Podcast
Questions and Answers
What is the normal QRS axis range?
What is the normal QRS axis range?
What is indicated by a left axis deviation?
What is indicated by a left axis deviation?
Which method relies on Lead I and aVF for axis estimation?
Which method relies on Lead I and aVF for axis estimation?
Right axis deviation can be caused by left ventricular hypertrophy.
Right axis deviation can be caused by left ventricular hypertrophy.
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What do you look for in the isoelectric lead?
What do you look for in the isoelectric lead?
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Which condition is associated with extreme axis deviation?
Which condition is associated with extreme axis deviation?
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Axis deviation can occur due to __________ or right ventricular hypertrophy.
Axis deviation can occur due to __________ or right ventricular hypertrophy.
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What does SAM represent in ECG analysis?
What does SAM represent in ECG analysis?
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Which lead is part of the three lead analysis alongside Lead I and aVF?
Which lead is part of the three lead analysis alongside Lead I and aVF?
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Study Notes
ECG Axis Interpretation Overview
- Normal Axis: QRS axis between -30° and +90°.
- Left Axis Deviation (LAD): QRS axis less than -30°.
- Right Axis Deviation (RAD): QRS axis greater than +90°.
- Extreme Axis Deviation (Northwest Axis): QRS axis between -90° and 180°.
Methods of ECG Axis Interpretation
- Quadrant Method: Utilizes Lead I and aVF.
- Three Lead Analysis: Involves Lead I, Lead II, and aVF.
- Isoelectric Lead Analysis: Identifies the axis with isoelectric leads.
- Super SAM the Axis Man: A mnemonic for easier conceptualization of axis.
Method 1: The Quadrant Method
- Analyzes QRS complexes in Lead I and Lead aVF.
- Positive QRS in Lead I aligns the axis with Lead I.
- Positive QRS in Lead aVF aligns the axis with Lead aVF.
- Combination of leads establishes the axis quadrant (normal, RAD, or LAD).
Method 2: Three Lead Analysis
- Integrates Lead II analysis alongside Lead I and aVF.
- Determines axis using positive QRS readings from all three leads.
- Positive readings in Lead I and II suggest an axis between -30° and +90°.
- Enhances accuracy in distinguishing pathological conditions.
Method 3: Isoelectric Lead Analysis
- Uses the isoelectric lead to refine axis estimation.
- Positive QRS indicates alignment with that lead.
- Negative QRS means the axis points opposite to that lead.
- Isoelectric (equiphasic) QRS lead indicates the axis is at 90° to that lead.
- Steps include identifying the isoelectric lead, locating positive leads, and calculating the axis direction.
Causes of Axis Deviation
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Right Axis Deviation:
- Right ventricular hypertrophy, pulmonary embolism, lateral STEMI.
- Chronic lung disease, hyperkalemia, sodium-channel blockade.
- Dextrocardia and various ectopies.
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Left Axis Deviation:
- Left ventricular hypertrophy, left bundle branch block, inferior MI.
- Ventricular pacing/ectopy and certain atrial septal defects.
-
Extreme Axis Deviation:
- Associated with ventricular rhythms, severe right ventricular hypertrophy, and hyperkalemia.
Super-Axis Man (SAM)
- Visual tool for understanding ECG axis.
- Concept involves drawing a character with directional arms representing leads.
- Labels represent key leads:
- Right Arm (aVR), Left Arm (aVL), Fiddly-bits (aVF).
- Tickling stick for Lead I and supporting splints for Leads II and III.
- Degrees marked at significant points: 0°, -30°, +60°, +90°, +120°, etc.
- Provides an engaging way to visualize axis determination.
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Description
This quiz covers the interpretation of ECG axis using diagrams and definitions. Learn about normal axis, left and right axis deviations, as well as extreme axis deviations. Test your knowledge on the methods of analyzing the QRS axis in frontal leads.
