Explain 10 commem ECG changes in casaulty
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10 Common ECG Changes in Casualty (Emergency Department)
Here are the 10 most important ECG changes encountered in the casualty/ED, with the clinical context and key recognition features for each.
1. ST-Segment Elevation - STEMI
What to look for: ST elevation ≥1 mm in 2 or more contiguous leads (or ≥2 mm in V1-V3). The elevation is typically convex ("tombstone" morphology in acute infarct).
Location-based lead groups (from Tintinalli's Emergency Medicine):
| Infarct Territory | Leads with ST Elevation |
|---|---|
| Anteroseptal | V1, V2, ± V3 |
| Anterior | V1-V4 |
| Anterolateral | V1-V6, I, aVL |
| Lateral | I, aVL |
| Inferior | II, III, aVF |
| Right ventricular | II, III, aVF + ST elevation in V3R-V6R |
| Posterior | Tall R wave in V1-V2, R/S ≥ 1 (mirror image) |
Pearls: Reciprocal ST depression in opposite leads confirms ischemia and indicates larger injury zone and worse prognosis. Always obtain a right-sided ECG for inferior STEMI to rule out RV infarction. Get initial ECG within 10 minutes of arrival.
- Tintinalli's Emergency Medicine, Table 49-4
2. ST-Segment Depression - Subendocardial Ischemia / NSTEMI
What to look for: Horizontal or downsloping ST depression ≥0.5-1 mm in 2 or more contiguous leads.
Clinical significance: ST depression indicates subendocardial ischemia. It can appear as reciprocal change opposite a STEMI or as a primary finding in NSTEMI/unstable angina. Downsloping depression carries worse prognosis than upsloping. Leads V1-V3 showing ST depression may represent a posterior STEMI - always posterior leads in this scenario.
Causes in ED besides ischemia: Hypokalemia, digoxin effect, cor pulmonale, right heart strain, early repolarization.
- Tintinalli's Emergency Medicine, Table 49-6
3. Pathological Q Waves - Established Infarction
What to look for: Q wave ≥ 0.04 seconds (1 small square) wide AND ≥ 25% of the height of the following R wave, in 2 contiguous leads.
Significance: Q waves develop over hours to days after full-thickness (transmural) infarction as dead myocardium no longer generates electrical activity, and the vector swings away from that territory. In the acute setting, Q waves alongside ST elevation indicate established or evolving infarction. An isolated Q wave in lead III is normal; Q waves in II, III, and aVF together are pathological.
4. T-Wave Inversion - Ischemia / Wellens' Syndrome
What to look for: Deep, symmetrical T-wave inversions, particularly in precordial leads.
Wellens' Syndrome is a pattern of T-wave changes in V2-V3 (sometimes V1-V4) indicating critical left anterior descending (LAD) artery stenosis, even when the patient is pain-free at time of ECG:
- Type A (25%): Biphasic T waves (initially positive then negative) in V2-V3
- Type B (75%): Deep, symmetrical T-wave inversions in V2-V3
Significance: 15% of patients presenting with unstable angina will show Wellens' sign. These patients have high risk of acute anterior MI and need early interventional management - do NOT stress test them.
Other causes of T-wave inversion in casualty: Pulmonary embolism (right precordial leads), raised intracranial pressure, myocarditis, RV strain.
- Tintinalli's Emergency Medicine, p. 381
5. Hyperacute T Waves - Very Early STEMI
What to look for: Tall, broad, peaked ("hyperacute") T waves in the distribution of ischemia - often the first ECG sign of STEMI before ST elevation develops.
Significance: Hyperacute T waves appear within the first few minutes of coronary occlusion. They can be easily missed or dismissed as a normal variant. Any patient with symptoms and tall peaked T waves over a coronary distribution warrants serial ECGs and urgent assessment for reperfusion.
6. Peaked T Waves Progressing to Sinusoidal Pattern - Hyperkalemia
What to look for (sequential with rising K+):
- Tall, narrow, peaked ("tented") T waves - earliest sign (K+ ~5.5-6.5 mEq/L)
- Prolonged PR interval
- Widened QRS complex
- Flattened/absent P waves
- Sine-wave pattern (QRS-T fusion)
- Ventricular fibrillation or asystole
A stat ECG is mandatory in all hyperkalemic patients; if ECG changes are present, emergency treatment must begin immediately even before lab results return (e.g., dialysis patients). Death is usually from diastolic arrest or VF.
