Podcast
Questions and Answers
What is the formula to calculate a regular heart rate from an ECG?
What is the formula to calculate a regular heart rate from an ECG?
What is the significance of a PR interval less than 120 ms?
What is the significance of a PR interval less than 120 ms?
Which of the following would indicate Left Axis Deviation (LAD) on an ECG?
Which of the following would indicate Left Axis Deviation (LAD) on an ECG?
What is the significance of different P wave morphologies in an ECG?
What is the significance of different P wave morphologies in an ECG?
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What is the range of the normal axis on an ECG?
What is the range of the normal axis on an ECG?
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Which of the following conditions is associated with a prolonged PR interval (>200ms or 0.2 sec)?
Which of the following conditions is associated with a prolonged PR interval (>200ms or 0.2 sec)?
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What is the degree of lead I in the Hexaxial Reference System?
What is the degree of lead I in the Hexaxial Reference System?
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What is the significance of a depressed TP segment in an ECG?
What is the significance of a depressed TP segment in an ECG?
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Study Notes
ECG Analysis
-
Rate Calculation
- Regular rate: divide 300 by the number of big boxes or 1500 by the number of small boxes
- Irregular rate: multiply the number of QRS complexes in the rhythm strip by 6
- Ventricular heart rate: measure the number of boxes between adjacent QRS complexes
- Atrial heart rate: measure the number of boxes between adjacent P waves
Rhythm/Regularity
- No specific details mentioned in the text
P Waves
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Three Key Questions
- Are P waves upright in leads I, II, and aVF?
- Are P wave morphologies the same or different?
- Is there any evidence of atrial enlargement?
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Different P Wave Morphologies
- May indicate abnormalities in rhythms like premature atrial contractions (PACs) or multifocal atrial tachycardia (MAT)
PR Intervals
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PR Interval Interpretation
- Less than 120 ms: possible Wolff-Parkinson-White (WPW) syndrome
- Prolonged (>200 ms or 0.2 sec): possible 1st degree AV Block
- Elevated TP segment: atrial infarction
- Depressed TP segment: pericarditis
Axis
-
Hexaxial Reference System
- Lead I: 0 degrees
- Lead II: +60 degrees
- Lead III: +120 degrees
- Lead aVF: +90 degrees
- Lead aVR: -150 degrees
- Lead aVL: -30 degrees
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Normal Axis
- Range: -30 degrees to +90 degrees
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Left Axis Deviation (LAD)
- Range: -30 degrees to -90 degrees
- Indicates inferior MI, left bundle branch block (LBBB), or left ventricular hypertrophy (LVH)
-
Right Axis Deviation (RAD)
- Range: +90 degrees to +180 degrees
- Indicates lateral MI, right ventricular hypertrophy, or pulmonary embolism
-
Northwest/Extreme Axis (NW)
- Range: +/-180 degrees to -90 degrees
- Indicates apical MI, right ventricular hypertrophy (RVH), hyperkalemia, or ventricular tachycardia (VT)
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Determining Axis
- The lead with the greatest deflection of electrical current determines the axis
- The lead perpendicular to this lead should have a depolarization that is either flat-lined or balanced in terms of negative and positive current
QRS Complex
-
QRS Complex Analysis
- Examine QRS complex duration
- If duration is wide, examine morphology, especially in V1-V6
- Assess voltage (increased or low)
-
QRS Complex Duration
- Normal: 0.12 seconds (indicates RBBB or LBBB)
- Measured from the beginning of QRS to the end
- Narrow QRS indicates intact conduction through the His/Purkinje system
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Description
Analyze and interpret an electrocardiogram (ECG) incorporating various features including rate, rhythm, axis, P waves, PR interval, and QRS complex. Learn how to calculate regular and irregular heart rates, and understand the significance of each component.
