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ECG interpretation: NSTEMI
The document discusses the interpretation of ECG patterns in non-ST elevation myocardial infarction (NSTEMI) and emphasizes the importance of recognizing these patterns for accurate diagnosis. Key ECG changes include persistent or transient ST-segment depression and T-wave inversions, with an emphasis on avoiding misdiagnosis in difficult ECG scenarios. The document also notes the relevance of cardiac biomarkers in conjunction with ECG findings to confirm NSTEMI.
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ECG interpretation: NSTEMI
- 1. ECG interpretation: NSTEMI PrimaryPCI and direct admission of high risk NSTEMI Joanne Simpson Golden Jubilee National Hospital Wednesday 17th February 2016
- 2. Aims Recognise theECG patterns which occur in NSTEMI Focus on those which occur most commonly Difficult ECG scenarios
- 3. NSTEMI definition ST elevationmyocardial infarction (STEMI) acute chest pain and persistent ST elevation generally reflects an acute total coronary occlusion immediate reperfusion by primary angioplasty Non ST elevation myocardial infarction (NSTEMI) acute chest pain with or without ECG changes partial occlusion of a coronary artery
- 4. Myocardial Infarction NSTE-ACS Final Dx CardiacBiomarker ECG Working Dx Presentation Ischemic Discomfort ACS No ST Elevation NQMI STEMINSTEMIUA Unstable Angina QwMI ST Elevation Noncardiac Etiologies * * NSTEMI definition
- 5. Assessment of apatient with suspected ACS
- 6. NSTEMI: considerations Clinical spectrum Symptom free Ongoing ischaemia Haemodynamic instability Cardiac arrest •Ongoing pain • Marked ST depression • Heart failure • Electrical or haemodynamic instability
- 7. NSTEMI: ECG changes persistent or transient ST-segment depression T-wave inversion flat T waves or pseudo-normalization of T waves normal ECG
- 8. 1. What doesthis ECG show?
- 9. 1. What doesthis ECG show? 1. T wave flattening inferiorly 2. Normal ECG 3. T wave inversion 4. ST depression
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- 11. 2. What doesthis ECG show?
- 12. 2. What doesthis ECG show? 1. Normal ECG 2. T wave inversion 3. ST elevation 4. ST depression
- 13. 3. What doesthis ECG show?
- 14. 3. What doesthis ECG show? 1. Normal ECG 2. T wave inversion 3. ST elevation 4. ST depression
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- 16. Wellen’s syndrome Twaves: deeply inverted or biphasic Critical stenosis of left anterior descending artery Patients are high risk
- 17. Difficult ECGs Mimicsare common Aim remains not to miss STEMI or high risk NSTEMI Low threshold for discussion
- 18. 1. What doesthis ECG show?
- 19. 1. What doesthis ECG show? ST elevation anteriorly ST depression Left bundle branch block Long QT interval
- 20. 2. What doesthis ECG show?
- 21. 2. What doesthis ECG show? Left ventricular hypertrophy Anterior ST elevation ST depression Normal ECG
- 22. 3. What doesthis ECG show?
- 23. ST depression Anterior ST elevation Left ventricular hypertrophy Broad QRS complex 3. What does this ECG show?
- 24. Electrolyte abnormality Potassium,sodium, calcium and magnesium all essential for normal electrical activity of heart Characteristic ECG changes but many are non specific Consider in: - underlying kidney disease - vomiting, diarrhoea and dehydration
- 25. Summary The clinicalpresentation is paramount ECG changes in combination with positive troponin highly suggestive of NSTEMI Be aware of mimics
- 26. Extra ECGs ifhave time
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- 32. Right bundle branchblock
Editor's Notes
- #4 Mainstay of treatment
- #8 One third of patients have normal ECG Dynamic process – changes in seconds/minutes/hours - repeat ECGs are useful Bundle branch block or paced rhythms are of no value in diagnosis of NSTEMI Discussion for comparison with old ECGs is very helpful- are changes new /old
- #9 ST depression due to subendocardial ischaemia is usually widespread — typically present in leads I, II, V4-6 and a variable number of additional leads. A pattern of widespread ST depression plus ST elevation in aVR > 1 mm is suggestive of left main coronary artery occlusion. ST depression localised to a particular territory (esp. inferior or high lateral leads only) is more likely to represent reciprocal change due to STEMI. The corresponding ST elevation may be subtle and difficult to see, but should be sought.
- #10 ST depression due to subendocardial ischaemia is usually widespread — typically present in leads I, II, V4-6 and a variable number of additional leads. A pattern of widespread ST depression plus ST elevation in aVR > 1 mm is suggestive of left main coronary artery occlusion. ST depression localised to a particular territory (esp. inferior or high lateral leads only) is more likely to represent reciprocal change due to STEMI. The corresponding ST elevation may be subtle and difficult to see, but should be sought. This concept is discussed further here.
- #13 At least 1 mm deep Present in ≥ 2 continuous leads that have dominant R waves (R/S ratio > 1) Dynamic — not present on old ECG or changing over time T-wave inversion can be a normal variant in III, aVR and V1
- #15 There are deep, symmetrical T wave inversions throughout the anterolateral leads (V1-6, I, aVL).
- #17 Wellens’ syndrome is a pattern of deeply inverted or biphasic T waves in V2-3, which is highly specific for a critical stenosis of the left anterior descending artery (LAD). Patients may be pain free by the time the ECG is taken and have normally or minimally elevated cardiac enzymes; however, they are at extremely high risk for extensive anterior wall MI within the next few days to weeks. Due to the critical LAD stenosis, these patients usually require invasive therapy, do poorly with medical management and may suffer MI or cardiac arrest if inappropriately stress tested A sudden occlusion of the LAD, causing a transient anterior STEMI. The patient has chest pain & diaphoresis. This stage may not be successfully captured on an ECG recording. Re-perfusion of the LAD (e.g. due to spontaneous clot lysis or prehospital aspirin). The chest pain resolves. ST elevation improves and T waves become biphasic or inverted. The T wave morphology is identical to patients who reperfuse after a successful PCI. If the artery remains open, the T waves evolve over time from biphasic to deeply inverted. The coronary perfusion is unstable, however, and the LAD can re-occlude at any time. If this happens, the first sign on the ECG is an apparent normalisation of the T waves — so-called “pseudo-normalisation”. The T waves switch from biphasic/inverted to upright and prominent. This is a sign of hyperacute STEMI and is usually accompanied by recurrence of chest pain, although the ECG changes can precede the symptoms. If the artery remains occluded, the patient now develops an evolving anterior STEMI. Alternatively, a “stuttering” pattern may develop, with intermittent reperfusion and re-occlusion. This would manifest as alternating ECGs demonstrating Wellens’ and pseudonormalisation/STEMI patterns.
- #21 Markedly increased LV voltages: S wave in V1 + R wave in V6 > 35 mm; R wave in aVL > 11 mm. Increased R wave peak time: the upstroke of the QRS complex is slurred in V5-6, resulting in minor QRS broadening. Left ventricular strain pattern: T wave inversion in the lateral leads V5-6, I and aVL. Left axis deviation. Signs of left atrial enlargement.
- #24 Prolonged PR interval. Broad, bizarre QRS complexes — these merge with both the preceding P wave and subsequent T wave. Peaked T waves.