- Tintinalli's Emergency Medicine, p. 132
7. Prolonged QT Interval - Risk of Torsades de Pointes
What to look for: QTc (corrected QT) > 450 ms in men, > 470 ms in women. Measure from beginning of Q wave to end of T wave; correct using Bazett's formula (QTc = QT / √RR).
Common causes in ED (from Tintinalli's):
- Antiarrhythmics: Amiodarone, sotalol, quinidine
- Antipsychotics: Haloperidol, droperidol, quetiapine
- Antibiotics: Macrolides, fluoroquinolones
- Electrolytes: Hypokalemia, hypomagnesemia, hypocalcemia
- Others: Cocaine, methadone, tricyclic antidepressants
Significance: Prolonged QT can degenerate into torsades de pointes (polymorphic VT) - a potentially fatal arrhythmia. Treat precipitating cause; IV magnesium sulfate is first-line for torsades.
8. Right Heart Strain Pattern - Massive Pulmonary Embolism
What to look for:
- S1Q3T3 pattern: S wave in lead I, Q wave in lead III, T-wave inversion in lead III
- New right bundle branch block (RBBB)
- T-wave inversions in right precordial leads (V1-V4)
- Sinus tachycardia (most common ECG finding in PE)
- Right axis deviation
Significance: These changes reflect acute right ventricular pressure overload from a massive PE. A new RBBB in the setting of possible PE suggests RV strain and severe pulmonary hypertension. No single ECG finding is sensitive or specific for PE, but the combination in the right clinical context (dyspnea, hypoxia, pleuritic chest pain) should prompt urgent CT pulmonary angiography.
- Goldman-Cecil Medicine; Tintinalli's Emergency Medicine, Table 49-6
9. Widespread Saddle-Shaped ST Elevation + PR Depression - Pericarditis
What to look for:
- Stage 1 (acute): Diffuse concave ("saddle-shaped") ST elevation in almost all leads except aVR and V1; PR depression in most leads; PR elevation in aVR
- Stage 2: ST normalises, T waves flatten
- Stage 3: T-wave inversions (can mimic ischemia)
- Stage 4: ECG normalises
Distinguishing from STEMI:
-
Pericarditis: concave ("smiley face") ST elevation, diffuse (multiple territories), PR depression, no reciprocal ST depression (except aVR)
-
STEMI: convex ("frowning") ST elevation, localised to one territory, reciprocal depression
-
Tintinalli's Emergency Medicine, Table 49-6
10. Osborn (J) Waves - Hypothermia
What to look for: A distinctive positive deflection (notch or hump) at the junction of the QRS and ST segment (the J point), best seen in leads II and V5-V6. Also: bradycardia, prolonged PR/QRS/QT intervals, atrial fibrillation with slow ventricular response, muscle tremor artifact.
Temperature correlation:
- Osborn waves appear at core temperature < 32°C
- AF is common at < 30°C
- VF risk increases at < 28°C
Significance: Osborn waves are pathognomonic of hypothermia but can be misread by automated ECG systems as "injury current." Any patient with unexplained bradycardia, AF, or broad complex in the context of cold exposure should have a core temperature measured. "You are not dead until you are warm and dead" - resuscitation should continue until rewarming is achieved.
- Tintinalli's Emergency Medicine, Figure 209-1; Harrison's Principles of Internal Medicine 22E
Quick Reference Summary
| # | ECG Change | Key Condition |
|---|---|---|
| 1 | ST elevation | STEMI |
| 2 | ST depression | NSTEMI / subendocardial ischemia |
| 3 | Pathological Q waves | Established MI |
| 4 | T-wave inversion (V2-V3) | Wellens' syndrome / LAD stenosis |
| 5 | Hyperacute T waves | Earliest STEMI |
| 6 | Peaked T waves → sine wave | Hyperkalemia |
| 7 | Prolonged QTc | Drug-induced / electrolyte TdP risk |
| 8 | S1Q3T3 + RBBB | Massive PE |
| 9 | Saddle ST elevation + PR depression | Acute pericarditis |
| 10 | Osborn (J) waves | Hypothermia |
Key principle from Tintinalli's: The 12-lead ECG is the single best test to identify patients with AMI on ED presentation. Obtain and interpret it within 10 minutes of arrival for any patient with symptoms suggestive of myocardial ischemia.
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