reperfusion of an occlusion that occurred during the pain episode but was not captured on ECG. Hyperacute T Waves Hyperacute T waves are an early ECG sign of OMI and often precede ST elevation. They are broader and more symmetrical than normal T waves, with a larger area under the curve relative to their QRS complex. The ratio of T-wave amplitude to the preceding QRS complex is more clinically significant than isolated T-wave amplitude. De Winter Pattern The De Winter pattern is characterized by upward-sloping ST-depression at the J point in precordial leads (V1-V6), followed by tall, symmetrical T waves, and ST-segment elevation in lead aVR. This pattern signifies proximal LAD occlusion. Aslanger's Pattern Aslanger's pattern presents with isolated ST-segment elevation in lead III, often less than 1 mm, accompanied by widespread ST-depression. It does not meet STEMI criteria because it lacks ST elevation in a contiguous lead. This pattern is associated with inferior OMI, more commonly due to circumflex occlusion than right coronary artery (RCA) occlusion, particularly in patients with multivessel disease. South African Flag Sign The South African flag sign, a pattern indicating high lateral infarction, is characterized by ST-segment elevation in leads I, aVL, and V2, along with ST-depression in lead III. This pattern often presents with subtle ST elevation and is associated with occlusion of the first diagonal branch of the LAD. New-Onset Bifascicular Block New-onset bifascicular block, particularly right bundle branch block (RBBB), is a high-risk indicator for OMI. This is because the blood supply to the bundle branches, responsible for electrical conduction in the heart, comes from septal perforators of the proximal LAD. A new bifascicular block can suggest blockage in this artery. Posterior OMI Posterior OMI, often challenging to diagnose with a standard 12-lead ECG, can be suspected with ST-depression in leads V1-V3. Adding posterior leads (V7-V9) can confirm the diagnosis if they show ST elevation. Terminal QRS Distortion Terminal QRS distortion, defined as the absence of both an S wave and J-point notching in leads V2 and V3, is highly specific for LAD occlusion and virtually absent in early repolarization. Modified Sgarbossa-Smith Criteria Diagnosing OMI in patients with left bundle branch block or ventricular paced rhythm can be difficult due to altered ventricular depolarization and repolarization. The modified Sgarbossa-Smith criteria- provide a more sensitive and specific approach than the original Sgarbossa criteria. These criteria require: Concordant ST-segment elevation ≥ 1 mm in at least one lead. Concordant ST-depression ≥ 1 mm in any of leads V1-V3. Proportionally excessive discordant ST-segment elevation (≥ 1 mm) in at least one lead, defined as ≥ 25% of the depth of the preceding S wave (ST/S ratio ≥ 0.25). Precordial Swirl The "precordial swirl" pattern exhibits a clockwise vortex appearance of ST-T waves across precordial leads, with marked ST elevation and/or hyperacute T waves in V1-V2, and ST-depression and/or T-wave inversion in V5-V6. This pattern signifies LAD occlusion, typically proximal to the first septal perforator. Northern OMI "Northern OMI," a novel pattern observed in patients with multivessel coronary artery disease, presents with ST elevation in aVR and aVL with negative T waves and ST depression in inferior and lateral precordial leads with positive or biphasic T waves.