Questions and Answers
What are the components of ECG?
What does the P Wave represent?
Atrial depolarization
What occurs during the PR segment?
Electrical inactivity between the P wave and the QRS complex
What does the QRS complex represent?
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What is indicated by a wide QRS?
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What does the T wave represent?
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What is the ST segment?
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The _____ uses heart rate as one of three criteria to identify treatable arrhythmias.
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How do you calculate heart rate using the Six Second Strip Method?
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What do you assess to determine if the rhythm is regular?
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What indicates a QRS complex is wide?
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How is the width of the QRS complex calculated?
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What indicates a normal QRS width?
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What must be verified to assess if every QRS is associated with a P wave?
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Study Notes
Components of ECG
- ECG consists of P wave, PR segment, QRS complex, T wave, and ST segment.
P Wave
- First wave in ECG sequence, indicating atrial depolarization.
- Typically shows an upward deflection.
PR Segment
- Represents electrical inactivity between P wave and QRS complex.
- Indicates conduction delay between AV node and Bundle of HIS, allowing atrial contraction before ventricular contraction.
- May be indistinguishable at high heart rates.
QRS Complex
- Reflects ventricular depolarization; larger than P wave due to greater ventricular muscle mass.
- Shows speed and direction of electrical impulse through ventricles; wide QRS signifies poor conduction and pumping strength.
QRS Appearance
- Q wave is present if the first deflection points downward.
- R wave denotes the first upward deflection in the complex.
- S wave follows R wave with a downward deflection.
T Wave
- Represents ventricular repolarization; heart reset for receiving new impulses.
- Cannot respond to another impulse until repolarization finishes; may appear elevated or inverted.
ST Segment
- Lies between the end of the QRS complex and the beginning of the T wave.
- Should align with the baseline in a healthy heart rhythm.
Interpreting ECG
- Key assessment questions:
- What is the heart rate?
- Is the rhythm regular?
- Is the QRS complex wide?
- Does every QRS have a corresponding P wave?
Importance of Heart Rate
- LifeVest monitors heart rate as one of three criteria for identifying treatable arrhythmias.
- Treatment thresholds are evaluated for ventricular tachycardia (VT) and ventricular fibrillation (VF) based on heart rate.
Six Second Strip Method
- Count number of QRS complexes over a six-second interval.
- Multiply the count by ten to estimate heart rate.
Rhythm Regularity
- Examine R-R intervals, the distance between R waves.
- Consistent R-R intervals indicate a regular rhythm, crucial for diagnosing arrhythmias.
Measuring QRS Width
- Wide QRS complex suggests the rhythm may originate in the ventricles.
- QRS width measured from the start of Q or R wave to the end of S wave.
Calculating QRS Width
- Count small boxes between Q (or R) and S waves; multiply by 0.04 seconds.
- Each small box represents 0.04 seconds.
Normal QRS
- A normal QRS width is ≤ 0.12 seconds (3 small boxes).
- Indicates electrical impulses come from above the ventricles through the AV node.
Wide QRS
- Defined as QRS width > 0.12 seconds (3 small boxes).
- Can result from conduction delays in ventricles or originate from ventricles themselves.
- The association of P waves and the QRS width aids in diagnosing the cause.
Associating QRS and P Wave
- Check if each QRS complex is preceded by a P wave.
- Ensure consistency of the PR interval between complexes.
- Relationship between QRS and P wave, along with QRS width, helps infer the rhythm's origin.
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Description
Test your knowledge on the components of ECG with these flashcards. Each card focuses on fundamental aspects such as the P Wave and PR segment, essential for understanding cardiac electrical activity. Perfect for med students and healthcare professionals.
